- 23 4月, 2016 1 次提交
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由 Wang Nan 提交于
This patch introduces 'write_backward' bit to perf_event_attr, which controls the direction of a ring buffer. After set, the corresponding ring buffer is written from end to beginning. This feature is design to support reading from overwritable ring buffer. Ring buffer can be created by mapping a perf event fd. Kernel puts event records into ring buffer, user tooling like perf fetch them from address returned by mmap(). To prevent racing between kernel and tooling, they communicate to each other through 'head' and 'tail' pointers. Kernel maintains 'head' pointer, points it to the next free area (tail of the last record). Tooling maintains 'tail' pointer, points it to the tail of last consumed record (record has already been fetched). Kernel determines the available space in a ring buffer using these two pointers to avoid overwrite unfetched records. By mapping without 'PROT_WRITE', an overwritable ring buffer is created. Different from normal ring buffer, tooling is unable to maintain 'tail' pointer because writing is forbidden. Therefore, for this type of ring buffers, kernel overwrite old records unconditionally, works like flight recorder. This feature would be useful if reading from overwritable ring buffer were as easy as reading from normal ring buffer. However, there's an obscure problem. The following figure demonstrates a full overwritable ring buffer. In this figure, the 'head' pointer points to the end of last record, and a long record 'E' is pending. For a normal ring buffer, a 'tail' pointer would have pointed to position (X), so kernel knows there's no more space in the ring buffer. However, for an overwritable ring buffer, kernel ignore the 'tail' pointer. (X) head . | . V +------+-------+----------+------+---+ |A....A|B.....B|C........C|D....D| | +------+-------+----------+------+---+ Record 'A' is overwritten by event 'E': head | V +--+---+-------+----------+------+---+ |.E|..A|B.....B|C........C|D....D|E..| +--+---+-------+----------+------+---+ Now tooling decides to read from this ring buffer. However, none of these two natural positions, 'head' and the start of this ring buffer, are pointing to the head of a record. Even the full ring buffer can be accessed by tooling, it is unable to find a position to start decoding. The first attempt tries to solve this problem AFAIK can be found from [1]. It makes kernel to maintain 'tail' pointer: updates it when ring buffer is half full. However, this approach introduces overhead to fast path. Test result shows a 1% overhead [2]. In addition, this method utilizes no more tham 50% records. Another attempt can be found from [3], which allows putting the size of an event at the end of each record. This approach allows tooling to find records in a backward manner from 'head' pointer by reading size of a record from its tail. However, because of alignment requirement, it needs 8 bytes to record the size of a record, which is a huge waste. Its performance is also not good, because more data need to be written. This approach also introduces some extra branch instructions to fast path. 'write_backward' is a better solution to this problem. Following figure demonstrates the state of the overwritable ring buffer when 'write_backward' is set before overwriting: head | V +---+------+----------+-------+------+ | |D....D|C........C|B.....B|A....A| +---+------+----------+-------+------+ and after overwriting: head | V +---+------+----------+-------+---+--+ |..E|D....D|C........C|B.....B|A..|E.| +---+------+----------+-------+---+--+ In each situation, 'head' points to the beginning of the newest record. From this record, tooling can iterate over the full ring buffer and fetch records one by one. The only limitation that needs to be considered is back-to-back reading. Due to the non-deterministic of user programs, it is impossible to ensure the ring buffer keeps stable during reading. Consider an extreme situation: tooling is scheduled out after reading record 'D', then a burst of events come, eat up the whole ring buffer (one or multiple rounds). When the tooling process comes back, reading after 'D' is incorrect now. To prevent this problem, we need to find a way to ensure the ring buffer is stable during reading. ioctl(PERF_EVENT_IOC_PAUSE_OUTPUT) is suggested because its overhead is lower than ioctl(PERF_EVENT_IOC_ENABLE). By carefully verifying 'header' pointer, reader can avoid pausing the ring-buffer. For example: /* A union of all possible events */ union perf_event event; p = head = perf_mmap__read_head(); while (true) { /* copy header of next event */ fetch(&event.header, p, sizeof(event.header)); /* read 'head' pointer */ head = perf_mmap__read_head(); /* check overwritten: is the header good? */ if (!verify(sizeof(event.header), p, head)) break; /* copy the whole event */ fetch(&event, p, event.header.size); /* read 'head' pointer again */ head = perf_mmap__read_head(); /* is the whole event good? */ if (!verify(event.header.size, p, head)) break; p += event.header.size; } However, the overhead is high because: a) In-place decoding is not safe. Copying-verifying-decoding is required. b) Fetching 'head' pointer requires additional synchronization. (From Alexei Starovoitov: Even when this trick works, pause is needed for more than stability of reading. When we collect the events into overwrite buffer we're waiting for some other trigger (like all cpu utilization spike or just one cpu running and all others are idle) and when it happens the buffer has valuable info from the past. At this point new events are no longer interesting and buffer should be paused, events read and unpaused until next trigger comes.) This patch utilizes event's default overflow_handler introduced previously. perf_event_output_backward() is created as the default overflow handler for backward ring buffers. To avoid extra overhead to fast path, original perf_event_output() becomes __perf_event_output() and marked '__always_inline'. In theory, there's no extra overhead introduced to fast path. Performance testing: Calling 3000000 times of 'close(-1)', use gettimeofday() to check duration. Use 'perf record -o /dev/null -e raw_syscalls:*' to capture system calls. In ns. Testing environment: CPU : Intel(R) Core(TM) i7-4790 CPU @ 3.60GHz Kernel : v4.5.0 MEAN STDVAR BASE 800214.950 2853.083 PRE1 2253846.700 9997.014 PRE2 2257495.540 8516.293 POST 2250896.100 8933.921 Where 'BASE' is pure performance without capturing. 