diff --git a/imperative/python/megengine/utils/profiler.py b/imperative/python/megengine/utils/profiler.py
index ae70da26fd18abf31bc676a6d22af040a2bc07b8..cf8fd518fa6adb1113104fd4feb78f54ce29b0fe 100644
--- a/imperative/python/megengine/utils/profiler.py
+++ b/imperative/python/megengine/utils/profiler.py
@@ -7,9 +7,14 @@
 # software distributed under the License is distributed on an
 # "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 import json
-from contextlib import contextmanager
+import os
+import re
+from contextlib import ContextDecorator, contextmanager
+from functools import wraps
 from typing import List
+from weakref import WeakSet
 
+from .. import _atexit
 from ..core._imperative_rt.core2 import (
     pop_scope,
     push_scope,
@@ -17,9 +22,13 @@ from ..core._imperative_rt.core2 import (
     stop_profile,
     sync,
 )
+from ..logger import get_logger
 
+_running_profiler = None
+_living_profilers = WeakSet()
 
-class Profiler:
+
+class Profiler(ContextDecorator):
     r"""
     Profile graph execution in imperative mode.
 
@@ -35,9 +44,10 @@ class Profiler:
         from megengine.utils.profiler import Profiler
 
         # With Learnable Parameters
+        profiler = Profiler()
         for iter in range(0, 10):
             # Only profile record of last iter would be saved
-            with Profiler("profile"):
+            with profiler:
                 # your code here
 
         # Then open the profile file in chrome timeline window
@@ -45,46 +55,105 @@ class Profiler:
 
     CHROME_TIMELINE = "chrome_timeline.json"
 
-    COMMAND = 1 << 0
-    OPERATOR = 1 << 1
-    TENSOR_LIFETIME = 1 << 2
-    TENSOR_PROP = 1 << 3
-    SYNC = 1 << 4
-    SCOPE = 1 << 5
-    ALL = (1 << 6) - 1
+    valid_options = {"sample_rate": 0, "profile_device": 1, "num_tensor_watch": 10}
+    valid_formats = {"chrome_timeline.json", "memory_flow.svg"}
 
     def __init__(
         self,
         path: str = "profile",
-        format: str = CHROME_TIMELINE,
-        *,
-        topic=OPERATOR | SCOPE,
-        align_time=True,
-        show_operator_name=True
+        format: str = "chrome_timeline.json",
+        formats: List[str] = None,
+        **kwargs
     ) -> None:
-        self._path = path
-        self._format = format
-        self._options = {
-            "topic": int(topic),
-            "align_time": int(align_time),
-            "show_operator_name": int(show_operator_name),
-        }
+        if not formats:
+            formats = [format]
 
-    def __enter__(self):
+        assert not isinstance(formats, str), "formats excepts list, got str"
+
+        for format in formats:
+            assert format in Profiler.valid_formats, "unsupported format {}".format(
+                format
+            )
+
+        self._path = path
+        self._formats = formats
+        self._options = {}
+        for opt, optval in Profiler.valid_options.items():
+            self._options[opt] = int(kwargs.pop(opt, optval))
+        self._pid = "<PID>"
+
+    @property
+    def path(self):
+        if len(self._formats) == 0:
+            format = "<FORMAT>"
+        elif len(self._formats) == 1:
+            format = self._formats[0]
+        else:
+            format = "{" + ",".join(self._formats) + "}"
+        return self.format_path(self._path, self._pid, format)
+
+    @property
+    def directory(self):
+        return self._path
+
+    @property
+    def formats(self):
+        return list(self._formats)
+
+    def start(self):
+        global _running_profiler
+
+        assert _running_profiler is None
+        _running_profiler = self
+        self._pid = os.getpid()
         start_profile(self._options)
         return self
 
-    def __exit__(self, val, tp, trace):
-        stop_profile(self._path, self._format)
-        # dump is async, so it's necessary to sync interpreter
+    def stop(self):
+        global _running_profiler
+
+        assert _running_profiler is self
+        _running_profiler = None
         sync()
+        self._dump_callback = stop_profile()
+        self._pid = os.getpid()
+        _living_profilers.add(self)
+
+    def dump(self):
+        if self._dump_callback is not None:
+            if not os.path.exists(self._path):
+                os.makedirs(self._path)
+            if not os.path.isdir(self._path):
+                get_logger().warning(
+                    "{} is not a directory, cannot write profiling results".format(
+                        self._path
+                    )
+                )
+                return
+            for format in self._formats:
+                path = self.format_path(self._path, self._pid, format)
+                get_logger().info("process {} generating {}".format(self._pid, format))
+                self._dump_callback(path, format)
+                get_logger().info("profiling results written to {}".format(path))
+            self._dump_callback = None
+            _living_profilers.remove(self)
+
+    def format_path(self, path, pid, format):
+        return os.path.join(path, "{}.{}".format(pid, format))
+
+    def __enter__(self):
+        self.start()
+
+    def __exit__(self, val, tp, trace):
+        self.stop()
 
     def __call__(self, func):
-        def wrapper(*args, **kwargs):
-            with self:
-                return func(*args, **kwargs)
+        func = super().__call__(func)
+        func.__profiler__ = self
+        return func
 
-        return wrapper
+    def __del__(self):
+        self.dump()
 
 
 @contextmanager
@@ -94,16 +163,77 @@ def scope(name):
     pop_scope(name)
 
 
-profile = Profiler
+def profile(*args, **kwargs):
+    if len(args) == 1 and len(kwargs) == 0 and callable(args[0]):
+        return Profiler()(args[0])
+    return Profiler(*args, **kwargs)
+
+
+def merge_trace_events(directory: str):
+    names = filter(
+        lambda x: re.match(r"\d+\.chrome_timeline\.json", x), os.listdir(directory)
+    )
+
+    def load_trace_events(name):
+        with open(os.path.join(directory, name), "r", encoding="utf-8") as f:
+            return json.load(f)
+
+    def find_metadata(content):
+        if isinstance(content, dict):
+            assert "traceEvents" in content
+            content = content["traceEvents"]
+        if len(content) == 0:
+            return None
+        assert content[0]["name"] == "Metadata"
+        return content[0]["args"]
+
+    contents = list(map(load_trace_events, names))
+
+    metadata_list = list(map(find_metadata, contents))
+
+    min_local_time = min(
+        map(lambda x: x["localTime"], filter(lambda x: x is not None, metadata_list))
+    )
+
+    events = []
+
+    for content, metadata in zip(contents, metadata_list):
+        local_events = content["traceEvents"]
+        if len(local_events) == 0:
+            continue
+
+        local_time = metadata["localTime"]
+        time_shift = local_time - min_local_time
+
+        for event in local_events:
+            if "ts" in event:
+                event["ts"] = int(event["ts"] + time_shift)
+
+        events.extend(filter(lambda x: x["name"] != "Metadata", local_events))
+
+    result = {
+        "traceEvents": events,
+    }
+
+    path = os.path.join(directory, "merge.chrome_timeline.json")
+
+    with open(path, "w") as f:
+        json.dump(result, f, ensure_ascii=False, separators=(",", ":"))
+
+    get_logger().info("profiling results written to {}".format(path))
+
+
+def is_profiling():
+    return _running_profiler is not None
+
+
+def _stop_current_profiler():
+    global _running_profiler
+    if _running_profiler is not None:
+        _running_profiler.stop()
+    living_profilers = [*_living_profilers]
+    for profiler in living_profilers:
+        profiler.dump()
 
 
-def merge_trace_events(sources: List[str], target: str):
-    names = list(map(lambda x: x + ".chrome_timeline.json", sources))
-    result = []
-    for name in names:
-        with open(name, "r", encoding="utf-8") as f:
-            content = json.load(f)
-            for entry in content:
-                result.append(entry)
-    with open(target + ".chrome_timeline.json", "w") as f:
-        json.dump(result, f, ensure_ascii=False, indent=4)
+_atexit(_stop_current_profiler)
diff --git a/imperative/python/src/tensor.cpp b/imperative/python/src/tensor.cpp
index 28357b22657a45504173108b2ebee5be1faad61e..0ed762f5f49cbe63456a279373b10d66cca44198 100644
--- a/imperative/python/src/tensor.cpp
+++ b/imperative/python/src/tensor.cpp
@@ -13,6 +13,7 @@
 #include "megbrain/common.h"
 #include "megbrain/imperative/ops/utility.h"
 #include "megbrain/imperative/ops/backward_graph.h"
+#include "megbrain/imperative/profiler.h"
 #include "megbrain/opr/io.h"
 
 #include "./tensor.h"
@@ -927,9 +928,23 @@ void init_tensor(py::module m) {
     m.def("pop_scope",
           [](std::string name) { interpreter_for_py->pop_scope(name); });
     m.def("start_profile",
-          [](std::unordered_map<std::string, int> option) { return interpreter_for_py->start_profile(option); });
+          [](imperative::Profiler::options_t options) {
+              interpreter_for_py->sync();
+              imperative::Profiler::load_options(std::move(options));
+              imperative::Profiler::start_profile();
+              interpreter_for_py->start_profile();
+          });
     m.def("stop_profile",
-          [](std::string basename, std::string format) { interpreter_for_py->stop_profile(basename, format); });
+          []() -> std::function<void(std::string, std::string)> {
+              interpreter_for_py->stop_profile();
+              interpreter_for_py->sync();
+              imperative::Profiler::stop_profile();
+              auto results = imperative::Profiler::collect();
+              auto options = imperative::Profiler::get_options();
+              return [results=std::move(results), options=std::move(options)](std::string basename, std::string format){
+                  imperative::Profiler::dump_profile(basename, format, results, options);
+              };
+          });
     m.def("sync",
           []() {
               interpreter_for_py->sync();
diff --git a/imperative/python/test/integration/test_profiler.py b/imperative/python/test/integration/test_profiler.py
index af8b5c469a85f33c7120da2c08398f4ea0fa8f22..32637d867ad2d7dd633e9e455873a225ddc96d87 100644
--- a/imperative/python/test/integration/test_profiler.py
+++ b/imperative/python/test/integration/test_profiler.py
@@ -8,6 +8,7 @@
 # "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied
 import json
 import os
+import tempfile
 
 import pytest
 
@@ -28,15 +29,18 @@ class Simple(Module):
 
 
 def test_profiler():
-    profile_prefix = "pytest_profile"
+    tempdir = tempfile.NamedTemporaryFile()
+    profile_prefix = tempdir.name
     profile_format = "chrome_timeline.json"
-    profile_path = "{}.{}".format(profile_prefix, profile_format)
-    with Profiler(profile_prefix, format=profile_format):
-        with scope("my_scope"):
-            oup = Simple()(tensor([1.23], dtype="float32"))
+    profile_path = os.path.join(
+        profile_prefix, "{}.{}".format(os.getpid(), profile_format)
+    )
+    with option("enable_host_compute", 0):
+        with Profiler(profile_prefix, format=profile_format):
+            with scope("my_scope"):
+                oup = Simple()(tensor([1.23], dtype="float32"))
     with open(profile_path, "r") as f:
         events = json.load(f)
-    os.remove(profile_path)
     prev_ts = {}
     scope_count = 0
     for event in events:
diff --git a/imperative/src/impl/interpreter/commands.h b/imperative/src/impl/interpreter/commands.h
index 88db1b065006849b58bbcf3d4a1733ccaa8d4dd8..be51a24bf90eee5dc7eda6b4831cb4d23ade47f1 100644
--- a/imperative/src/impl/interpreter/commands.h
+++ b/imperative/src/impl/interpreter/commands.h
@@ -13,11 +13,14 @@
 
 #include <string>
 #include <variant>
+#include <unordered_set>
 
 #include "megbrain/tensor.h"
 #include "megbrain/imperative/op_def.h"
 #include "megbrain/imperative/utils/to_string.h"
 
