diff --git a/easy-fs-fuse/src/main.rs b/easy-fs-fuse/src/main.rs
index d36d566d1cf5693927ebe7ad4fe423f38a8a014f..cf07b6186fa002c667bf09b02140aa2acb0da03f 100644
--- a/easy-fs-fuse/src/main.rs
+++ b/easy-fs-fuse/src/main.rs
@@ -56,13 +56,13 @@ fn easy_fs_pack() -> std::io::Result<()> {
             .write(true)
             .create(true)
             .open(format!("{}{}", target_path, "fs.img"))?;
-        f.set_len(128 * 2048 * 512).unwrap();
+        f.set_len(16 * 2048 * 512).unwrap();
         f
     })));
-    // 128MiB, at most 4095 files
+    // 16MiB, at most 4095 files
     let efs = EasyFileSystem::create(
         block_file.clone(),
-        128 * 2048,
+        16 * 2048,
         1,
     );
     let root_inode = Arc::new(EasyFileSystem::root_inode(&efs));
diff --git a/os/Makefile b/os/Makefile
index 07c10082183664d43368fd9bee06a1fbca0f7d12..864a4e438ccad8e40fd590afb9b6ce5951551d03 100644
--- a/os/Makefile
+++ b/os/Makefile
@@ -49,7 +49,7 @@ env:
 
 sdcard: fs-img
 	@echo "Are you sure write to $(SDCARD) ? [y/N] " && read ans && [ $${ans:-N} = y ]
-	@sudo dd if=/dev/zero of=$(SDCARD) bs=1048576 count=256
+	@sudo dd if=/dev/zero of=$(SDCARD) bs=1048576 count=32
 	@sudo dd if=$(FS_IMG) of=$(SDCARD)
 
 $(KERNEL_BIN): kernel
@@ -57,7 +57,7 @@ $(KERNEL_BIN): kernel
 
 fs-img: $(APPS)
 	@cd ../user && make build
-	@rm $(FS_IMG)
+	@rm $(FS_IMG) -f
 	@cd ../easy-fs-fuse && cargo run --release -- -s ../user/src/bin/ -t ../user/target/riscv64gc-unknown-none-elf/release/
 
 $(APPS):
diff --git a/os/src/timer.rs b/os/src/timer.rs
index 92d50e3ade2b54f5b935d44f7948bb72c12b7ff8..ad226e64490b92c16dac3593ce40362586d0c78b 100644
--- a/os/src/timer.rs
+++ b/os/src/timer.rs
@@ -15,4 +15,4 @@ pub fn get_time_ms() -> usize {
 
 pub fn set_next_trigger() {
     set_timer(get_time() + CLOCK_FREQ / TICKS_PER_SEC);
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/race_adder.rs b/user/src/bin/race_adder.rs
index 44d653fd5f2962e3e3e505236d0a745193916df9..dabead160e8bd1c1f03d69987ed9cd4615baa112 100644
--- a/user/src/bin/race_adder.rs
+++ b/user/src/bin/race_adder.rs
@@ -5,20 +5,21 @@
 extern crate user_lib;
 extern crate alloc;
 
-use user_lib::{exit, thread_create, waittid};
+use user_lib::{exit, thread_create, waittid, get_time};
 use alloc::vec::Vec;
 
 static mut A: usize = 0;
-const PER_THREAD: usize = 10000000;
-const THREAD_COUNT: usize = 50;
+const PER_THREAD: usize = 2000000;
+const THREAD_COUNT: usize = 8;
 
 unsafe fn f() -> ! {
+    let start = get_time();
     for _ in 0..PER_THREAD {
         let a = &mut A as *mut usize;
         let cur = a.read_volatile();
         a.write_volatile(cur + 1);
     }
-    exit(0)
+    exit((get_time() - start) as i32)
 }
 
 #[no_mangle]
@@ -27,10 +28,13 @@ pub fn main() -> i32 {
     for _ in 0..THREAD_COUNT {
         v.push(thread_create(f as usize) as usize);
     }
+    let mut time_cost = Vec::new();
     for tid in v.iter() {
-        waittid(*tid);
+        time_cost.push(waittid(*tid));
+    }
+    for (i, cost) in time_cost.iter().enumerate() {
+        println!("cost of thread#{} is {}ms", i, cost);
     }
     assert_eq!(unsafe { A }, PER_THREAD * THREAD_COUNT);
-    println!("total = {}", unsafe { A });
     0
 }
diff --git a/user/src/linker.ld b/user/src/linker.ld
index 7273618c9f6b2cb497b34e1ffae692b79fcce40a..02f7b6bf583b6e26ab818f3f997edad2cbc0addb 100644
--- a/user/src/linker.ld
+++ b/user/src/linker.ld
@@ -2,7 +2,7 @@
 OUTPUT_ARCH(riscv)
 ENTRY(_start)
 
-BASE_ADDRESS = 0x0;
+BASE_ADDRESS = 0x10000;
 
 SECTIONS
 {
@@ -29,4 +29,4 @@ SECTIONS
         *(.eh_frame)
         *(.debug*)
     }
-}
\ No newline at end of file
+}