'PRE1' is test result of pure 'v4.5.0' kernel. 'PRE2' is test result before this patch. 'POST' is test result after this patch. See [4] for the detailed experimental setup. Considering the stdvar, this patch doesn't introduce performance overhead to the fast path. [1] http://lkml.iu.edu/hypermail/linux/kernel/1304.1/04584.html [2] http://lkml.iu.edu/hypermail/linux/kernel/1307.1/00535.html [3] http://lkml.iu.edu/hypermail/linux/kernel/1512.0/01265.html [4] http://lkml.kernel.org/g/56F89DCD.1040202@huawei.comSigned-off-by: NWang Nan <wangnan0@huawei.com> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Acked-by: NAlexei Starovoitov <ast@kernel.org> Cc: <acme@kernel.org> Cc: <pi3orama@163.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Brendan Gregg <brendan.d.gregg@gmail.com> Cc: He Kuang <hekuang@huawei.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: Zefan Li <lizefan@huawei.com> Link: http://lkml.kernel.org/r/1459865478-53413-1-git-send-email-wangnan0@huawei.com [ Fixed the changelog some more. ] Signed-off-by: NIngo Molnar <mingo@kernel.org> Signed-off-by: NIngo Molnar <mingo@kernel.org>
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- 31 3月, 2016 5 次提交
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由 Wang Nan 提交于
Convert perf_output_begin() to __perf_output_begin() and make the later function able to write records from the end of the ring-buffer. Following commits will utilize the 'backward' flag. This is the core patch to support writing to the ring-buffer backwards, which will be introduced by upcoming patches to support reading from overwritable ring-buffers. In theory, this patch should not introduce any extra performance overhead since we use always_inline, but it does not hurt to double check that assumption: When CONFIG_OPTIMIZE_INLINING is disabled, the output object is nearly identical to original one. See: http://lkml.kernel.org/g/56F52E83.70409@huawei.com When CONFIG_OPTIMIZE_INLINING is enabled, the resuling object file becomes smaller: $ size kernel/events/ring_buffer.o* text data bss dec hex filename 4641 4 8 4653 122d kernel/events/ring_buffer.o.old 4545 4 8 4557 11cd kernel/events/ring_buffer.o.new Performance testing results: Calling 3000000 times of 'close(-1)', use gettimeofday() to check duration. Use 'perf record -o /dev/null -e raw_syscalls:*' to capture system calls. In ns. Testing environment: CPU : Intel(R) Core(TM) i7-4790 CPU @ 3.60GHz Kernel : v4.5.0 MEAN STDVAR BASE 800214.950 2853.083 PRE 2253846.700 9997.014 POST 2257495.540 8516.293 Where 'BASE' is pure performance without capturing. 'PRE' is test result of pure 'v4.5.0' kernel. 'POST' is test result after this patch. Considering the stdvar, this patch doesn't hurt performance, within noise margin. For testing details, see: http://lkml.kernel.org/g/56F89DCD.1040202@huawei.comSigned-off-by: NWang Nan <wangnan0@huawei.com> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: <pi3orama@163.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Brendan Gregg <brendan.d.gregg@gmail.com> Cc: He Kuang <hekuang@huawei.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: Zefan Li <lizefan@huawei.com> Link: http://lkml.kernel.org/r/1459147292-239310-4-git-send-email-wangnan0@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
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由 Wang Nan 提交于
Add new ioctl() to pause/resume ring-buffer output. In some situations we want to read from the ring-buffer only when we ensure nothing can write to the ring-buffer during reading. Without this patch we have to turn off all events attached to this ring-buffer to achieve this. This patch is a prerequisite to enable overwrite support for the perf ring-buffer support. Following commits will introduce new methods support reading from overwrite ring buffer. Before reading, caller must ensure the ring buffer is frozen, or the reading is unreliable. Signed-off-by: NWang Nan <wangnan0@huawei.com> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: <pi3orama@163.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Brendan Gregg <brendan.d.gregg@gmail.com> Cc: He Kuang <hekuang@huawei.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: Zefan Li <lizefan@huawei.com> Link: http://lkml.kernel.org/r/1459147292-239310-2-git-send-email-wangnan0@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
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由 Alexander Shishkin 提交于
In order to ensure safe AUX buffer management, we rely on the assumption that pmu::stop() stops its ongoing AUX transaction and not just the hw. This patch documents this requirement for the perf_aux_output_{begin,end}() APIs. Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mathieu Poirier <mathieu.poirier@linaro.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: vince@deater.net Link: http://lkml.kernel.org/r/1457098969-21595-4-git-send-email-alexander.shishkin@linux.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
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由 Alexander Shishkin 提交于
Now that we can ensure that when ring buffer's AUX area is on the way to getting unmapped new transactions won't start, we only need to stop all events that can potentially be writing aux data to our ring buffer. Having done that, we can safely free the AUX pages and corresponding PMU data, as this time it is guaranteed to be the last aux reference holder. This partially reverts: 57ffc5ca ("perf: Fix AUX buffer refcounting") ... which was made to defer deallocation that was otherwise possible from an NMI context. Now it is no longer the case; the last call to rb_free_aux() that drops the last AUX reference has to happen in perf_mmap_close() on that AUX area. Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: vince@deater.net Link: http://lkml.kernel.org/r/87d1qtz23d.fsf@ashishki-desk.ger.corp.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
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由 Alexander Shishkin 提交于