+#include "./tensor_info.h"
+
 namespace mgb::imperative {
 
 namespace interpreter::intl {
@@ -43,7 +46,7 @@ struct Put {
 };
 
 struct ApplyOp {
-    uint64_t id;
+    uint64_t id; //used by profiler to identify unique apply
     std::shared_ptr<OpDef> op;
     SmallVector<TensorInfo*> inputs;
     SmallVector<TensorInfo*> outputs;
@@ -143,7 +146,7 @@ struct SetOption {
 };
 
 struct StartProfile {
-    InterpreterProfiler* profiler;
+    std::unordered_set<TensorInfo*> capture_tensors;
 
     template <typename TFunctor>
     void get_props(TFunctor&& functor) const {}
@@ -154,14 +157,10 @@ struct StartProfile {
 };
 
 struct StopProfile {
-    std::string basename;
-    std::string format;
+    std::unordered_set<TensorInfo*> escape_tensors;
 
     template <typename TFunctor>
-    void get_props(TFunctor&& functor) const {
-        functor("basename", basename);
-        functor("format", format);
-    }
+    void get_props(TFunctor&& functor) const {}
 
     const char* get_name() const {
         return "StopProfile";
diff --git a/imperative/src/impl/interpreter/events.h b/imperative/src/impl/interpreter/events.h
deleted file mode 100644
index 48e96a20e91ab1d0d3ab761a18291393beda30af..0000000000000000000000000000000000000000
--- a/imperative/src/impl/interpreter/events.h
+++ /dev/null
@@ -1,75 +0,0 @@
-/**
- * \file imperative/src/impl/interpreter/events.h
- * MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
- *
- * Copyright (c) 2014-2020 Megvii Inc. All rights reserved.
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the License is distributed on an
- * "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- */
-
-#pragma once
-
-#include "./commands.h"
-#include "./tensor_info.h"
-
-namespace mgb::imperative::interpreter::intl {
-
-#define DEF_EVENT(X, ...) struct X##Event __VA_ARGS__;
-#define DEF_DUR_EVENT(X, ...) struct X##Event __VA_ARGS__; struct X##FinishEvent __VA_ARGS__;
-
-DEF_EVENT(Command, {
-    IdentifiedCommand icmd;
-});
-
-DEF_EVENT(CommandEnqueue, :CommandEvent {});
-DEF_EVENT(CommandExecute, :CommandEvent {});
-DEF_EVENT(CommandFinish, :CommandEvent {});
-DEF_DUR_EVENT(OpExecute, {
-    uint64_t id;
-    std::shared_ptr<OpDef> op;
-    SmallVector<uint64_t> inputs;
-    SmallVector<uint64_t> outputs;
-});
-DEF_DUR_EVENT(KernelExecute, {
-    uint64_t id;
-    std::shared_ptr<OpDef> op;
-    SmallVector<uint64_t> inputs;
-    SmallVector<uint64_t> outputs;
-});
-DEF_EVENT(TensorDeclare, {
-    uint64_t tensor_id;
-});
-DEF_EVENT(TensorProduce, {
-    uint64_t tensor_id;
-    TensorLayout layout;
-    CompNode device;
-});
-DEF_EVENT(TensorErase, {
-    uint64_t tensor_id;
-});
-DEF_EVENT(TensorGetProp, {
-    uint64_t tensor_id;
-    TensorInfo::Prop prop;
-    std::string prop_desc;
-});
-DEF_DUR_EVENT(TensorWaitProp, {
-    uint64_t tensor_id;
-    TensorInfo::Prop prop;
-    std::string prop_desc;
-});
-DEF_EVENT(TensorNotifyProp, {
-    uint64_t tensor_id;
-    TensorInfo::Prop prop;
-    std::string prop_desc;
-});
-DEF_DUR_EVENT(Sync, {});
-DEF_DUR_EVENT(Scope, {
-    std::string name;
-});
-DEF_DUR_EVENT(DeviceScope, {
-    std::string name;
-});
-
-}
diff --git a/imperative/src/impl/interpreter/interpreter_impl.cpp b/imperative/src/impl/interpreter/interpreter_impl.cpp
index 9c43eb133e424e1097977b746f1086d04a4160bc..5b5ec7c217d382532975c1f2033c9721ce0b1d35 100644
--- a/imperative/src/impl/interpreter/interpreter_impl.cpp
+++ b/imperative/src/impl/interpreter/interpreter_impl.cpp
@@ -20,19 +20,17 @@
 #include "megbrain/imperative/ops/opr_attr.h"
 #include "megbrain/imperative/utils/to_string.h"
 
+#include "../event_pool.h"
+#include "../op_trait.h"
+
 using namespace mgb;
 using namespace imperative;
 using namespace interpreter;
 using namespace interpreter::intl;
 
 #define RECORD_EVENT(type, ...) \
-    if (state.profiler->is_profiling()) { \
-        state.profiler->record_host<type>(type{__VA_ARGS__}); \
-    } \
-
-#define RECORD_DEVICE_EVENT(type, device, ...) \
-    if (state.profiler->is_profiling()) { \
-        state.profiler->record_device<type>((device), type{__VA_ARGS__}); \
+    if (Profiler::is_profiling()) { \
+        Profiler::record<type>(type{__VA_ARGS__}); \
     } \
 
 
@@ -46,6 +44,10 @@ namespace {
     };
 }
 
+namespace mgb {
+    using namespace profiler;
+}
+
 std::thread::id ChannelImpl::get_worker_tid() {
     return m_worker_state.tid;
 }
@@ -60,6 +62,7 @@ ChannelImpl::WorkerState& ChannelImpl::get_worker_state() {
     return m_worker_state;
 }
 
+// Do not use m_xxx_state directly
 #define m_channel_state
 #define m_worker_state
 
@@ -74,10 +77,16 @@ Interpreter& Interpreter::inst() {
 
 Handle ChannelImpl::put(const HostTensorND& value, bool no_cache) {
     mgb_assert(check_available(), "Channel already closed");
+    auto& state = get_channel_state();
+    state.scopes.push("Put");
+    auto info = put_impl(value, no_cache);
+    state.scopes.pop("Put");
+    return info;
+}
+
+TensorInfo* ChannelImpl::put_impl(const HostTensorND& value, bool no_cache) {
     auto info = alloc();
-    info->desc.layout = value.layout();
-    info->desc.comp_node = value.comp_node();
-    info->desc.value = value.proxy_to_default_cpu();
+    init(info, {value.layout(), value.comp_node(), value.proxy_to_default_cpu()});
     info->h_value = value;
     m_buffer.enqueue(Put{info, value, no_cache});
     if (m_async_level == 0) {
@@ -90,11 +99,15 @@ Handle ChannelImpl::put(const HostTensorND& value, bool no_cache) {
 Handle ChannelImpl::put(const DeviceTensorND& data) {
     auto& state = get_channel_state();
     mgb_assert(check_available(), "Channel already closed");
+    state.scopes.push("Put");
     auto info = alloc();
-    info->desc.layout = data.layout();
-    info->desc.comp_node = data.comp_node();
+    RECORD_EVENT(TensorCommandEvent, info->id, TensorCommandEvent::Put);
+    init(info, {data.layout(), data.comp_node()});
     info->ptr = Tensor::make(data);
-    RECORD_EVENT(TensorProduceEvent, info->id, info->desc.layout, info->desc.comp_node);
+    RECORD_EVENT(TensorProduceEvent, info->id, info->desc.layout, info->desc.comp_node, data.raw_ptr());
+    info->status = TensorInfo::Produced;
+    RECORD_EVENT(TensorCommandFinishEvent, info->id, TensorCommandFinishEvent::Put);
+    state.scopes.pop("Put");
     return info;
 }
 
@@ -148,7 +161,7 @@ void ChannelImpl::dispatch_default_cpu(
         SmallVector<Handle>* outputs) {
     auto& state = get_channel_state();
     auto [output_descs, validated] = OpDef::infer_output_attrs_fallible(*op, input_descs);
-    MGB_MARK_USED_VAR(validated);
+    RECORD_EVENT(ShapeInferEvent, validated);
 
     SmallVector<DeviceTensorND> input_tensornds;
     input_tensornds.reserve(input_descs.size());
@@ -166,6 +179,7 @@ void ChannelImpl::dispatch_default_cpu(
             if (info->ptr && info->ptr->try_get_value()) {
                 input_tensornds.emplace_back(info->ptr->get_value().proxy_to_default_cpu());
             } else {
+                // It's OK for SwapOut. We assign h_value before drop ptr
                 mgb_assert(!info->h_value.empty(), "inp->h_value is empty!");
                 input_tensornds.emplace_back(info->h_value.proxy_to_default_cpu());
             }
@@ -182,8 +196,7 @@ void ChannelImpl::dispatch_default_cpu(
         output_tensornds.emplace_back(HostTensorND(output_cn, desc.layout).proxy_to_default_cpu());
     }
 
-    auto apply_id = ++m_last_id;
-    RECORD_EVENT(OpExecuteEvent, apply_id, op, tinfo_to_tid(input_infos), {});
+    uint64_t op_id = Profiler::next_id();
 
     OpDef::apply_on_device_tensornd(*op, input_tensornds, &output_tensornds);
 
@@ -193,14 +206,20 @@ void ChannelImpl::dispatch_default_cpu(
         HostTensorND host_tensornd = HostTensorND::make_proxy(tensornd)
             .proxy_to_comp_node(output_cn);
         // use `put` for consistency
-        auto info = reinterpret_cast<TensorInfo*>(put(host_tensornd, false));
+        auto info = reinterpret_cast<TensorInfo*>(put_impl(host_tensornd, false));
         mgb_assert(info->desc.layout.ndim != 0);
         output_infos.push_back(info);
         outputs->push_back(info);
     }
-
-    RECORD_EVENT(OpExecuteFinishEvent, apply_id, op, 
-            tinfo_to_tid(input_infos), tinfo_to_tid(output_infos));
+    auto op_info_getter = [op]{
+        std::unordered_map<std::string, std::string> op_info;
+        auto props = OpDef::props(*op);
+        for (auto&& [key, value]: props) {
+            op_info[key] = value;
+        }
+        return op_info;
+    };
+    RECORD_EVENT(OpDispatchEvent, op_id, op->trait()->name, op_info_getter, tinfo_to_tid(input_infos), tinfo_to_tid(output_infos));
 }
 
 void ChannelImpl::dispatch_kernel(
@@ -209,15 +228,22 @@ void ChannelImpl::dispatch_kernel(
         const SmallVector<LogicalTensorDesc>& input_descs,
         SmallVector<Handle>* outputs) {
     auto& state = get_channel_state();
+    auto& options = state.options;
+
+    auto name = op->trait()->make_name(*op);
+    state.scopes.push(name);
+
     auto [output_descs, validated] = OpDef::infer_output_attrs_fallible(*op, input_descs);
+    RECORD_EVENT(ShapeInferEvent, validated);
 
-    ApplyOp cmd{++m_last_id, std::move(op)};
+    ApplyOp cmd{Profiler::next_id(), std::move(op)};
     cmd.inputs = std::move(input_infos);
     cmd.outputs.reserve(output_descs.size());
     outputs->reserve(output_descs.size());
-    for (auto&& desc : output_descs) {
+    for (int i = 0; i < output_descs.size(); ++i) {
+        auto&& desc = output_descs[i];
         auto info = alloc();
-        info->desc = desc;
+        init(info, desc);
         // make sure desc's value is consistent with h_value
         if (!info->desc.value.empty()) {
             info->h_value = HostTensorND::make_proxy(desc.value)
@@ -226,10 +252,19 @@ void ChannelImpl::dispatch_kernel(
         cmd.outputs.push_back(info);
         outputs->push_back(info);
     }
+    auto op_info_getter = [op=cmd.op]{
+        std::unordered_map<std::string, std::string> op_info;
+        auto props = OpDef::props(*op);
+        for (auto&& [key, value]: props) {
+            op_info[key] = value;
+        }
+        return op_info;
+    };
+    RECORD_EVENT(OpDispatchEvent, cmd.id, cmd.op->trait()->name, op_info_getter, tinfo_to_tid(cmd.inputs), tinfo_to_tid(cmd.outputs));
     m_buffer.enqueue(std::move(cmd));
-    if (!validated && state.options.async_level == 1) {
+    if (!validated && options.async_level == 1) {
         sync();
-    } else if (state.options.async_level == 0) {
+    } else if (options.async_level == 0) {
         sync();
         // check device error
         for (auto&& oup : *outputs) {
@@ -237,6 +272,7 @@ void ChannelImpl::dispatch_kernel(
             info->ptr->comp_node().sync();
         }
     }
+    state.scopes.pop(name);
 }
 
 SmallVector<Handle> ChannelImpl::apply_op(
@@ -282,31 +318,12 @@ SmallVector<Handle> ChannelImpl::apply_op(
 HostTensorND ChannelImpl::get_value(Handle handle) {
     mgb_assert(check_available(), "Channel already closed");
     auto& state = get_channel_state();
-    // TODO: maybe get_value should be done on host. i.e. delete GetValue
     mgb_assert(m_valid_handle.find(handle) != m_valid_handle.end(),
                "invalid handle: %p", handle);
     auto info = reinterpret_cast<TensorInfo*>(handle);
-    mgb_assert(!m_waitee);
     // donnot use info->value_fetched, it's unsafe
     mgb_assert(!info->invalid, "Invalid tensor, unable to get_value!");
-    std::unique_lock<decltype(m_mutex)> lock(m_mutex);
-    TensorPtr tensor_ptr = info->ptr;
-    auto value_fetched = [&]() {
-        return tensor_ptr && tensor_ptr->value_fetched();
-    };
-    if (!value_fetched()) {
-        m_waitee = info;
-        m_buffer.enqueue(GetValue{info});
-        RECORD_EVENT(TensorWaitPropEvent, info->id, TensorInfo::HostValue);
-        m_cv.wait(lock, [&]() {
-            check_worker_exc_unsafe();
-            tensor_ptr = info->ptr;
-            return value_fetched();
-        });
-        RECORD_EVENT(TensorWaitPropFinishEvent, info->id, TensorInfo::HostValue);
-        m_waitee = nullptr;
-    }
-    return tensor_ptr->get_value();
+    return wait_tensor(info, TensorProp::HostValue)->get_value();
 }
 
