Android systemace 工具，通过ADB调用atrace工具。但是，我不太了解跟踪文件的格式。显然，它与linux ftrace工具非常相似，但存在一些差异。主要区别在于它不使用系统。映射文件，但它将所有信息包含到跟踪文件中。此外，还有新的B|E条目是android特定的。
Android源代码中有一些关于这种格式的信息:http://androidxref.com/4.1.1/xref/external/chromium-trace/src/tracing/linux_perf_importer.js
然而，在该文档中我们可以读到该格式属于Linux Perf Tool。我不这么认为，linux perf给出了一个非常不同的输出格式…(除非一些特殊的配置是活动的…)
我的问题是:有没有人知道我在哪里可以找到一个关于android跟踪文件生成的官方文档与atrace工具从adb?
这个格式你熟悉吗?
# tracer: nop
#
# entries-in-buffer/entries-written: 66427/66427 #P:2
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
atrace-1724 [000] d..3 14186.680000: sched_switch: prev_comm=atrace prev_pid=1724 prev_prio=120 prev_state=S ==> next_comm=swapper/0 next_pid=0 next_prio=120
<idle>-0 [000] d.h7 14186.690000: sched_wakeup: comm=tfm_b6bcf800 pid=1714 prio=35 success=1 target_cpu=000
<idle>-0 [000] d..3 14186.690000: sched_switch: prev_comm=swapper/0 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=tfm_b6bcf800 next_pid=1714 next_prio=35
tfm_b6bcf800-1714 [000] d..3 14186.690000: sched_switch: prev_comm=tfm_b6bcf800 prev_pid=1714 prev_prio=35 prev_state=D|W ==> next_comm=swapper/0 next_pid=0 next_prio=120
<idle>-0 [001] d.h3 14186.690000: sched_wakeup: comm=Player Aud Mixe pid=146 prio=35 success=1 target_cpu=001
<idle>-0 [001] d..3 14186.690000: sched_switch: prev_comm=swapper/1 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=Player Aud Mixe next_pid=146 next_prio=35
Player Aud Mixe-146 [001] d..3 14186.690000: sched_switch: prev_comm=Player Aud Mixe prev_pid=146 prev_prio=35 prev_state=D ==> next_comm=swapper/1 next_pid=0 next_prio=120
<idle>-0 [001] d.h3 14186.690000: sched_wakeup: comm=Player Aud Mixe pid=146 prio=35 success=1 target_cpu=001
<idle>-0 [001] d..3 14186.690000: sched_switch: prev_comm=swapper/1 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=Player Aud Mixe next_pid=146 next_prio=35
Player Aud Mixe-146 [001] d..3 14186.690000: sched_switch: prev_comm=Player Aud Mixe prev_pid=146 prev_prio=35 prev_state=S ==> next_comm=swapper/1 next_pid=0 next_prio=120
<idle>-0 [001] d.h3 14186.700000: sched_wakeup: comm=Player Aud Mixe pid=146 prio=35 success=1 target_cpu=001
<idle>-0 [001] d..3 14186.700000: sched_switch: prev_comm=swapper/1 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=Player Aud Mixe next_pid=146 next_prio=35
EventThread-110 [001] d..5 14190.100000: sched_wakeup: comm=SurfaceFlinger pid=103 prio=112 success=1 target_cpu=001
EventThread-110 [001] d..3 14190.100000: sched_switch: prev_comm=EventThread prev_pid=110 prev_prio=111 prev_state=S ==> next_comm=SurfaceFlinger next_pid=103 next_prio=112
SurfaceFlinger-103 [001] ...1 14190.100000: tracing_mark_write: B|96|onMessageReceived
SurfaceFlinger-103 [001] ...1 14190.100000: tracing_mark_write: B|96|handleTransaction
SurfaceFlinger-103 [001] ...1 14190.100000: tracing_mark_write: B|96|doTransaction
SurfaceFlinger-103 [001] ...1 14190.100000: tracing_mark_write: E
SurfaceFlinger-103 [001] ...1 14190.100000: tracing_mark_write: E
SurfaceFlinger-103 [001] ...1 14190.100000: tracing_mark_write: B|96|handleMessageInvalidate
SurfaceFlinger-103 [001] ...1 14190.100000: tracing_mark_write: E
SurfaceFlinger-103 [001] ...1 14190.100000: tracing_mark_write: E
SurfaceFlinger-103 [001] ...1 14190.100000: tracing_mark_write: B|96|onMessageReceived
SurfaceFlinger-103 [001] ...1 14190.100000: tracing_mark_write: B|96|handleMessageRefresh
SurfaceFlinger-103 [001] ...1 14190.100000: tracing_mark_write: B|96|rebuildLayerStacks
SurfaceFlinger-103 [001] ...1 14190.100000: tracing_mark_write: B|96|computeVisibleRegions
SurfaceFlinger-103 [001] ...1 14190.100000: tracing_mark_write: E
SurfaceFlinger-103 [001] ...1 14190.100000: tracing_mark_write: E
SurfaceFlinger-103 [001] ...1 14190.100000: tracing_mark_write: B|96|doComposition
SurfaceFlinger-103 [001] d.h4 14190.100000: sched_wakeup: comm=surfaceflinger pid=96 prio=120 success=1 target_cpu=001
SurfaceFlinger-103 [001] d..3 14190.100000: sched_switch: prev_comm=SurfaceFlinger prev_pid=103 prev_prio=112 prev_state=R ==> next_comm=surfaceflinger next_pid=96 next_prio=120
好了，现在确定了:格式属于ftrace工具。Android atrace是ftrace build的扩展，以方便配置。ftrace的官方文档显示，该输出格式可以通过以下方式直接生成:
root@adroid:# echo 1 > /sys/kernel/debug/tracing/events/sched/sched_switch/enable
root@adroid:# echo 1 > /sys/kernel/debug/tracing/tracing_on
root@adroid:# cat /sys/kernel/debug/tracing/trace > mytracefile.txt
root@adroid:# echo 0 > /sys/kernel/debug/tracing/tracing_on
root@adroid:# echo 0 > /sys/kernel/debug/tracing/events/sched/sched_switch/enable
官方文档:http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/trace/ftrace.txt
# cat trace
# tracer: nop
#
# entries-in-buffer/entries-written: 77/77 #P:8
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
<idle>-0 [007] d... 2440.707395: sched_switch: prev_comm=swapper/7 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=snapshot-test-2 next_pid=2243 next_prio=120
snapshot-test-2-2229 [002] d... 2440.707438: sched_switch: prev_comm=snapshot-test-2 prev_pid=2229 prev_prio=120 prev_state=S ==> next_comm=swapper/2 next_pid=0 next_prio=120
[...]
认为,
很棒的文章，但是不要忘记挂载调试文件系统，
"mount -t debugfs none /sys/kernel/debug" or
"mount -o rw,remount -t debugfs none /sys/kernel/debug"
否则你将不会得到像
这样的内容"error open/sys/kernel/debug/tracing/options/overwrite: No such .文件或目录"
运行atrace
这里有更多有用的信息http://rahulonblog.blogspot.se/2013/06/how-to-enable-debugfs-in-kernel.html