When ring buffer's AUX area is unmapped and rb->aux_mmap_count drops to zero, new AUX transactions into this buffer can still be started, even though the buffer in en route to deallocation. This patch adds a check to perf_aux_output_begin() for rb->aux_mmap_count being zero, in which case there is no point starting new transactions, in other words, the ring buffers that pass a certain point in perf_mmap_close will not have their events sending new data, which clears path for freeing those buffers' pages right there and then, provided that no active transactions are holding the AUX reference. Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: vince@deater.net Link: http://lkml.kernel.org/r/1457098969-21595-2-git-send-email-alexander.shishkin@linux.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
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- 21 3月, 2016 1 次提交
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由 Peter Zijlstra 提交于
Sasha reported: [ 3494.030114] UBSAN: Undefined behaviour in kernel/events/ring_buffer.c:685:22 [ 3494.030647] shift exponent -1 is negative Andrey spotted that this is because: It happens if nr_pages = 0: rb->page_order = ilog2(nr_pages); Fix it by making both assignments conditional on nr_pages; since otherwise they should both be 0 anyway, and will be because of the kzalloc() used to allocate the structure. Reported-by: NSasha Levin <sasha.levin@oracle.com> Reported-by: NAndrey Ryabinin <ryabinin.a.a@gmail.com> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: David Ahern <dsahern@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Link: http://lkml.kernel.org/r/20160129141751.GA407@worktopSigned-off-by: NIngo Molnar <mingo@kernel.org>
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- 22 1月, 2016 1 次提交
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由 Alexander Shishkin 提交于
We are currently using asynchronous deallocation in the error path in AUX mmap code, which is unnecessary and also presents a problem for users that wish to probe for the biggest possible buffer size they can get: they'll get -EINVAL on all subsequent attemts to allocate a smaller buffer before the asynchronous deallocation callback frees up the pages from the previous unsuccessful attempt. Currently, gdb does that for allocating AUX buffers for Intel PT traces. More specifically, overwrite mode of AUX pmus that don't support hardware sg (some implementations of Intel PT, for instance) is limited to only one contiguous high order allocation for its buffer and there is no way of knowing its size without trying. This patch changes error path freeing to be synchronous as there won't be any contenders for the AUX pages at that point. Reported-by: NMarkus Metzger <markus.t.metzger@intel.com> Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: David Ahern <dsahern@gmail.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: vince@deater.net Link: http://lkml.kernel.org/r/1453216469-9509-1-git-send-email-alexander.shishkin@linux.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
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- 23 11月, 2015 1 次提交
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由 Peter Zijlstra 提交于
There were still a number of references to my old Red Hat email address in the kernel source. Remove these while keeping the Red Hat copyright notices intact. Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Signed-off-by: NIngo Molnar <mingo@kernel.org>
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- 04 11月, 2015 1 次提交
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由 Linus Torvalds 提交于
This seems to be a mis-reading of how alpha memory ordering works, and is not backed up by the alpha architecture manual. The helper functions don't do anything special on any other architectures, and the arguments that support them being safe on other architectures also argue that they are safe on alpha. Basically, the "control dependency" is between a previous read and a subsequent write that is dependent on the value read. Even if the subsequent write is actually done speculatively, there is no way that such a speculative write could be made visible to other cpu's until it has been committed, which requires validating the speculation. Note that most weakely ordered architectures (very much including alpha) do not guarantee any ordering relationship between two loads that depend on each other on a control dependency: read A if (val == 1) read B because the conditional may be predicted, and the "read B" may be speculatively moved up to before reading the value A. So we require the user to insert a smp_rmb() between the two accesses to be correct: read A; if (A == 1) smp_rmb() read B Alpha is further special in that it can break that ordering even if the *address* of B depends on the read of A, because the cacheline that is read later may be stale unless you have a memory barrier in between the pointer read and the read of the value behind a pointer: read ptr read offset(ptr) whereas all other weakly ordered architectures guarantee that the data dependency (as opposed to just a control dependency) will order the two accesses. As a result, alpha needs a "smp_read_barrier_depends()" in between those two reads for them to be ordered. The coontrol dependency that "READ_ONCE_CTRL()" and "atomic_read_ctrl()" had was a control dependency to a subsequent *write*, however, and nobody can finalize such a subsequent write without having actually done the read. And were you to write such a value to a "stale" cacheline (the way the unordered reads came to be), that would seem to lose the write entirely. So the things that make alpha able to re-order reads even more aggressively than other weak architectures do not seem to be relevant for a subsequent write. Alpha memory ordering may be strange, but there's no real indication that it is *that* strange. Also, the alpha architecture reference manual very explicitly talks about the definition of "Dependence Constraints" in section 5.6.1.7, where a preceding read dominates a subsequent write. Such a dependence constraint admittedly does not impose a BEFORE (alpha architecture term for globally visible ordering), but it does guarantee that there can be no "causal loop". I don't see how you could avoid such a loop if another cpu could see the stored value and then impact the value of the first read. Put another way: the read and the write could not be seen as being out of order wrt other cpus. So I do not see how these "x_ctrl()" functions can currently be necessary. I may have to eat my words at some point, but in the absense of clear proof that alpha actually needs this, or indeed even an explanation of how alpha could _possibly_ need it, I do not believe these functions are called for. And if it turns out that alpha really _does_ need a barrier for this case, that barrier still should not be "smp_read_barrier_depends()". We'd have to make up some new speciality barrier just for alpha, along with the documentation for why it really is necessary. Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul E McKenney <paulmck@us.ibm.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 12 8月, 2015 2 次提交
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由 Alexander Shishkin 提交于
A question [1] was raised about the use of page::private in AUX buffer allocations, so let's add a clarification about its intended use. The private field and flag are used by perf's rb_alloc_aux() path to tell the pmu driver the size of each high-order allocation, so that the driver can program those appropriately into its hardware. This only matters for PMUs that don't support hardware scatter tables. Otherwise, every page in the buffer is just a page. This patch adds a comment about the private field to the AUX buffer allocation path. [1] http://marc.info/?l=linux-kernel&m=143803696607968Reported-by: NMathieu Poirier <mathieu.poirier@linaro.org> Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1438063204-665-1-git-send-email-alexander.shishkin@linux.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
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由 Ben Hutchings 提交于
If rb->aux_refcount is decremented to zero before rb->refcount, __rb_free_aux() may be called twice resulting in a double free of rb->aux_pages. Fix this by adding a check to __rb_free_aux(). Signed-off-by: NBen Hutchings <ben@decadent.org.uk> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Fixes: 57ffc5ca ("perf: Fix AUX buffer refcounting") Link: http://lkml.kernel.org/r/1437953468.12842.17.camel@decadent.org.ukSigned-off-by: NIngo Molnar <mingo@kernel.org>
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- 06 7月, 2015 1 次提交
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由 Peter Zijlstra 提交于
Its currently possible to drop the last refcount to the aux buffer from NMI context, which results in the expected fireworks. The refcounting needs a bigger overhaul, but to cure the immediate problem, delay the freeing by using an irq_work. Reviewed-and-tested-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com> Reported-by: NVince Weaver <vincent.weaver@maine.edu> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150618103249.GK19282@twins.programming.kicks-ass.netSigned-off-by: NIngo Molnar <mingo@kernel.org>
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- 28 5月, 2015 1 次提交
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由 Paul E. McKenney 提交于
The current formulation of control dependencies fails on DEC Alpha, which does not respect dependencies of any kind unless an explicit memory barrier is provided. This means that the current fomulation of control dependencies fails on Alpha. This commit therefore creates a READ_ONCE_CTRL() that has the same overhead on non-Alpha systems, but causes Alpha to produce the needed ordering. This commit also applies READ_ONCE_CTRL() to the one known use of control dependencies. Use of READ_ONCE_CTRL() also has the beneficial effect of adding a bit of self-documentation to control dependencies. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
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- 27 5月, 2015 1 次提交
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由 Alexander Shishkin 提交于
PMUs that don't support hardware scatter tables require big contiguous chunks of memory and a PMI to switch between them. However, in overwrite using a PMI for this purpose adds extra overhead that the users would like to avoid. Thus, in overwrite mode for such PMUs we can only allow one contiguous chunk for the entire requested buffer. This patch changes the behavior accordingly, so that if the buddy allocator fails to come up with a single high-order chunk for the entire requested buffer, the allocation will fail. Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: acme@infradead.org Cc: adrian.hunter@intel.com Cc: hpa@zytor.com Link: http://lkml.kernel.org/r/1432308626-18845-2-git-send-email-alexander.shishkin@linux.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
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- 02 4月, 2015 6 次提交
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由 Alexander Shishkin 提交于
When AUX area gets a certain amount of new data, we want to wake up userspace to collect it. This adds a new control to specify how much data will cause a wakeup. This is then passed down to pmu drivers via output handle's "wakeup" field, so that the driver can find the nearest point where it can generate an interrupt. We repurpose __reserved_2 in the event attribute for this, even though it was never checked to be zero before, aux_watermark will only matter for new AUX-aware code, so the old code should still be fine. Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kaixu Xia <kaixu.xia@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Robert Richter <rric@kernel.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: acme@infradead.org Cc: adrian.hunter@intel.com Cc: kan.liang@intel.com Cc: markus.t.metzger@intel.com Cc: mathieu.poirier@linaro.org Link: http://lkml.kernel.org/r/1421237903-181015-10-git-send-email-alexander.shishkin@linux.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
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由 Alexander Shishkin 提交于