 TensorShape ChannelImpl::get_shape(Handle handle) {
@@ -318,18 +335,7 @@ TensorShape ChannelImpl::get_shape(Handle handle) {
     if (info->desc.layout.ndim != 0) {
         return info->desc.layout;
     }
-    std::unique_lock<decltype(m_mutex)> lock(m_mutex);
-    mgb_assert(!m_waitee);
-    m_waitee = info;
-    m_buffer.flush();
-    RECORD_EVENT(TensorWaitPropEvent, info->id, TensorInfo::Shape);
-    m_cv.wait(lock, [&]() {
-        check_worker_exc_unsafe();
-        return static_cast<bool>(info->ptr);
-    });
-    RECORD_EVENT(TensorWaitPropFinishEvent, info->id, TensorInfo::Shape);
-    m_waitee = nullptr;
-    TensorShape ret = info->ptr->layout();
+    TensorShape ret = wait_tensor(info, TensorProp::Shape)->layout();
     mgb_assert(ret.ndim != 0);
     return ret;
 }
@@ -340,7 +346,7 @@ DType ChannelImpl::get_dtype(Handle handle) {
     mgb_assert(m_valid_handle.find(handle) != m_valid_handle.end(),
                "invalid handle: %p", handle);
     auto info = reinterpret_cast<TensorInfo*>(handle);
-    RECORD_EVENT(TensorGetPropEvent, info->id, TensorInfo::DType);
+    RECORD_EVENT(TensorGetPropEvent, info->id, TensorProp::DType);
     auto ret = info->desc.layout.dtype;
     mgb_assert(ret.valid());
     return ret;
@@ -352,7 +358,7 @@ CompNode ChannelImpl::get_device(Handle handle) {
     mgb_assert(m_valid_handle.find(handle) != m_valid_handle.end(),
                "invalid handle: %p", handle);
     auto info = reinterpret_cast<TensorInfo*>(handle);
-    RECORD_EVENT(TensorGetPropEvent, info->id, TensorInfo::Device);
+    RECORD_EVENT(TensorGetPropEvent, info->id, TensorProp::Device);
     auto ret = info->desc.comp_node;
     mgb_assert(ret.valid());
     return ret;
@@ -364,28 +370,14 @@ DeviceTensorND ChannelImpl::get_dev_tensor(Handle handle) {
     mgb_assert(m_valid_handle.find(handle) != m_valid_handle.end(),
                "invalid handle: %p", handle);
     auto info = reinterpret_cast<TensorInfo*>(handle);
-    std::unique_lock<decltype(m_mutex)> lock(m_mutex);
-    mgb_assert(!m_waitee);
-    m_waitee = info;
-    m_buffer.flush();
-    RECORD_EVENT(TensorWaitPropEvent, info->id, TensorInfo::DevValue);
-    m_cv.wait(lock, [&]() {
-        check_worker_exc_unsafe();
-        return static_cast<bool>(info->ptr);
-    });
-    RECORD_EVENT(TensorWaitPropFinishEvent, info->id, TensorInfo::DevValue);
-    m_waitee = nullptr;
-    return info->ptr->dev_tensor();
+    return wait_tensor(info, TensorProp::DevValue)->dev_tensor();
 }
 
 void ChannelImpl::sync() {
     mgb_assert(check_available(), "Channel already closed");
     auto& state = get_channel_state();
     m_buffer.flush();
-    RECORD_EVENT(SyncEvent);
     m_worker.wait_all_task_finish();
-    CompNode::sync_all();
-    RECORD_EVENT(SyncFinishEvent);
     MGB_LOCK_GUARD(m_mutex);
     check_worker_exc_unsafe();
 }
@@ -419,14 +411,24 @@ void ChannelImpl::set_option(std::string name, size_t value) {
 
 TensorInfo* ChannelImpl::alloc() {
     auto& state = get_channel_state();
-    MGB_LOCK_GUARD(m_mutex);
-    auto info = m_pool.alloc();
-    m_valid_handle.insert(info);
-    info->id = m_last_id++;
-    RECORD_EVENT(TensorDeclareEvent, info->id);
+    auto info = [this]{
+        MGB_LOCK_GUARD(m_mutex);
+        return m_pool.alloc();
+    }();
+    info->id = Profiler::next_id();
+    if (Profiler::is_profiling()) {
+        info->name = state.scopes.next_tensor_name();
+    }
     return info;
 }
 
+void ChannelImpl::init(TensorInfo* info, LogicalTensorDesc desc) {
+    m_valid_handle.insert(info);
+    RECORD_EVENT(TensorDeclareEvent, info->id, info->name);
+    info->status = TensorInfo::Allocated;
+    info->desc = std::move(desc);
+}
+
 
 void ChannelImpl::do_drop(TensorInfo* ptr, bool user=false) {
     if (!ptr->producer) {
@@ -439,6 +441,7 @@ void ChannelImpl::do_drop(TensorInfo* ptr, bool user=false) {
         return;
     }
     ptr->evict_type = EvictType::DROP;
+    ptr->status = TensorInfo::Dropped;
     release_tensor(ptr);
 }
 
@@ -460,7 +463,8 @@ void ChannelImpl::free(TensorInfo* ptr) {
 }
 
 void ChannelImpl::recursive_free(TensorInfo* ptr) {
-    SmallVector<TensorInfo*> inps(0);
+    RECORD_EVENT(TensorCommandEvent, ptr->id, TensorCommandEvent::RecFree);
+    SmallVector<TensorInfo*> inps;
     if (ptr->producer) {
         for (auto i : ptr->producer->inputs) {
             if (i && --i->ref_cnt == 0) {
@@ -474,17 +478,23 @@ void ChannelImpl::recursive_free(TensorInfo* ptr) {
             recursive_free(i);
         }
     }
+    RECORD_EVENT(TensorCommandFinishEvent, ptr->id, TensorCommandFinishEvent::RecFree);
 }
 
 void ChannelImpl::real_free(TensorInfo* ptr) {
     auto& state = get_worker_state();
     MGB_LOCK_GUARD(m_mutex);
-    RECORD_EVENT(TensorEraseEvent, ptr->id);
     if (ptr->size_exceeds_thd(state.options.dtr_evictee_minimum_size)) {
         m_dtr.erase_candidate(ptr);
     }
     detach_users(ptr);
     ptr->detach_producer();
+    bool has_value = ptr->ptr != nullptr;
+    if (has_value) {
+        RECORD_EVENT(TensorReleaseEvent, ptr->id);
+    }
+    RECORD_EVENT(TensorEraseEvent, ptr->id, ptr->ptr_use_count);
+    ptr->status = TensorInfo::Deleted;
     m_pool.free(ptr);
 }
 
@@ -496,46 +506,48 @@ ChannelImpl::~ChannelImpl() {
 
 void ChannelImpl::produce_tensor(TensorInfo* dest, TensorPtr ptr, bool notice=true) {
     auto& state = get_worker_state();
-    auto lock = std::unique_lock<std::mutex>(m_mutex, std::defer_lock);
+    std::unique_lock<std::mutex> lock{m_mutex, std::defer_lock};
     if (notice) {
         lock.lock();
     }
     m_dtr.update_used_time(dest);
-    if (notice) {
-        RECORD_EVENT(TensorProduceEvent, dest->id, ptr->layout(), ptr->comp_node());
-    }
-    dest->value_fetched = ptr->value_fetched();
+    RECORD_EVENT(TensorProduceEvent, dest->id, ptr->layout(), ptr->comp_node(), ptr->dev_tensor().raw_ptr());
     // update tensor desc for static infer
     dest->desc.layout = ptr->layout();
     dest->desc.comp_node = ptr->comp_node();
     dest->memory = ptr->blob()->size();
     dest->ptr = std::move(ptr);
     dest->evict_type = EvictType::NONE;
+    dest->status = TensorInfo::Produced;
     if (notice && dest->size_exceeds_thd(state.options.dtr_evictee_minimum_size)) {
         m_dtr.insert_candidate(dest);
     }
-    if (notice && m_waitee == dest) {
-        m_cv.notify_all();
+    if (notice) {
+        notify_tensor_unsafe(dest);
     }
 }
 
 void ChannelImpl::release_tensor(TensorInfo* dest) {
+    RECORD_EVENT(TensorReleaseEvent, dest->id);
     MGB_LOCK_GUARD(m_mutex);
     dest->ptr.reset();
 }
 
 void ChannelImpl::regenerate(TensorInfo* dest) {
+    RECORD_EVENT(TensorCommandEvent, dest->id, TensorCommandEvent::ReGen);
     if (dest->evict_type == EvictType::DROP) {
         recompute(dest->producer);
     } else if (dest->evict_type == EvictType::SWAP) {
         produce_tensor(dest, Tensor::make(dest->h_value));
     }
+    RECORD_EVENT(TensorCommandFinishEvent, dest->id, TensorCommandFinishEvent::ReGen);
 }
 
 void ChannelImpl::do_apply_op(const ApplyOp& cmd) {
     using namespace ranges;
     using namespace ranges::views;
     auto& state = get_worker_state();
+    bool profiling_device = Profiler::is_profiling() && Profiler::get_option("profile_device", 0);
     uint64_t apply_id = cmd.id;
     SmallVector<TensorPtr> tensor_inputs;
     if (state.options.enable_dtr_auto_drop) {
@@ -545,33 +557,50 @@ void ChannelImpl::do_apply_op(const ApplyOp& cmd) {
         if (!i->ptr && i->evict_type != EvictType::NONE) {
             regenerate(i);
         }
-        // inputs.push_back(i->ptr);
         m_dtr.update_used_time(i);
     }
     tensor_inputs.reserve(cmd.inputs.size());
     // refcnt == 1, owners: [TensorInfo::ptr]
     for (auto i : cmd.inputs) {
         mgb_assert(i->ptr, "Invalid input tensor ptr!");
+        // refcnt ++, owners: [i->ptr, tensor_inputs]
         tensor_inputs.push_back(i->ptr);
     }
+    RECORD_EVENT(OpExecuteEvent, apply_id);
     // Begin profiling operator
-    SmallVector<CompNode> devices;
-    if (state.profiler->is_profiling()) {
+    SmallVector<std::pair<CompNode, uint64_t>> kernels;
+    if (profiling_device) {
+        // Collecting devices
+        SmallVector<CompNode> devices;
         for (auto&& i : concat(cmd.inputs, cmd.outputs)) {
             if (i != nullptr && count(devices, i->desc.comp_node) == 0) {
                 devices.push_back(i->desc.comp_node);
+                kernels.push_back({i->desc.comp_node, Profiler::next_id()});
             }
         }
     }
+    for (auto* input: cmd.inputs) {
+        auto input_id = input->id;
+        RECORD_EVENT(OpInputEvent, input_id);
+        RECORD_EVENT(TensorUsageEvent, input_id);
+        RECORD_EVENT(OpInputFinishEvent, input_id);
+    }
+    // Fused by command buffer. @see: CommandBuffer::fuse_del
+    // Now if dest is inplacable, it's refcnt would be decreased to 1 and owned by tensor_inputs after Del.
+    // Note for exprs like 'y = x op x', inplace is unsupported yet but Del would be also fused.
     for (auto* del : cmd.dels) {
+        // refcnt --, owners: [tensor_inputs]
+        // if it's decreased to 1, would be detected at @see: proxy_graph_detail::apply_on_physical_tensor
+        uint64_t del_id = del->id;
+        RECORD_EVENT(OpDelEvent, del_id);
         free(del);
+        RECORD_EVENT(OpDelFinishEvent, del_id);
     }
-    RECORD_EVENT(OpExecuteEvent, apply_id, cmd.op,
-            tinfo_to_tid(cmd.inputs), tinfo_to_tid(cmd.outputs));
-    for (auto&& device: devices) {
-        sync_device_scope(device);
-        RECORD_DEVICE_EVENT(KernelExecuteEvent, device, apply_id, cmd.op,
-                tinfo_to_tid(cmd.inputs), tinfo_to_tid(cmd.outputs));
+    // Before wait
+    //TODO: split operator wait and execute so that OpWait could be corrected recorded.
+    // Before execute
+    for (auto&& [device, kernel_id]: kernels) {
+        RECORD_EVENT(KernelExecuteEvent, apply_id, kernel_id, Timer::record_event(device));
     }
     if (state.options.enable_dtr_auto_drop && state.options.dtr_eviction_threshold > 0) {
         auto_evict();
@@ -579,20 +608,26 @@ void ChannelImpl::do_apply_op(const ApplyOp& cmd) {
     // Apply op
     // Here std::move is REQUIRED for removing duplicated references.
     auto tensor_outputs = OpDef::apply_on_physical_tensor(
-        *cmd.op, tensor_inputs);
+        *cmd.op, std::move(tensor_inputs));
     // After execute
-    for (auto&& device : devices) {
-        RECORD_DEVICE_EVENT(KernelExecuteFinishEvent, device, apply_id, cmd.op,
-                tinfo_to_tid(cmd.inputs), tinfo_to_tid(cmd.outputs));
+    for (auto&& [device, kernel_id]: kernels) {
+        RECORD_EVENT(KernelExecuteFinishEvent, apply_id, kernel_id, Timer::record_event(device));
     }
-    RECORD_EVENT(OpExecuteFinishEvent, apply_id, cmd.op,
-            tinfo_to_tid(cmd.inputs), tinfo_to_tid(cmd.outputs));
     // End profiling operator
     mgb_assert(tensor_outputs.size() == cmd.outputs.size());
     for (size_t i = 0; i < tensor_outputs.size(); ++i) {
         auto output = cmd.outputs[i];
-        if (output != nullptr && output->ptr == nullptr) {
+        if (output == nullptr) {
+            RECORD_EVENT(OpOutputEvent, 0);
+            RECORD_EVENT(OpOutputFinishEvent, 0);
+        } else if (output->ptr != nullptr) {
+            RECORD_EVENT(OpOutputEvent, output->id);
+            RECORD_EVENT(OpOutputFinishEvent, output->id);
+        } else {
+            RECORD_EVENT(OpOutputEvent, output->id);
             produce_tensor(output, tensor_outputs[i]);
+            RECORD_EVENT(OpOutputFinishEvent, output->id);
+            sample_on_device(output->desc.comp_node, false);
         }
     }
 
@@ -612,6 +647,8 @@ void ChannelImpl::do_apply_op(const ApplyOp& cmd) {
         }
         m_dtr.unpin(cmd.inputs);
     }
+    RECORD_EVENT(OpExecuteFinishEvent, apply_id);
+    // End profiling operator
 }
 
 void ChannelImpl::recompute(TensorInfo::ComputePath* path) {
@@ -637,6 +674,7 @@ void ChannelImpl::auto_evict() {
     }
     size_t current_memory = m_dtr.comp_node.get_used_memory();
     while (current_memory > state.options.dtr_eviction_threshold) {
+        sample_on_device(m_dtr.comp_node, false);
         auto best = m_dtr.find_best_tensor();
         if (!best) {
             if (!m_dtr.warn_printed) {
@@ -656,6 +694,7 @@ void ChannelImpl::auto_evict() {
         if (best->evict_type == EvictType::DROP) {
             m_dtr.update_dsu_after_evict(best);
         }
+        sample_on_device(m_dtr.comp_node, false);
     }
 }
 
@@ -665,6 +704,10 @@ void ChannelImpl::detach_users(TensorInfo* dest) {
         SmallVector<TensorInfo*> outputs = user->outputs;
         SmallVector<TensorInfo*> inputs = user->inputs;
         for (auto* output: outputs) {
+        // When a `ComputePath` is detach from it's input,
+        // there is no need to reserve it,
+        // so we detach all output of this path
+        // to decrease it's `ref_cnt` to zero.
             if (output == nullptr) {
                 continue;
             }
@@ -674,63 +717,79 @@ void ChannelImpl::detach_users(TensorInfo* dest) {
                 input->ref_cnt --;
             }
         }
+        // now user is dead
     }
-    mgb_assert(dest->users.size() == 0);
-    //dest->users.clear();
+    mgb_assert(dest->users.empty(), "ComputePath leaking");
 }
 
 bool ChannelImpl::check_available() {
     return !m_closed;
 }
 
-void ChannelImpl::sync_device_scope(CompNode device) {
-    auto& state = get_worker_state();
-    auto& prev = state.device_scope_map[device];
-    auto& current = state.scopes;
-    auto push_scope = [&](std::string name) {
-        RECORD_DEVICE_EVENT(DeviceScopeEvent, device, name);
-    };
-    auto pop_scope = [&](std::string name) {
-        RECORD_DEVICE_EVENT(DeviceScopeFinishEvent, device, name);
-    };
-    size_t similarity = 0;
-    for (size_t i = 0; i < prev.size() && i < current.size(); i++) {
-        if (prev[i] == current[i]) {
-            similarity++;
+TensorPtr ChannelImpl::wait_tensor(TensorInfo* info, TensorProp prop) {
+    m_buffer.flush();
+    std::unique_lock<decltype(m_mutex)> lock(m_mutex);
+    mgb_assert(!m_waitee, "duplicate waitee");
+    m_waitee = info;
+    m_waitee_id = Profiler::next_id();
+    RECORD_EVENT(TensorWaitPropEvent, info->id, m_waitee_id, prop);
+    bool require_host = prop == TensorProp::HostValue;
+    bool value_fetching = false;
+    m_cv.wait(lock, [&]() {
+        check_worker_exc_unsafe();
+        if (require_host) {
+            if (info->ptr && info->ptr->value_fetched()) {
+                return true;
+            }
+            if (!value_fetching) {
+                m_buffer.enqueue(GetValue{info});
+                value_fetching = true;
+            }
+            return false;
         } else {
-            break;
+            return static_cast<bool>(info->ptr);
         }
+    });
+    RECORD_EVENT(TensorWaitPropFinishEvent, info->id, m_waitee_id, prop, m_waitee == nullptr);
+    if (m_waitee != nullptr) {
+        mgb_assert(m_waitee == info, "waitee mismatch");
+        m_waitee = nullptr;
     }
-    while (prev.size() > similarity) {
-        pop_scope(prev.back());
-        prev.pop_back();
+    return info->ptr;
+}
+
+void ChannelImpl::notify_tensor_unsafe(TensorInfo* info) {
+    if (info == m_waitee) {
+        m_waitee = nullptr;
+        RECORD_EVENT(TensorNotifyPropEvent, info->id);
+        m_cv.notify_all();
     }
-    while (prev.size() < current.size()) {
-        prev.push_back(current[prev.size()]);
-        push_scope(prev.back());
+}
+
+std::unordered_set<TensorInfo*> ChannelImpl::collect_valid_tensors() {
+    std::unordered_set<TensorInfo*> valid_tensors;
+    for (auto* handle: m_valid_handle) {
+        auto* info = reinterpret_cast<TensorInfo*>(handle);
+        valid_tensors.insert(info);
+    //TODO: valid_tensors.insert({info, info->status});
     }
+    return valid_tensors;
 }
 
 void ChannelImpl::process_one_task(IdentifiedCommand& icmd) {
     using namespace ranges;
     using namespace ranges::views;
-
     auto& state = get_worker_state();
-    RECORD_EVENT(CommandExecuteEvent, icmd);
-    bool finished = false;
-    auto do_finish_command = [&]{
-        if (finished) {
-            return;
-        }
-        RECORD_EVENT(CommandFinishEvent, icmd);
-        finished = true;
-    };
+    auto& options = state.options;
     //TODO: remove std::visit for support osx 10.12
     auto cmd_visitor = [&](const auto& cmd) {
             using T = std::decay_t<decltype(cmd)>;
             if constexpr (std::is_same_v<T, Put>) {
+                RECORD_EVENT(TensorCommandEvent, cmd.dest->id, TensorCommandEvent::Put);
                 auto value = cmd.no_cache ? std::make_shared<Tensor>(cmd.value) : Tensor::make(cmd.value);
                 produce_tensor(cmd.dest, std::move(value));
+                RECORD_EVENT(TensorCommandFinishEvent, cmd.dest->id, TensorCommandFinishEvent::Put);
+                sample_on_device(cmd.dest->desc.comp_node, false);
             } else if constexpr (std::is_same_v<T, ApplyOp>) {
                 do_apply_op(cmd);
                 for (size_t i = 0; i < cmd.outputs.size(); ++i) {
@@ -739,7 +798,7 @@ void ChannelImpl::process_one_task(IdentifiedCommand& icmd) {
                         continue;
                     }
                     if (state.options.enable_dtr_auto_drop) {
-                        cmd.outputs[i]->dsu_ptr = std::make_shared<DsuNode>(output->compute_time);
+                        output->dsu_ptr = std::make_shared<DsuNode>(output->compute_time);
                     }
                 }
                 if (state.options.enable_drop && state.options.record_computing_path) {
@@ -765,6 +824,7 @@ void ChannelImpl::process_one_task(IdentifiedCommand& icmd) {
 
                     bool cross_cn = any_of(concat(cmd.inputs, cmd.outputs), is_cross_cn);
                     bool inplace = any_of(cartesian_product(cmd.inputs, cmd.outputs), is_inplace);
+
                     if (!inplace && !cross_cn && !m_dtr.is_bad_op(get_name(*cmd.op))) {
                         TensorInfo::ComputePath::make(cmd.id, cmd.op, cmd.inputs, cmd.outputs);
                         size_t detach_cnt = 0;
@@ -780,7 +840,12 @@ void ChannelImpl::process_one_task(IdentifiedCommand& icmd) {
                     }
                 }
             } else if constexpr (std::is_same_v<T, Del>) {
+                RECORD_EVENT(TensorCommandEvent, cmd.dest->id, TensorCommandEvent::Del);
+                CompNode device = cmd.dest->desc.comp_node;
+                uint64_t tensor_id = cmd.dest->id;
                 free(cmd.dest);
+                RECORD_EVENT(TensorCommandFinishEvent, tensor_id, TensorCommandFinishEvent::Del);
+                sample_on_device(device, false);
             } else if constexpr (std::is_same_v<T, GetValue>) {
                 if (!cmd.dest->ptr && cmd.dest->evict_type != EvictType::NONE) {
                     regenerate(cmd.dest);
@@ -788,50 +853,62 @@ void ChannelImpl::process_one_task(IdentifiedCommand& icmd) {
                 mgb_assert(cmd.dest->ptr, "Invalid tensor ptr!");
                 cmd.dest->ptr->fetch_value();
                 MGB_LOCK_GUARD(m_mutex);
-                cmd.dest->value_fetched = true;
-                if (m_waitee == cmd.dest) {
-                    m_cv.notify_all();
-                }
+                notify_tensor_unsafe(cmd.dest);
             } else if constexpr (std::is_same_v<T, SwapIn>) {
+                RECORD_EVENT(TensorCommandEvent, cmd.dest->id, TensorCommandEvent::SwapIn);
                 produce_tensor(cmd.dest, Tensor::make(cmd.dest->h_value));
+                RECORD_EVENT(TensorCommandFinishEvent, cmd.dest->id, TensorCommandFinishEvent::SwapIn);
+                sample_on_device(cmd.dest->desc.comp_node, false);
             } else if constexpr (std::is_same_v<T, SwapOut>) {
+                RECORD_EVENT(TensorCommandEvent, cmd.dest->id, TensorCommandEvent::SwapOut);
                 cmd.dest->h_value = cmd.dest->ptr->get_value();
                 if (cmd.dest->evict_type == EvictType::NONE) {
-                    release_tensor(cmd.dest);
                     cmd.dest->evict_type = EvictType::SWAP;
+                    cmd.dest->status = TensorInfo::Swapped;
+                    release_tensor(cmd.dest);
                 }
+                RECORD_EVENT(TensorCommandFinishEvent, cmd.dest->id, TensorCommandFinishEvent::SwapOut);
+                sample_on_device(cmd.dest->desc.comp_node, false);
             } else if constexpr (std::is_same_v<T, Drop>) {
+                RECORD_EVENT(TensorCommandEvent, cmd.dest->id, TensorCommandEvent::Drop);
                 do_drop(cmd.dest, true);
+                RECORD_EVENT(TensorCommandFinishEvent, cmd.dest->id, TensorCommandFinishEvent::Drop);
             } else if constexpr (std::is_same_v<T, SetOption>) {
-                state.options.set_option(cmd.key, cmd.value);
+                options.set_option(cmd.key, cmd.value);
             } else if constexpr (std::is_same_v<T, StartProfile>) {
+                RECORD_EVENT(StartProfileEvent);
                 CompNode::sync_all();
-                state.profiler.reset(cmd.profiler);
+                for (auto* info: cmd.capture_tensors) {
+                    RECORD_EVENT(TensorDeclareEvent, info->id, info->name);
+                    if (info->status == TensorInfo::Produced) {
+                        // TODO: handle swap/drop
+                        RECORD_EVENT(TensorProduceEvent, info->id, info->desc.layout, info->desc.comp_node, info->ptr->dev_tensor().raw_ptr());
+                    }
+                }
+                CompNode::foreach([&](CompNode device){
+                    if (Profiler::get_option("sample_rate", 0)) {
+                        sample_on_device(device, true);
+                    }
+                });
+                RECORD_EVENT(StartProfileFinishEvent);
             } else if constexpr (std::is_same_v<T, StopProfile>) {
-                for (auto&& [device, scopes]: state.device_scope_map) {
-                    MGB_MARK_USED_VAR(scopes);
-                    sync_device_scope(device);
+                RECORD_EVENT(StopProfileEvent);
+                for (auto* info: cmd.escape_tensors) {
+                    bool has_value = info->status == TensorInfo::Produced;
+                    if (has_value) {
+                        RECORD_EVENT(TensorReleaseEvent, info->id);
+                    }
+                    RECORD_EVENT(TensorEraseEvent, info->id);
                 }
-                do_finish_command();
-                auto profiler = std::make_unique<InterpreterProfiler>();
-                std::swap(profiler, state.profiler);
-                auto records = profiler->stop();
-                auto worker_tid = get_worker_tid();
-                auto host_map = [worker_tid](std::thread::id tid) {
-                    if (tid == worker_tid) {
-                        return "worker";
-                    } else {
-                        return "unknown";
+                CompNode::foreach([&](CompNode device){
+                    if (Profiler::get_option("sample_rate", 0)) {
+                        sample_on_device(device, true);
                     }
-                };
+                });
+                RECORD_EVENT(StopProfileFinishEvent);
             } else if constexpr (std::is_same_v<T, PushScope>) {
-                state.scopes.push_back(cmd.scope_name);
-                do_finish_command();
                 RECORD_EVENT(ScopeEvent, cmd.scope_name);
             } else if constexpr (std::is_same_v<T, PopScope>) {
-                mgb_assert(state.scopes.back() == cmd.scope_name, "scope name mismatch");
-                state.scopes.pop_back();
-                do_finish_command();
                 RECORD_EVENT(ScopeFinishEvent, cmd.scope_name);
             } else {
                 static_assert(!std::is_same_v<T, T>);
@@ -839,7 +916,7 @@ void ChannelImpl::process_one_task(IdentifiedCommand& icmd) {
     };
     std::visit([&](const auto& cmd){
         using T = std::decay_t<decltype(cmd)>;
-        if (!state.options.catch_worker_execption) {
+        if (!options.catch_worker_execption) {
             cmd_visitor(cmd);
             return;
         }
@@ -855,10 +932,12 @@ void ChannelImpl::process_one_task(IdentifiedCommand& icmd) {
                 cmd.dest->invalid = true;
             }
             m_worker_exc = std::current_exception();
-            m_cv.notify_all();
+            RECORD_EVENT(WorkerExceptionEvent);
+            if (m_waitee) {
+                notify_tensor_unsafe(m_waitee);
+            }
         }
     }, icmd.second);
-    do_finish_command();
 }
 