This adds support for overwrite mode in the AUX area, which means "keep collecting data till you're stopped", turning AUX area into a circular buffer, where new data overwrites old data. It does not depend on data buffer's overwrite mode, so that it doesn't lose sideband data that is instrumental for processing AUX data. Overwrite mode is enabled at mapping AUX area read only. Even though aux_tail in the buffer's user page might be user writable, it will be ignored in this mode. A PERF_RECORD_AUX with PERF_AUX_FLAG_OVERWRITE set is written to the perf data stream every time an event writes new data to the AUX area. The pmu driver might not be able to infer the exact beginning of the new data in each snapshot, some drivers will only provide the tail, which is aux_offset + aux_size in the AUX record. Consumer has to be able to tell the new data from the old one, for example, by means of time stamps if such are provided in the trace. Consumer is also responsible for disabling any events that might write to the AUX area (thus potentially racing with the consumer) before collecting the data. Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kaixu Xia <kaixu.xia@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Robert Richter <rric@kernel.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: acme@infradead.org Cc: adrian.hunter@intel.com Cc: kan.liang@intel.com Cc: markus.t.metzger@intel.com Cc: mathieu.poirier@linaro.org Link: http://lkml.kernel.org/r/1421237903-181015-9-git-send-email-alexander.shishkin@linux.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
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由 Alexander Shishkin 提交于
For pmus that wish to write data to ring buffer's AUX area, provide perf_aux_output_{begin,end}() calls to initiate/commit data writes, similarly to perf_output_{begin,end}. These also use the same output handle structure. Also, similarly to software counterparts, these will direct inherited events' output to parents' ring buffers. After the perf_aux_output_begin() returns successfully, handle->size is set to the maximum amount of data that can be written wrt aux_tail pointer, so that no data that the user hasn't seen will be overwritten, therefore this should always be called before hardware writing is enabled. On success, this will return the pointer to pmu driver's private structure allocated for this aux area by pmu::setup_aux. Same pointer can also be retrieved using perf_get_aux() while hardware writing is enabled. PMU driver should pass the actual amount of data written as a parameter to perf_aux_output_end(). All hardware writes should be completed and visible before this one is called. Additionally, perf_aux_output_skip() will adjust output handle and aux_head in case some part of the buffer has to be skipped over to maintain hardware's alignment constraints. Nested writers are forbidden and guards are in place to catch such attempts. Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kaixu Xia <kaixu.xia@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Robert Richter <rric@kernel.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: acme@infradead.org Cc: adrian.hunter@intel.com Cc: kan.liang@intel.com Cc: markus.t.metzger@intel.com Cc: mathieu.poirier@linaro.org Link: http://lkml.kernel.org/r/1421237903-181015-8-git-send-email-alexander.shishkin@linux.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
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由 Alexander Shishkin 提交于
For pmus that don't support scatter-gather for AUX data in hardware, it might still make sense to implement software double buffering to avoid losing data while the user is reading data out. For this purpose, add a pmu capability that guarantees multiple high-order chunks for AUX buffer, so that the pmu driver can do switchover tricks. To make use of this feature, add PERF_PMU_CAP_AUX_SW_DOUBLEBUF to your pmu's capability mask. This will make the ring buffer AUX allocation code ensure that the biggest high order allocation for the aux buffer pages is no bigger than half of the total requested buffer size, thus making sure that the buffer has at least two high order allocations. Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kaixu Xia <kaixu.xia@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Robert Richter <rric@kernel.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: acme@infradead.org Cc: adrian.hunter@intel.com Cc: kan.liang@intel.com Cc: markus.t.metzger@intel.com Cc: mathieu.poirier@linaro.org Link: http://lkml.kernel.org/r/1421237903-181015-5-git-send-email-alexander.shishkin@linux.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
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由 Alexander Shishkin 提交于
Some pmus (such as BTS or Intel PT without multiple-entry ToPA capability) don't support scatter-gather and will prefer larger contiguous areas for their output regions. This patch adds a new pmu capability to request higher order allocations. Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kaixu Xia <kaixu.xia@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Robert Richter <rric@kernel.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: acme@infradead.org Cc: adrian.hunter@intel.com Cc: kan.liang@intel.com Cc: markus.t.metzger@intel.com Cc: mathieu.poirier@linaro.org Link: http://lkml.kernel.org/r/1421237903-181015-4-git-send-email-alexander.shishkin@linux.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
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由 Peter Zijlstra 提交于
This patch introduces "AUX space" in the perf mmap buffer, intended for exporting high bandwidth data streams to userspace, such as instruction flow traces. AUX space is a ring buffer, defined by aux_{offset,size} fields in the user_page structure, and read/write pointers aux_{head,tail}, which abide by the same rules as data_* counterparts of the main perf buffer. In order to allocate/mmap AUX, userspace needs to set up aux_offset to such an offset that will be greater than data_offset+data_size and aux_size to be the desired buffer size. Both need to be page aligned. Then, same aux_offset and aux_size should be passed to mmap() call and if everything adds up, you should have an AUX buffer as a result. Pages that are mapped into this buffer also come out of user's mlock rlimit plus perf_event_mlock_kb allowance. Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Acked-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kaixu Xia <kaixu.xia@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Robert Richter <rric@kernel.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: acme@infradead.org Cc: adrian.hunter@intel.com Cc: kan.liang@intel.com Cc: markus.t.metzger@intel.com Cc: mathieu.poirier@linaro.org Link: http://lkml.kernel.org/r/1421237903-181015-3-git-send-email-alexander.shishkin@linux.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
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- 04 2月, 2015 1 次提交
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由 Jiri Olsa 提交于
Currently we flag available data (via poll syscall) on perf fd with POLL_IN macro, which is normally used for SIGIO interface. We've been lucky, because POLLIN (0x1) is subset of POLL_IN (0x20001) and sys_poll (do_pollfd function) cut the extra bit out (0x20000). Signed-off-by: NJiri Olsa <jolsa@kernel.org> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Stephane Eranian <eranian@google.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1422467678-22341-1-git-send-email-jolsa@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
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- 11 12月, 2013 1 次提交
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由 Peter Zijlstra 提交于
Remove a full barrier from the ring-buffer write path by relying on a control dependency to order a LOAD -> STORE scenario. Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Signed-off-by: NPeter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-8alv40z6ikk57jzbaobnxrjl@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
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- 06 11月, 2013 6 次提交
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由 Peter Zijlstra 提交于
Signed-off-by: NPeter Zijlstra <peterz@infradead.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: Michael Ellerman <michael@ellerman.id.au> Cc: Michael Neuling <mikey@neuling.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: james.hogan@imgtec.com Cc: Vince Weaver <vince@deater.net> Cc: Victor Kaplansky <VICTORK@il.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Anton Blanchard <anton@samba.org> Link: http://lkml.kernel.org/n/tip-9s5mze78gmlz19agt39i8rii@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
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由 Peter Zijlstra 提交于
Rewrite the handle address calculation code to be clearer. Saves 8 bytes on x86_64-defconfig. Signed-off-by: NPeter Zijlstra <peterz@infradead.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: Michael Ellerman <michael@ellerman.id.au> Cc: Michael Neuling <mikey@neuling.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: james.hogan@imgtec.com Cc: Vince Weaver <vince@deater.net> Cc: Victor Kaplansky <VICTORK@il.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Anton Blanchard <anton@samba.org> Link: http://lkml.kernel.org/n/tip-3trb2n2henb9m27tncef3ag7@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
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由 Peter Zijlstra 提交于
Avoid touching the lost_event and sample_data cachelines twince. Its not like we end up doing less work, but it might help to keep all accesses to these cachelines in one place. Due to code shuffle, this looses 4 bytes on x86_64-defconfig. Signed-off-by: NPeter Zijlstra <peterz@infradead.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: Michael Ellerman <michael@ellerman.id.au> Cc: Michael Neuling <mikey@neuling.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: james.hogan@imgtec.com Cc: Vince Weaver <vince@deater.net> Cc: Victor Kaplansky <VICTORK@il.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Anton Blanchard <anton@samba.org> Link: http://lkml.kernel.org/n/tip-zfxnc58qxj0eawdoj31hhupv@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
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由 Peter Zijlstra 提交于
There's no point in re-doing the memory-barrier when we fail the cmpxchg(). Also placing it after the space reservation loop makes it clearer it only separates the userpage->tail read from the data stores. Signed-off-by: NPeter Zijlstra <peterz@infradead.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: Michael Ellerman <michael@ellerman.id.au> Cc: Michael Neuling <mikey@neuling.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: james.hogan@imgtec.com Cc: Vince Weaver <vince@deater.net> Cc: Victor Kaplansky <VICTORK@il.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Anton Blanchard <anton@samba.org> Link: http://lkml.kernel.org/n/tip-c19u6egfldyx86tpyc3zgkw9@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
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由 Peter Zijlstra 提交于
Add unlikely() annotations to 'slow' paths: When having a sampling event but no output buffer; you have bigger issues -- also the bail is still faster than actually doing the work. When having a sampling event but a control page only buffer, you have bigger issues -- again the bail is still faster than actually doing work. Optimize for the case where you're not loosing events -- again, not doing the work is still faster but make sure that when you have to actually do work its as fast as possible. The typical watermark is 1/2 the buffer size, so most events will not take this path. Shrinks perf_output_begin() by 16 bytes on x86_64-defconfig. Signed-off-by: NPeter Zijlstra <peterz@infradead.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: Michael Ellerman <michael@ellerman.id.au> Cc: Michael Neuling <mikey@neuling.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: james.hogan@imgtec.com Cc: Vince Weaver <vince@deater.net> Cc: Victor Kaplansky <VICTORK@il.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Anton Blanchard <anton@samba.org> Link: http://lkml.kernel.org/n/tip-wlg3jew3qnutm8opd0hyeuwn@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
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由 Peter Zijlstra 提交于