 void ChannelImpl::check_worker_exc_unsafe() {
@@ -888,17 +967,17 @@ void ChannelImpl::CommandBuffer::flush() {
 void ChannelImpl::CommandBuffer::flush(Handle pos) {
     auto& state = m_owner->get_channel_state();
     for (auto iter = m_commands.begin(); iter != pos; ++iter) {
-        // mgb_log_debug("%s Flushed", to_string(*iter).c_str());
-        IdentifiedCommand icmd{++m_owner->m_last_id, std::move(*iter)};
-        RECORD_EVENT(CommandEnqueueEvent, icmd);
-        m_owner->m_worker.add_task(std::move(icmd));
+        if (Profiler::is_profiling()) {
+            mgb_log_debug("%s Flushed", to_string(*iter).c_str());
+        }
+        m_owner->m_worker.add_task(IdentifiedCommand{Profiler::next_id(), std::move(*iter)});
     }
     m_commands.erase(m_commands.begin(), pos);
 }
 
 auto ChannelImpl::CommandBuffer::flush_pos_for(const Command& cmd) -> Handle {
     auto& state = m_owner->get_channel_state();
-    return std::visit([&, this](const auto& cmd) {
+    return std::visit([this, &state](const auto& cmd) {
         using T = std::decay_t<decltype(cmd)>;
         if constexpr (std::is_same_v<T, ApplyOp>) {
             auto* op_type = cmd.op->dyn_typeinfo();
@@ -986,46 +1065,37 @@ auto ChannelImpl::CommandBuffer::find_produce(TensorInfo* dest, Range range)
     });
 }
 
-void ChannelImpl::start_profile(std::unordered_map<std::string, int> option) {
+void ChannelImpl::start_profile() {
     mgb_assert(check_available(), "Channel already closed");
-    auto& state = get_channel_state();
-    auto profiler_option = InterpreterProfiler::Option::from_dict(option);
-    auto profiler = std::make_unique<InterpreterProfiler>();
-    profiler->set_option(profiler_option);
-    profiler->start(InterpreterProfiler::topic_to_mask(profiler_option.topic));
-    std::swap(profiler, state.profiler);
-    m_buffer.enqueue(StartProfile{state.profiler.get()});
+    auto capture_tensors = collect_valid_tensors();
+    if (capture_tensors.size() > 0) {
+        m_buffer.enqueue(StartProfile{std::move(capture_tensors)});
+    }
 }
 
-void ChannelImpl::stop_profile(std::string basename, std::string format) {
+void ChannelImpl::stop_profile() {
     mgb_assert(check_available(), "Channel already closed");
-    auto& state = get_channel_state();
     m_buffer.flush();
-    auto profiler = std::make_unique<InterpreterProfiler>();
-    std::swap(profiler, state.profiler);
-    profiler.release();
-    m_buffer.enqueue(StopProfile{basename, format});
+    auto escape_tensors = collect_valid_tensors();
+    if (escape_tensors.size() > 0) {
+        m_buffer.enqueue(StopProfile{std::move(escape_tensors)});
+    }
 }
 
 void ChannelImpl::push_scope(std::string name) {
     mgb_assert(check_available(), "Channel already closed");
     auto& state = get_channel_state();
+    state.scopes.push(name);
     RECORD_EVENT(ScopeEvent, name);
-    if (state.profiler->is_profiling()) {
-        state.scopes.push_back(name);
-        m_buffer.enqueue(PushScope{name});
-    }
+    m_buffer.enqueue(PushScope{name});
 }
 
 void ChannelImpl::pop_scope(std::string name) {
     mgb_assert(check_available(), "Channel already closed");
     auto& state = get_channel_state();
+    state.scopes.pop(name);
     RECORD_EVENT(ScopeFinishEvent, name);
-    if (state.profiler->is_profiling()) {
-        mgb_assert((!state.scopes.empty()) && state.scopes.back() == name, "scope name mismatch");
-        state.scopes.pop_back();
-        m_buffer.enqueue(PopScope{name});
-    }
+    m_buffer.enqueue(PopScope{name});
 }
 
 void ChannelImpl::assert_in_channel() {
@@ -1036,6 +1106,19 @@ void ChannelImpl::assert_in_worker() {
     mgb_assert(get_worker_tid() == std::this_thread::get_id(), "this method can only be called in worker thread");
 }
 
+void ChannelImpl::sample_on_device(CompNode device, bool force) {
+    if (!force) {
+        thread_local int last_sample_id = 0;
+        int sample_rate = Profiler::is_profiling() ? Profiler::get_option("sample_rate", 0) : 0;
+        if (!sample_rate || ((++last_sample_id) % sample_rate != 0)) {
+            return;
+        }
+    }
+    RECORD_EVENT(SampleDeviceEvent, device);
+    auto [total, free] = device.get_mem_status_bytes();
+    RECORD_EVENT(SampleDeviceFinishEvent, device, total, free);
+}
+
 void ChannelImpl::DynamicSublinear::pin(const SmallVector<TensorInfo*>& vec) {
     for (auto i : vec) {
         i->pin();
diff --git a/imperative/src/impl/interpreter/interpreter_impl.h b/imperative/src/impl/interpreter/interpreter_impl.h
index b459f54f96c416b3a03df2cf320f0ec8b5c3564b..dec584d147b28d0ea83e9a0879b839497d54bee7 100644
--- a/imperative/src/impl/interpreter/interpreter_impl.h
+++ b/imperative/src/impl/interpreter/interpreter_impl.h
@@ -24,10 +24,10 @@
 #include "megbrain/imperative/profiler.h"
 
 #include "./commands.h"
-#include "./events.h"
 #include "./tensor_info.h"
 #include "./option_manager.h"
-#include "./profiler.h"
+
+#include "../profiler/events.h"
 
 namespace mgb::imperative::interpreter::intl {
 
@@ -37,7 +37,6 @@ struct InterpreterImpl : Interpreter {
     std::unique_ptr<Channel> create_channel() override;
 };
 
-
 struct ChannelImpl : Interpreter::Channel {
     ChannelImpl();
     ~ChannelImpl() override;
@@ -67,19 +66,27 @@ struct ChannelImpl : Interpreter::Channel {
     size_t get_option(std::string name) override;
     void set_option(std::string name, size_t value) override;
 
-    void start_profile(std::unordered_map<std::string, int> option) override;
-    void stop_profile(std::string basename, std::string format) override;
+    void start_profile() override;
+    void stop_profile() override;
 
     void push_scope(std::string) override;
     void pop_scope(std::string) override;
 private:
+    struct WorkQueue;
+    struct State;
+
     TensorInfo* alloc();
+    void init(TensorInfo*, LogicalTensorDesc desc);
     void free(TensorInfo*);
     void real_free(TensorInfo*);
     void recursive_free(TensorInfo*);
     void do_drop(TensorInfo*, bool);
     void detach_users(TensorInfo*);
 
+    TensorInfo* put_impl(const HostTensorND& value, bool no_cache);
+    TensorPtr wait_tensor(TensorInfo* info, profiler::TensorProp prop);
+    void notify_tensor_unsafe(TensorInfo* info);
+
     void process_one_task(IdentifiedCommand&);
 
     void check_worker_exc_unsafe();
@@ -105,24 +112,31 @@ private:
 
     bool check_available();
 
+    void push_scope(std::string, State&);
+    void pop_scope(std::string, State&);
+
     void assert_in_channel();
     void assert_in_worker();
     std::thread::id get_worker_tid();
 
-    void sync_device_scope(CompNode device);
-
     template <typename TCommand>
     void enqueue_command(TCommand&& cmd) {
         m_buffer.enqueue(Command{std::forward<TCommand>(cmd)});
     }
 
+    void sample_on_device(CompNode device, bool force);
+
+    // valid => status != Deleted
+    std::unordered_set<TensorInfo*> collect_valid_tensors();
+
     std::mutex m_mutex;
     std::condition_variable m_cv;
     MemPool<TensorInfo> m_pool;
     std::unordered_set<Handle> m_valid_handle;
     TensorInfo* m_waitee = nullptr;
+    uint64_t m_waitee_id = 0;
     std::exception_ptr m_worker_exc;
-    std::atomic_uint64_t m_last_id = 0;
+    std::function<void(std::string, std::string)> m_profile_dump_callback;
 
     bool m_closed = false;
 
@@ -191,27 +205,98 @@ private:
     //! level 0: both sync.
     int m_async_level = 2;
 
-    struct State {
-        OptionManager options;
-        std::vector<std::string> scopes;
-        std::unique_ptr<InterpreterProfiler> profiler;
+    struct Scope {
+        std::string name;
+        std::unordered_map<std::string, std::unique_ptr<Scope>> children;
+        size_t version = 0;
+        size_t parent_version = 0;
+        size_t tensor_count = 0;
+        Scope* active_child = nullptr;
+        Scope* parent = nullptr;
+
+        Scope* enter(std::string name) {
+            auto& child = children[name];
+            if (!child) {
+                child = std::make_unique<Scope>();
+                child->name = name;
+                child->parent = this;
+            }
+            if (version != child->parent_version) {
+                child->version = 0;
+                child->parent_version = version;
+            } else {
+                child->version++;
+            }
+            child->tensor_count = 0;
+            return active_child = child.get();
+        }
 