By using CIRC_SPACE() we can obviate the need for perf_output_space(). Shrinks the size of perf_output_begin() by 17 bytes on x86_64-defconfig. Signed-off-by: NPeter Zijlstra <peterz@infradead.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: Michael Ellerman <michael@ellerman.id.au> Cc: Michael Neuling <mikey@neuling.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: james.hogan@imgtec.com Cc: Vince Weaver <vince@deater.net> Cc: Victor Kaplansky <VICTORK@il.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Anton Blanchard <anton@samba.org> Link: http://lkml.kernel.org/n/tip-vtb0xb0llebmsdlfn1v5vtfj@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
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- 29 10月, 2013 1 次提交
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由 Peter Zijlstra 提交于
The PPC64 people noticed a missing memory barrier and crufty old comments in the perf ring buffer code. So update all the comments and add the missing barrier. When the architecture implements local_t using atomic_long_t there will be double barriers issued; but short of introducing more conditional barrier primitives this is the best we can do. Reported-by: NVictor Kaplansky <victork@il.ibm.com> Tested-by: NVictor Kaplansky <victork@il.ibm.com> Signed-off-by: NPeter Zijlstra <peterz@infradead.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: michael@ellerman.id.au Cc: Paul McKenney <paulmck@linux.vnet.ibm.com> Cc: Michael Neuling <mikey@neuling.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: anton@samba.org Cc: benh@kernel.crashing.org Link: http://lkml.kernel.org/r/20131025173749.GG19466@laptop.lanSigned-off-by: NIngo Molnar <mingo@kernel.org>
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- 01 5月, 2013 1 次提交
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由 Jiri Olsa 提交于
If we allocate perf ring buffer with the size of single (user) page, we will get memory corruption when releasing itin rb_free_work function (for CONFIG_PERF_USE_VMALLOC option). For single page sized ring buffer the page_order is -1 (because nr_pages is 0). This needs to be recognized in the rb_free_work function to release proper amount of pages. Adding data_page_nr function that returns number of allocated data pages. Customizing the rest of the code to use it. Reported-by: NJan Stancek <jstancek@redhat.com> Original-patch-by: NPeter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl> Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: NJiri Olsa <jolsa@redhat.com> Link: http://lkml.kernel.org/r/20130319143509.GA1128@krava.brq.redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
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- 21 3月, 2013 1 次提交
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由 Stephane Eranian 提交于
This patch fixes a flaw in perf_output_space(). In case the size of the space needed is bigger than the actual buffer size, there may be situations where the function would return true (i.e., there is space) when it should not. head > offset due to rounding of the masking logic. The problem can be tested by activating BTS on Intel processors. A BTS record can be as big as 16 pages. The following command fails: $ perf record -m 4 -c 1 -e branches:u my_test_program You will get a buffer corruption with this. Perf report won't be able to parse the perf.data. The fix is to first check that the requested space is smaller than the buffer size. If so, then the masking logic will work fine. If not, then there is no chance the record can be saved and it will be gracefully handled by upper code layers. [ In v2, we also make the logic for the writable more explicit by renaming it to rb->overwrite because it tells whether or not the buffer can overwrite its tail (suggested by PeterZ). ] Signed-off-by: NStephane Eranian <eranian@google.com> Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl> Cc: peterz@infradead.org Cc: jolsa@redhat.com Cc: fweisbec@gmail.com Link: http://lkml.kernel.org/r/20130318133327.GA3056@quadSigned-off-by: NIngo Molnar <mingo@kernel.org>
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- 10 8月, 2012 2 次提交
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由 Jiri Olsa 提交于
Introducing perf_output_skip function to be able to skip data within the perf ring buffer. When writing data into perf ring buffer we first reserve needed place in ring buffer and then copy the actual data. There's a possibility we won't be able to fill all the reserved size with data, so we need a way to skip the remaining bytes. This is going to be useful when storing the user stack dump, where we might end up with less data than we originally requested. Signed-off-by: NJiri Olsa <jolsa@redhat.com> Acked-by: NFrederic Weisbecker <fweisbec@gmail.com> Cc: "Frank Ch. Eigler" <fche@redhat.com> Cc: Arun Sharma <asharma@fb.com> Cc: Benjamin Redelings <benjamin.redelings@nescent.org> Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Frank Ch. Eigler <fche@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Robert Richter <robert.richter@amd.com> Cc: Stephane Eranian <eranian@google.com> Cc: Tom Zanussi <tzanussi@gmail.com> Cc: Ulrich Drepper <drepper@gmail.com> Link: http://lkml.kernel.org/r/1344345647-11536-5-git-send-email-jolsa@redhat.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
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由 Frederic Weisbecker 提交于
Adding a generic way to use __output_copy function with specific copy function via DEFINE_PERF_OUTPUT_COPY macro. Using this to add new __output_copy_user function, that provides output copy from user pointers. For x86 the copy_from_user_nmi function is used and __copy_from_user_inatomic for the rest of the architectures. This new function will be used in user stack dump on sample, coming in next patches. Signed-off-by: NJiri Olsa <jolsa@redhat.com> Cc: "Frank Ch. Eigler" <fche@redhat.com> Cc: Arun Sharma <asharma@fb.com> Cc: Benjamin Redelings <benjamin.redelings@nescent.org> Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Frank Ch. Eigler <fche@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Robert Richter <robert.richter@amd.com> Cc: Stephane Eranian <eranian@google.com> Cc: Tom Zanussi <tzanussi@gmail.com> Cc: Ulrich Drepper <drepper@gmail.com> Link: http://lkml.kernel.org/r/1344345647-11536-4-git-send-email-jolsa@redhat.comSigned-off-by: NFrederic Weisbecker <fweisbec@gmail.com> Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
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- 02 1月, 2012 1 次提交
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由 Al Viro 提交于
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk> Signed-off-by: NJiri Kosina <jkosina@suse.cz>
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- 05 12月, 2011 1 次提交
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由 Peter Zijlstra 提交于
When you do: $ perf record -e cycles,cycles,cycles noploop 10 You expect about 10,000 samples for each event, i.e., 10s at 1000samples/sec. However, this is not what's happening. You get much fewer samples, maybe 3700 samples/event: $ perf report -D | tail -15 Aggregated stats: TOTAL events: 10998 MMAP events: 66 COMM events: 2 SAMPLE events: 10930 cycles stats: TOTAL events: 3644 SAMPLE events: 3644 cycles stats: TOTAL events: 3642 SAMPLE events: 3642 cycles stats: TOTAL events: 3644 SAMPLE events: 3644 On a Intel Nehalem or even AMD64, there are 4 counters capable of measuring cycles, so there is plenty of space to measure those events without multiplexing (even with the NMI watchdog active). And even with multiplexing, we'd expect roughly the same number of samples per event. The root of the problem was that when the event that caused the buffer to become full was not the first event passed on the cmdline, the user notification would get lost. The notification was sent to the file descriptor of the overflowed event but the perf tool was not polling on it. The perf tool aggregates all samples into a single buffer, i.e., the buffer of the first event. Consequently, it assumes notifications for any event will come via that descriptor. The seemingly straight forward solution of moving the waitq into the ringbuffer object doesn't work because of life-time issues. One could perf_event_set_output() on a fd that you're also blocking on and cause the old rb object to be freed while its waitq would still be referenced by the blocked thread -> FAIL. Therefore link all events to the ringbuffer and broadcast the wakeup from the ringbuffer object to all possible events that could be waited upon. This is rather ugly, and we're open to better solutions but it works for now. Reported-by: NStephane Eranian <eranian@google.com> Finished-by: NStephane Eranian <eranian@google.com> Reviewed-by: NStephane Eranian <eranian@google.com> Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20111126014731.GA7030@quadSigned-off-by: NIngo Molnar <mingo@elte.hu>
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- 01 7月, 2011 3 次提交
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由 Peter Zijlstra 提交于
Since only samples call perf_output_sample() its much saner (and more correct) to put the sample logic in there than in the perf_output_begin()/perf_output_end() pair. Saves a useless argument, reduces conditionals and shrinks struct perf_output_handle, win! Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/n/tip-2crpvsx3cqu67q3zqjbnlpsc@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@elte.hu>
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由 Peter Zijlstra 提交于
The nmi parameter indicated if we could do wakeups from the current context, if not, we would set some state and self-IPI and let the resulting interrupt do the wakeup. For the various event classes: - hardware: nmi=0; PMI is in fact an NMI or we run irq_work_run from the PMI-tail (ARM etc.) - tracepoint: nmi=0; since tracepoint could be from NMI context. - software: nmi=[0,1]; some, like the schedule thing cannot perform wakeups, and hence need 0. As one can see, there is very little nmi=1 usage, and the down-side of not using it is that on some platforms some software events can have a jiffy delay in wakeup (when arch_irq_work_raise isn't implemented). The up-side however is that we can remove the nmi parameter and save a bunch of conditionals in fast paths. Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl> Cc: Michael Cree <mcree@orcon.net.nz> Cc: Will Deacon <will.deacon@arm.com> Cc: Deng-Cheng Zhu <dengcheng.zhu@gmail.com> Cc: Anton Blanchard <anton@samba.org> Cc: Eric B Munson <emunson@mgebm.net> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Paul Mundt <lethal@linux-sh.org> Cc: David S. Miller <davem@davemloft.net> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Jason Wessel <jason.wessel@windriver.com> Cc: Don Zickus <dzickus@redhat.com> Link: http://lkml.kernel.org/n/tip-agjev8eu666tvknpb3iaj0fg@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@elte.hu>
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由 Vince Weaver 提交于
Since 2.6.36 (specifically commit d57e34fd ("perf: Simplify the ring-buffer logic: make perf_buffer_alloc() do everything needed"), the perf_buffer_init_code() has been mis-setting the buffer watermark if perf_event_attr.wakeup_events has a non-zero value. This is because perf_event_attr.wakeup_events is a union with perf_event_attr.wakeup_watermark. This commit re-enables the check for perf_event_attr.watermark being set before continuing with setting a non-default watermark. This bug is most noticable when you are trying to use PERF_IOC_REFRESH with a value larger than one and perf_event_attr.wakeup_events is set to one. In this case the buffer watermark will be set to 1 and you will get extraneous POLL_IN overflows rather than POLL_HUP as expected. [ avoid using attr.wakeup_events when attr.watermark is set ] Signed-off-by: NVince Weaver <vweaver1@eecs.utk.edu> Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl> Cc: <stable@kernel.org> Link: http://lkml.kernel.org/r/alpine.DEB.2.00.1106011506390.5384@cl320.eecs.utk.eduSigned-off-by: NIngo Molnar <mingo@elte.hu>
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- 09 6月, 2011 1 次提交
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由 Frederic Weisbecker 提交于
And create the internal perf events header. v2: Keep an internal inlined perf_output_copy() Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com> Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl> Cc: Borislav Petkov <bp@alien8.de> Cc: Stephane Eranian <eranian@google.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/1305827704-5607-1-git-send-email-fweisbec@gmail.com [ v3: use clearer 'ring_buffer' and 'rb' naming ] Signed-off-by: NIngo Molnar <mingo@elte.hu>
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