-        State() {
-            profiler = std::make_unique<InterpreterProfiler>();
+        Scope* exit(std::string name) {
+            mgb_assert(this->name == name, "scope name mismatch");
+            parent->active_child = nullptr;
+            return parent;
         }
     };
 
-    struct ChannelState: State {};
+    class ScopeManager {
+    private:
+        Scope m_root;
+        Scope* m_current_scope = &m_root;
+    public:
+        class ScopeGuard{
+        private:
+            ScopeManager* m_manager;
+            std::string m_name;
+        public:
+            ScopeGuard(ScopeManager* manager, std::string name): m_manager{manager}, m_name{name} {
+                m_manager->push(m_name);
+            }
+            ~ScopeGuard() {
+                m_manager->pop(m_name);
+            }
+        };
+        void push(std::string name) {
+            m_current_scope = m_current_scope->enter(name);
+        }
+        void pop(std::string name) {
+            m_current_scope = m_current_scope->exit(name);
+        }
+        std::string next_tensor_name() {
+            std::string builder;
+            Scope* scope = &m_root;
+            while (true) {
+                builder.append(scope->name);
+                if (scope->version != 0) {
+                    builder.append(ssprintf("(%ld)", scope->version));
+                }
+                if (scope != &m_root) {
+                    builder.append(".");
+                }
+                if (scope->active_child == nullptr) {
+                    builder.append(ssprintf(":%%%ld", scope->tensor_count++));
+                    break;
+                } else {
+                    scope = scope->active_child;
+                }
+            }
+            return builder;
+        }
+    };
 
-    struct WorkerState: State {
+    struct State {
         std::thread::id tid;
-        CompNode::UnorderedMap<std::vector<std::string>> device_scope_map;
+        OptionManager options;
     };
 
+    struct ChannelState: State {
+        ScopeManager scopes;
+    };
+
+    struct WorkerState: State {};
+
     ChannelState m_channel_state;
     WorkerState m_worker_state;
 
-
     /*!
      * \brief A framework of dynamic sublienar memory optimization
      *
@@ -327,7 +412,6 @@ private:
     // assert thread id when call get_xxx_state to avoid misuse
     ChannelState& get_channel_state();
     WorkerState& get_worker_state();
-
 };
 
 } // namespace mgb::imperative::interpreter::intl
diff --git a/imperative/src/impl/interpreter/profiler.h b/imperative/src/impl/interpreter/profiler.h
deleted file mode 100644
index 538a3540fc91e53e6328c400ad4db4b3876ff01a..0000000000000000000000000000000000000000
--- a/imperative/src/impl/interpreter/profiler.h
+++ /dev/null
@@ -1,93 +0,0 @@
-/**
- * \file imperative/src/impl/interpreter/profiler.h
- * MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
- *
- * Copyright (c) 2014-2020 Megvii Inc. All rights reserved.
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the License is distributed on an
- * "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- */
-
-#pragma once
-
-#include "megbrain/imperative/profiler.h"
-
-#include "./commands.h"
-#include "./events.h"
-#include "./option_manager.h"
-
-namespace mgb::imperative::interpreter::intl {
-
-class InterpreterProfiler: public Profiler<
-        CommandEnqueueEvent, CommandExecuteEvent, CommandFinishEvent,
-        OpExecuteEvent, OpExecuteFinishEvent,
-        KernelExecuteEvent, KernelExecuteFinishEvent,
-        TensorDeclareEvent, TensorProduceEvent, TensorEraseEvent,
-        TensorGetPropEvent, TensorWaitPropEvent, TensorNotifyPropEvent, TensorWaitPropFinishEvent,
-        SyncEvent, SyncFinishEvent,
-        ScopeEvent, ScopeFinishEvent,
-        DeviceScopeEvent, DeviceScopeFinishEvent> {
-
-public:
-    enum Topic {
-        Command         = 0b000001,
-        Operator        = 0b000010,
-        TensorLifetime  = 0b000100,
-        TensorProp      = 0b001000,
-        Sync            = 0b010000,
-        Scope           = 0b100000,
-    };
-
-    struct Option {
-        Topic topic;
-        bool align_time;
-        bool show_operator_name;
-
-        static Option from_dict(std::unordered_map<std::string, int> dict) {
-            Option option;
-            option.topic = Topic(dict.at("topic"));
-            option.align_time = bool(dict.at("align_time"));
-            option.show_operator_name = bool(dict.at("show_operator_name"));
-            return option;
-        }
-    };
-
-    Option get_option() const {
-        return m_option;
-    }
-
-    void set_option(const Option& option) {
-        m_option = option;
-    }
-
-    static Mask topic_to_mask(Topic topic) {
-        Mask result;
-        if (topic & Command) {
-            result |= mask_of<CommandEnqueueEvent, CommandExecuteEvent, CommandFinishEvent>();
-        }
-        if (topic & Operator) {
-            result |= mask_of<OpExecuteEvent, OpExecuteFinishEvent>();
-            result |= mask_of<KernelExecuteEvent, KernelExecuteFinishEvent>();
-        }
-        if (topic & TensorLifetime) {
-            result |= mask_of<TensorDeclareEvent, TensorProduceEvent, TensorEraseEvent>();
-        }
-        if (topic & TensorProp) {
-            result |= mask_of<TensorGetPropEvent, TensorWaitPropEvent, TensorNotifyPropEvent, TensorWaitPropFinishEvent>();
-        }
-        if (topic & Sync) {
-            result |= mask_of<SyncEvent, SyncFinishEvent>();
-        }
-        if (topic & Scope) {
-            result |= mask_of<ScopeEvent, ScopeFinishEvent>();
-            result |= mask_of<DeviceScopeEvent, DeviceScopeFinishEvent>();
-        }
-        return result;
-    }
-
-private:
-    Option m_option;
-};
-
-}
diff --git a/imperative/src/impl/interpreter/tensor_info.h b/imperative/src/impl/interpreter/tensor_info.h
index 11e98a15df38969a71b332b6b87d9289b12bf1ae..5a3067ca056e55a86423d0b959ee5e9147850101 100644
--- a/imperative/src/impl/interpreter/tensor_info.h
+++ b/imperative/src/impl/interpreter/tensor_info.h
@@ -27,19 +27,19 @@ enum EvictType {
 
 /*!
  * \brief an identifier to specify a component of evicted tensors
- * 
+ *
  * Each component tracks the sum of the compute costs of its elements, with the
  * union of two components having the sum of each constituent cost.
  */
 struct DsuNode {
     DsuNode(double _t): t(_t) {}
-    
+
     std::shared_ptr<DsuNode> parent;
 
     bool is_root() {
         return !bool(parent);
     }
-    
+
     double t;
 };
 
@@ -47,25 +47,33 @@ struct TensorInfo;
 using TensorInfoPtr = std::shared_ptr<TensorInfo>;
 
 struct TensorInfo {
-    enum Prop {
-        Device, Shape, DType, DevValue, HostValue
+    enum Status {
+        InvalidStatus, Allocated, Produced, Swapped, Dropped, Deleted,
     };
 
-    uint64_t id;
+    uint64_t id = -1;
+    std::string name;
+    // Most attrs of TensorInfo, except `ptr` and `h_value`,
+    // were visited read and written in main thread.
+    // Lock interpreter when visiting `ptr`.
     TensorPtr ptr;
     LogicalTensorDesc desc;
 
     double compute_time;
     size_t memory;
     double last_used_time;
-    
-    // FIXME: broken by drop
-    bool value_fetched = false;
+
     bool invalid = false;
     bool allow_delete = false;
 
     EvictType evict_type = NONE;
 
+    // Status should be only modified in worker thread
+    Status status = InvalidStatus;
+
+    // Used by HostCompute and Memory Swap.
+    // HostCompute and Swap does not happen in one thread.
+    // Maybe a barrier is needed.
     HostTensorND h_value;
 
     // reserved for auto drop
@@ -74,6 +82,10 @@ struct TensorInfo {
     size_t ref_cnt = 0;
     std::shared_ptr<DsuNode> dsu_ptr;
 
+    // Not reference count, inc when used as input
+    size_t ptr_use_count = 0;
+
+    // Used by `Drop` action
     struct ComputePath {
         uint64_t id;
         std::shared_ptr<OpDef> op;
@@ -111,7 +123,7 @@ struct TensorInfo {
             return path;
         }
     }* producer = nullptr;
-  
+
     double eval_func(double cost, double free_mem, double cur_time,
                      double param_cost, double param_mem, double param_time, double param_recompute_times) {
         return pow(cost + 1e-3, param_cost) * pow(param_recompute_times, (double)recompute_times)
@@ -126,20 +138,24 @@ struct TensorInfo {
         --pinned;
     }
 
-    void detach_producer() {
+    // returns true if producer is deleted
+    bool detach_producer() {
         if (!producer) {
-            return;
+            return false;
         }
         auto output = std::find(producer->outputs.begin(), producer->outputs.end(), this);
         mgb_assert(output != producer->outputs.end());
         *output = nullptr;
+        bool deleted = false;
         if (producer->ref_cnt() == 0) {
             for (auto* input: producer->unique_inputs) {
                 input->users.erase(std::find(input->users.begin(), input->users.end(), producer));
             }
             delete producer;
+            deleted = true;
         }
         producer = nullptr;
+        return deleted;
     }
 
     bool size_exceeds_thd(size_t thd) {
@@ -150,26 +166,4 @@ struct TensorInfo {
 };
 }
 
-template <>
-struct ToStringTrait<interpreter::intl::TensorInfo::Prop>{
-    using TensorInfo = interpreter::intl::TensorInfo;
-
-    std::string operator()(TensorInfo::Prop prop) const {
-        switch(prop) {
-        case TensorInfo::DType:
-            return "dtype";
-        case TensorInfo::DevValue:
-            return "dev_value";
-        case TensorInfo::Device:
-            return "device";
-        case TensorInfo::HostValue:
-            return "host_value";
-        case TensorInfo::Shape:
-            return "shape";
-        default:
-            return "unknown";
-        }
-    }
-};
-
 }
diff --git a/imperative/src/impl/profiler.cpp b/imperative/src/impl/profiler.cpp
index 7aeb5674f20485033fe0639a1e153743beee39a1..2c9f6c275bf154db8347717c03554397e7c7e32d 100644
--- a/imperative/src/impl/profiler.cpp
+++ b/imperative/src/impl/profiler.cpp
@@ -22,47 +22,58 @@
 #include "./event_pool.h"
 #include "./op_trait.h"
 
+#include "./profiler/formats.h"
+
 namespace mgb {
 namespace imperative {
 
-namespace {
-
-DeviceTimer::SharedEvent alloc_recorded_event(CompNode device) {
-    auto event = EventPool::with_timer().alloc_shared(device);
-    event->record();
-    return event;
+uint64_t Timer::get_nsecs() {
+    using namespace std::chrono;
+    auto finish = steady_clock::now();
+    auto duration = duration_cast<nanoseconds>(finish - m_start);
+    return duration.count();
 }
 
-}  // namespace
-
-DeviceTimer::SharedEvent DeviceTimer::get_device_time(CompNode device) {
-    return alloc_recorded_event(device);
+uint64_t Timer::get_started_at() {
+    return m_started_at;
 }
 
-SmallVector<DeviceTimer::SharedEvent> DeviceTimer::get_all(SmallVector<CompNode> device_list) {
-    SmallVector<DeviceTimer::SharedEvent> results;
-    for (auto&& device: device_list) {
-        results.push_back(alloc_recorded_event(device));
-    }
-    return results;
+void Timer::reset() {
+    using namespace std::chrono;
+    m_start = steady_clock::now();
+    auto now_ns = duration_cast<nanoseconds>(std::chrono::system_clock::now().time_since_epoch());
+    m_started_at = now_ns.count();
 }
 
-double HostTimer::get_msecs() {
-    using namespace std::chrono;
-    auto finish = steady_clock::now();
-    auto duration = duration_cast<microseconds>(finish - m_start);
-    return (double)duration.count() / 1e3;
+std::shared_ptr<CompNode::Event> Timer::record_event(CompNode device) {
+    auto event = EventPool::with_timer().alloc_shared(device);
+    event->record();
+    return event;
 }
 
-double HostTimer::get_started_at() {
-    return m_started_at;
+Profiler::options_t Profiler::sm_profile_options;
+std::mutex Profiler::sm_mutex;
+std::unordered_map<std::thread::id, Profiler*> Profiler::sm_profilers;
+Timer Profiler::sm_timer;
+std::atomic_uint64_t Profiler::sm_last_id = 0;
+bool Profiler::sm_profiling = false;
+thread_local std::unique_ptr<Profiler> Profiler::tm_profiler = std::make_unique<Profiler>();
+std::atomic_size_t Profiler::sm_preferred_capacity;
+
+auto Profiler::get_thread_dict() -> thread_dict_t {
+    MGB_LOCK_GUARD(sm_mutex);
+    thread_dict_t thread_dict;
+    for (auto&& [tid, profiler]: sm_profilers) {
+        thread_dict[tid] = profiler->m_thread_name;
+    }
+    return thread_dict;
 }
 
-void HostTimer::reset() {
-    using namespace std::chrono;
-    m_start = steady_clock::now();
-    auto now_us = duration_cast<microseconds>(std::chrono::system_clock::now().time_since_epoch());
-    m_started_at = (double)(now_us.count()) / 1e3;
+void Profiler::dump_profile(std::string basename, std::string format, results_t results, options_t options) {
+    auto thread_dict = get_thread_dict();
+    {
+        mgb_log_error("unsupported profiling format %s", format.c_str());
+    }
 }
 
 }  // namespace imperative
diff --git a/imperative/src/impl/profiler/chrome_timeline.cpp b/imperative/src/impl/profiler/chrome_timeline.cpp
deleted file mode 100644
index 956ae90b095a6f7caaa754382a58dfa7c5008cf0..0000000000000000000000000000000000000000
--- a/imperative/src/impl/profiler/chrome_timeline.cpp
+++ /dev/null
@@ -1,145 +0,0 @@
-#include <string>
-#include <memory>
-#include "megbrain/utils/json.h"
-
-namespace mgb {
-namespace imperative {
-
-class ChromeTraceEvent {
-public:
-    ChromeTraceEvent& name(std::string name) {
-        m_name = std::move(name);
-        return *this;
-    }
-    ChromeTraceEvent& tid(uint64_t tid) {
-        m_tid = std::move(tid);
-        return *this;
-    }
-    ChromeTraceEvent& cat(std::string cat) {
-        m_cat = std::move(cat);
-        return *this;
-    }
-    ChromeTraceEvent& pid(uint64_t pid) {
-        m_pid = pid;
-        return *this;
-    }
-    ChromeTraceEvent& id(uint64_t id) {
-        m_id = id;
-        return *this;
-    }
-    ChromeTraceEvent& idx(uint64_t idx) {
-        m_idx = idx;
-        return *this;
-    }
-    ChromeTraceEvent& ts(double ts) {
-        m_ts = ts;
-        return *this;
-    }
-    ChromeTraceEvent& dur(double dur) {
-        m_dur = dur;
-        return *this;
-    }
-    ChromeTraceEvent& ph(char ph) {
-        m_ph = ph;
-        return *this;
-    }
-    ChromeTraceEvent& bp(char bp) {
-        m_bp = bp;
-        return *this;
-    }
-    ChromeTraceEvent& args(std::shared_ptr<json::Object> args) {
-        m_args = std::move(args);
-        return *this;
-    }
-    ChromeTraceEvent& arg(std::string key, std::string value) {
-        if (!m_args) {
-            m_args = json::Object::make();
-        }
-        (*m_args)[key] = json::String::make(value);
-        return *this;
-    }
-    ChromeTraceEvent& arg(std::string key, double value) {
-        if (!m_args) {
-            m_args = json::Object::make();
-        }
-        (*m_args)[key] = json::Number::make(value);
-        return *this;
-    }
-    ChromeTraceEvent& arg(std::string key, std::shared_ptr<json::Value> value) {
-        if (!m_args) {
-            m_args = json::Object::make();
-        }
-        (*m_args)[key] = value;
-        return *this;
-    }
-
-    std::shared_ptr<json::Object> to_json() const {
-        auto result = json::Object::make();
-        auto prop_str = [&](auto key, auto value) {
-            if (value.empty()) {
-                return;
-            }
-            (*result)[key] = json::String::make(value);
-        };
-        auto prop_num = [&](auto key, auto value) {
-            if (!value) {
-                return;
-            }
-            (*result)[key] = json::Number::make(value.value());
-        };
-        auto prop_char = [&](auto key, auto value) {
-            if (!value) {
-                return;
-            }
-            (*result)[key] = json::String::make(std::string{} + value.value());
-        };
-        prop_str("name", m_name);
-        prop_num("tid", m_tid);
-        prop_str("cat", m_cat);
-        prop_num("pid", m_pid);
-        prop_num("id", m_id);
-        prop_num("idx", m_idx);
-        prop_num("ts", m_ts);
-        prop_num("dur", m_dur);
-        prop_char("ph", m_ph);
-        prop_char("bp", m_bp);
-        if (m_args) {
-            (*result)["args"] = m_args;
-        }
-        return result;
-    }
-private:
-    std::string m_name;
-    std::string m_cat;
-
-    std::optional<uint64_t> m_tid;
-    std::optional<uint64_t> m_pid;
-    std::optional<uint64_t> m_id;
-    std::optional<uint64_t> m_idx;
-    std::optional<double> m_ts;
-    std::optional<double> m_dur;
-    std::optional<char> m_ph;
-    std::optional<char> m_bp;
-    std::shared_ptr<json::Object> m_args;
-};
-
-class ChromeTraceEventList {
-public:
-    ChromeTraceEvent& new_event() {
-        m_content.emplace_back();
-        return m_content.back();
-    }
-
-    std::shared_ptr<json::Array> to_json() const {
-        auto result = json::Array::make();
-        for (auto&& event: m_content) {
-            result->add(event.to_json());
-        }
-        return result;
-    }
-private:
-    std::vector<ChromeTraceEvent> m_content;
-};
-
-}  // namespace imperative
-}  // namespace mgb
diff --git a/imperative/src/impl/profiler/events.h b/imperative/src/impl/profiler/events.h
new file mode 100644
index 0000000000000000000000000000000000000000..c51ffe2fa48801dce9a1e27194a679358cdc0546
--- /dev/null
+++ b/imperative/src/impl/profiler/events.h
@@ -0,0 +1,186 @@
+/**
+ * \file imperative/src/impl/interpreter/events.h
+ * MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
+ *
+ * Copyright (c) 2014-2020 Megvii Inc. All rights reserved.
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ */
+
+#pragma once
+
+#include "megbrain/utils/small_vector.h"
+
+#include "../op_trait.h"
+
+namespace mgb::imperative::profiler {
+
+enum class TensorProp {
+    InvalidProp, Device, Shape, DType, DevValue, HostValue,
+};
+
+using OpParams = std::unordered_map<std::string, std::string>;
+
+}
+
+namespace mgb::imperative {
+
+template <>
+struct ToStringTrait<profiler::TensorProp>{
+    using TensorProp = profiler::TensorProp;
+    std::string operator()(TensorProp prop) const {
+        switch(prop) {
+        case TensorProp::DType:
+            return "dtype";
+        case TensorProp::DevValue:
+            return "dev_value";
+        case TensorProp::Device:
+            return "device";
+        case TensorProp::HostValue:
+            return "host_value";
+        case TensorProp::Shape:
+            return "shape";
+        default:
+            return "unknown";
+        }
+    }
+};
+
+}
+
+namespace mgb::imperative::profiler {
+
+#define DEF_EVENT(X, ...) struct X##Event __VA_ARGS__;
+#define DEF_DUR_EVENT(X, ...) struct X##Event __VA_ARGS__; struct X##FinishEvent __VA_ARGS__;
+
+DEF_EVENT(OpDispatch, {
+    uint64_t op_id;
+    std::string op_name;
+    std::function<OpParams()> op_params;
+    SmallVector<uint64_t> inputs;
+    SmallVector<uint64_t> outputs;
+});
+
+DEF_DUR_EVENT(OpInput, {
+    uint64_t tensor_id;
+    TensorShape shape;
+});
+
+DEF_DUR_EVENT(OpDel, {
+    uint64_t tensor_id;
+    TensorShape shape;
+});
+
+DEF_DUR_EVENT(OpOutput, {
+    uint64_t tensor_id;
+    TensorShape shape;
+});
+
+DEF_DUR_EVENT(OpExecute, {
+    uint64_t op_id;
+});
+
+DEF_DUR_EVENT(OpPostExecute, {
+    uint64_t op_id;
+});
+
+DEF_DUR_EVENT(KernelExecute, {
+    uint64_t op_id;
+    uint64_t kernel_id;
+    std::shared_ptr<CompNode::Event> event;
+});
+
+DEF_EVENT(TensorDeclare, {
+    uint64_t tensor_id;
+    std::string name;
+});
+
+DEF_EVENT(TensorProduce, {
+    uint64_t tensor_id;
+    TensorLayout layout;
+    CompNode device;
+    void* ptr;
+});
+
+DEF_EVENT(TensorUsage, {
+    uint64_t tensor_id;
+});
+
+DEF_EVENT(TensorRelease, {
+    uint64_t tensor_id;
+});
+
+DEF_EVENT(TensorErase, {
+    uint64_t tensor_id;
+    size_t use_count;
+});
+
+DEF_EVENT(TensorGetProp, {
+    uint64_t tensor_id;
+    TensorProp prop;
+});
+
+DEF_EVENT(TensorNotifyProp, {
+    uint64_t tensor_id;
+    uint64_t wait_id;
+    TensorProp prop;
+});
+
+DEF_EVENT(TensorWaitProp, {
+    uint64_t tensor_id;
+    uint64_t wait_id;
+    TensorProp prop;
+});
+
+DEF_EVENT(TensorWaitPropFinish, {
+    uint64_t tensor_id;
+    uint64_t wait_id;
+    TensorProp prop;
+    bool notified;
+});
+
+DEF_DUR_EVENT(SampleDevice, {
+    CompNode device;
+    size_t total_memory;
+    size_t free_memory;
+});
+
+DEF_EVENT(WorkerException, {});
+
+DEF_EVENT(ShapeInfer, {
+    bool success;
+});
+
+DEF_DUR_EVENT(Scope, {
+    std::string name;
+});
+
+DEF_DUR_EVENT(DeviceScope, {
+    std::string name;
+    std::shared_ptr<CompNode::Event> event;
+});
+
+DEF_DUR_EVENT(Sync, {});
+
+DEF_DUR_EVENT(StartProfile, {
+    size_t capture_count;
+});
+
+DEF_DUR_EVENT(StopProfile, {
+    size_t escape_count;
+});
+
+DEF_DUR_EVENT(TensorCommand, {
+    enum Kind {
+        Put, Del, SwapIn, SwapOut, Drop, ReGen, RecFree, GetValue
+    };
+    uint64_t tensor_id;
+    Kind kind;
+});
+
+#undef DEF_EVENT
+#undef DEF_DUR_EVENT
+
+}
diff --git a/imperative/src/impl/interpreter/profiler.cpp b/imperative/src/impl/profiler/formats.h
similarity index 50%
rename from imperative/src/impl/interpreter/profiler.cpp
rename to imperative/src/impl/profiler/formats.h
index ebf8cbc9448e3456183091a75604e515f4ee7bea..05bbda7bf54864f80caffd4a169c52092c527dca 100644
--- a/imperative/src/impl/interpreter/profiler.cpp
+++ b/imperative/src/impl/profiler/formats.h
@@ -1,5 +1,5 @@
 /**
- * \file imperative/src/impl/interpreter/profiler.cpp
+ * \file imperative/src/impl/interpreter/profiler.h
  * MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
  *
  * Copyright (c) 2014-2020 Megvii Inc. All rights reserved.
@@ -9,22 +9,12 @@
  * "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  */
 
-#include "./profiler.h"
+#pragma once
 
-#include <sstream>
-#include <cinttypes>
+#include <unordered_set>
 
-#if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))
-#include <unistd.h>
-#elif defined(_WIN32)
-#include <process.h>
-#else
-#error Unsupported platform
-#endif
-
-#include "../op_trait.h"
-
-namespace mgb::imperative::interpreter::intl {
+#include "megbrain/imperative/profiler.h"
 
+namespace mgb::imperative::profiler {
 
 }
diff --git a/imperative/src/impl/profiler/states.h b/imperative/src/impl/profiler/states.h
index ed3feb6c76168650e5688df8af32652e1b6c5fa2..bfdc2284020410b91f2d1a5fda94a3a34e15123b 100644
--- a/imperative/src/impl/profiler/states.h
+++ b/imperative/src/impl/profiler/states.h
@@ -6,6 +6,8 @@
 
 #include "megbrain/tensor.h"
 
+#include "./events.h"
+
 namespace mgb::imperative::profiler {
 
 struct ProfileDeviceState {
@@ -53,6 +55,7 @@ struct ProfileStaticsState {
 struct ProfileOperatorState {
     uint64_t id;
     std::string name;
+    OpParams params;
     SmallVector<uint64_t> inputs;
     SmallVector<uint64_t> outputs;
     CompNode device;
diff --git a/imperative/src/include/megbrain/imperative/interpreter.h b/imperative/src/include/megbrain/imperative/interpreter.h
index d9de1308560515bc4d0163e3cb68cfd044af5236..a4f29ff4f6fb401774baa0e9f36d5425ee7d8d6a 100644
--- a/imperative/src/include/megbrain/imperative/interpreter.h
+++ b/imperative/src/include/megbrain/imperative/interpreter.h
@@ -47,8 +47,8 @@ struct Interpreter {
         virtual size_t get_option(std::string name) = 0;
         virtual void set_option(std::string name, size_t value) = 0;
 
-        virtual void start_profile(std::unordered_map<std::string, int> option) = 0;
-        virtual void stop_profile(std::string basename, std::string format) = 0;
+        virtual void start_profile() = 0;
+        virtual void stop_profile() = 0;
 
         virtual void push_scope(std::string name) = 0;
         virtual void pop_scope(std::string name) = 0;
diff --git a/imperative/src/include/megbrain/imperative/profiler.h b/imperative/src/include/megbrain/imperative/profiler.h
index 9d2f516586bdd4b1fc0fcfb1b14469f407bcc828..64211da5f11f7121d060e12624968807c67883d5 100644
--- a/imperative/src/include/megbrain/imperative/profiler.h
+++ b/imperative/src/include/megbrain/imperative/profiler.h
@@ -17,6 +17,9 @@
 #include <fstream>
 #include <chrono>
 #include <bitset>
+#include <deque>
+#include <any>
+#include <typeindex>
 
 #include "megbrain/comp_node.h"
 #include "megbrain/graph/event.h"
@@ -29,165 +32,188 @@
 namespace mgb {
 namespace imperative {
 
-class DeviceTimer {
-public:
-    using SharedEvent = std::shared_ptr<CompNode::Event>;
-    DeviceTimer() = default;
-    SharedEvent get_device_time(CompNode device);
-    SmallVector<SharedEvent> get_all(SmallVector<CompNode> device_list);
-};
-
-class HostTimer {
+class Timer {
 public:
     void reset();
-    double get_msecs();
-    double get_started_at();
+    uint64_t get_nsecs();
+    uint64_t get_started_at();
+    static std::shared_ptr<CompNode::Event> record_event(CompNode device);
 private:
     decltype(std::chrono::steady_clock::now()) m_start;
-    double m_started_at;
+    uint64_t m_started_at;
 };
 
 
-class ProfilerBase {
+class Profiler {
 public:
-    using Host = std::thread::id;
-    using Device = CompNode;
-
-    struct HostInstant {
-        Host tid;
-        double time;
-
-        void wait() const {}
+    struct Record {
+        uint64_t id;
+        uint64_t time; //in ns
+        std::any data;
     };
-
-    struct DeviceInstant {
-        double before;
-        std::shared_ptr<CompNode::Event> event;
-        double after;
-
-        void wait() const {
-            event->host_wait();
-        }
+    enum Status: uint8_t {
+        Running = 0,
+        Recording = 1,
+        Collecting = 2,
     };
+    using ProfileCollector = std::function<void(std::thread::id, Record)>;
+    using option_t = uint64_t;
+    using options_t = std::unordered_map<std::string, option_t>;
+    using result_t = std::pair<std::thread::id, Record>;
+    using results_t = std::vector<result_t>;
+    using thread_dict_t = std::unordered_map<std::thread::id, std::string>;
+private:
+    std::thread::id m_thread_id;
+    std::vector<Record> m_records;
+    std::atomic<Status> m_status = Running;
+    uint64_t m_last_time = 0;
+    std::string m_thread_name;
+
+    static options_t sm_profile_options;
+    static std::mutex sm_mutex;
+    static std::unordered_map<std::thread::id, Profiler*> sm_profilers;
+    static Timer sm_timer;
+    static std::atomic_uint64_t sm_last_id;
+    static std::atomic_size_t sm_preferred_capacity;
+    static bool sm_profiling;
+    static constexpr bool sm_debug = false;
+    thread_local static std::unique_ptr<Profiler> tm_profiler;
+public:
+    Profiler() {
+        m_thread_id = std::this_thread::get_id();
+        MGB_LOCK_GUARD(sm_mutex);
+        if (sm_profilers.size() == 0) {
+            reset();
+        }
+        mgb_assert(sm_profilers.count(m_thread_id) == 0);
+        sm_profilers[m_thread_id] = this;
+    }
+    ~Profiler() {
+        MGB_LOCK_GUARD(sm_mutex);
+        mgb_assert(sm_profilers.count(m_thread_id) == 1);
+        sm_profilers.erase(m_thread_id);
+    }
+public:
+    static Profiler& get_instance() {
+        return *tm_profiler;
+    }
 
-    using Instant = std::variant<HostInstant, DeviceInstant>;
+    static void reset() {
+        mgb_assert(sm_profilers.size() == 0, "profiler already running");
+        sm_timer.reset();
+    }
 
-    template <typename TEvent>
-    struct EventRecord {
-        Instant instant;
-        TEvent data;
+    static uint64_t next_id() {
+        return sm_last_id++;
+    }
 
-        const HostInstant& host() const {
-            return std::get<HostInstant>(instant);
+    template <typename T, typename... TArgs>
+    static uint64_t record(TArgs&&... args) {
+        auto& profiler = get_instance();
+        auto last_time = profiler.m_last_time;
+        if constexpr (sm_debug) {
+            Status expected = Running;
+            mgb_assert(profiler.m_status.compare_exchange_strong(expected, Recording));
         }
-
-        const DeviceInstant& device() const {
-            return std::get<DeviceInstant>(instant);
+        uint64_t id = next_id();
+        uint64_t time = sm_timer.get_nsecs();
+        time = std::max(time, last_time + 2000);
+        profiler.m_last_time = time;
+        profiler.m_records.push_back({id, time, T{std::forward<TArgs>(args)...}});
+        if constexpr (sm_debug) {
+            Status expected = Recording;
+            mgb_assert(profiler.m_status.compare_exchange_strong(expected, Running));
         }
+        return id;
+    }
 
-        void wait() const {
-            std::visit([&](const auto& instant){ instant.wait(); }, instant);
+    static results_t collect() {
+        MGB_LOCK_GUARD(sm_mutex);
+        if constexpr (sm_debug) {
+            for (auto&& [tid, profiler]: sm_profilers) {
+                Status expected = Running;
+                mgb_assert(profiler->m_status.compare_exchange_strong(expected, Collecting));
+            }
         }
-    };
-protected:
-    HostInstant record_host() {
-        return {std::this_thread::get_id(), m_host_timer.get_msecs()};
+        std::vector<std::pair<std::thread::id, Record>> profile_data;
+        for (auto&& [tid, profiler]: sm_profilers) {
+            sm_preferred_capacity = std::max(sm_preferred_capacity.load(), profiler->m_records.size());
+            for (auto& record: profiler->m_records) {
+                profile_data.push_back({tid, std::move(record)});
+            }
+            profiler->m_records.clear();
+            profiler->m_records.reserve(sm_preferred_capacity);
+        }
+        std::sort(profile_data.begin(), profile_data.end(), [](auto& lhs, auto& rhs){
+            return lhs.second.id < rhs.second.id;
+        });
+        if constexpr (sm_debug) {
+            for (auto&& [tid, profiler]: sm_profilers) {
+                Status expected = Collecting;
+                mgb_assert(profiler->m_status.compare_exchange_strong(expected, Running));
+            }
+        }
+        return profile_data;
     }
-    DeviceInstant record_device(Device device) {
-        auto before = m_host_timer.get_msecs();
-        auto event = m_device_timer.get_device_time(device);
-        auto after = m_host_timer.get_msecs();
-        return {before, event, after};
+
+    static option_t get_option(std::string key, option_t default_val) {
+        if (!sm_profile_options.count(key)) {
+            return default_val;
+        }
+        return sm_profile_options.at(key);
     }
-protected:
-    std::atomic_int64_t m_last_id = 0;
-    HostTimer m_host_timer;
-    DeviceTimer m_device_timer;
-    Spinlock m_lock;
-};
 
+    static void load_options(options_t options) {
+        sm_profile_options = std::move(options);
+    }
 
-template <typename... TEvents>
-class Profiler: public ProfilerBase {
-public:
-    using Record = std::variant<EventRecord<TEvents>...>;
-    using Mask = std::bitset<sizeof...(TEvents)>;
+    static options_t get_options() {
+        return sm_profile_options;
+    }
 
-    struct Data {
-        std::vector<Record> records;
-        double started_at;
-    };
+    static bool is_profiling() {
+        return sm_profiling;
+    }
 
-    template <typename TEvent, size_t index = 0>
-    static constexpr size_t index_of() {
-        if constexpr (index == std::variant_size_v<Record>) {
-            return index;
-        } else if constexpr (std::is_same_v<EventRecord<TEvent>, std::variant_alternative_t<index, Record>>) {
-            return index;
-        } else {
-            return index_of<TEvent, index+1>();
-        }
-    };
+    static void start_profile() {
+        mgb_assert(!sm_profiling);
+        sm_profiling = true;
+    }
 
-    template <typename... TEvents2>
-    static Mask mask_of() {
-        return Mask{} | (Mask{}.set(index_of<TEvents2>()) |...);
+    static void stop_profile() {
+        mgb_assert(sm_profiling);
+        sm_profiling = false;
     }
 
-    enum Status {
-        NotStarted, Profiling, Stopped
-    };
+    static thread_dict_t get_thread_dict();
+
+    static void dump_profile(std::string basename, std::string format, results_t results, options_t options);
+};
+
+
+class ProfileDataCollector {
 public:
-    template <typename TEvent, typename... TArgs>
-    void record_host(TArgs&&... args) {
-        MGB_LOCK_GUARD(m_lock);
-        if (!m_event_mask.test(index_of<TEvent>())) {
-            return;
-        }
-        mgb_assert(m_status != Stopped, "record after stop");
-        auto instant = HostInstant{std::this_thread::get_id(), m_host_timer.get_msecs()};
-        m_record_list.emplace_back(EventRecord<TEvent>{std::move(instant), {std::forward<TArgs>(args)...}});
+    template <typename T>
+    using SubCollector = std::function<void(uint64_t, std::thread::id, uint64_t, T)>;
+private:
+    std::unordered_map<std::type_index, SubCollector<std::any>> m_collectors;
+public:
+    template <typename T>
+    ProfileDataCollector& handle(SubCollector<T> collector) {
+        auto erased = [collector](uint64_t id, std::thread::id tid, uint64_t time, std::any data){
+            collector(id, tid, time, std::any_cast<T>(std::move(data)));
+        };
+        m_collectors[typeid(T)] = erased;
+        return *this;
     }
-    template <typename TEvent, typename... TArgs>
-    void record_device(Device device, TArgs&&... args) {
-        MGB_LOCK_GUARD(m_lock);
-        if (!m_event_mask.test(index_of<TEvent>())) {
+    void operator()(uint64_t id, std::thread::id tid, uint64_t time, std::any event) {
+        std::type_index type = event.type();
+        if (m_collectors.count(type) == 0) {
             return;
         }
-        mgb_assert(m_status != Stopped, "record after stop");
-        auto before = m_host_timer.get_msecs();
-        auto event = m_device_timer.get_device_time(device);
-        auto after = m_host_timer.get_msecs();
-        auto instant = DeviceInstant{before, event, after};
-        m_record_list.emplace_back(EventRecord<TEvent>{std::move(instant), {std::forward<TArgs>(args)...}});
-    }
-    // unsafe
-    bool is_profiling() {
-        return m_status == Profiling;
-    }
-    void start(Mask mask) {
-        MGB_LOCK_GUARD(m_lock);
-        mgb_assert(m_status == NotStarted, "profiler already started");
-        m_status = Profiling;
-        m_event_mask = mask;
-        m_host_timer.reset();
-    }
-    Data stop() {
-        MGB_LOCK_GUARD(m_lock);
-        mgb_assert(m_status == Profiling, "profiler not active");
-        m_status = Stopped;
-        for (auto&& record: m_record_list) {
-            std::visit([&](const auto& record){
-                record.wait();
-            }, record);
-        }
-        auto records = std::move(m_record_list);
-        return { records, m_host_timer.get_started_at() };
+        auto& handler = m_collectors.at(type);
+        handler(id, tid, time, std::move(event));
     }
-protected:
-    std::vector<Record> m_record_list;
-    Mask m_event_mask;
-    std::atomic<Status> m_status = NotStarted;
 };
 
 }  // namespace imperative