Messages in this thread | | | Date | Sun, 6 Dec 2009 12:50:40 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] perf/sched: fix for getting task's execute time |
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* Peter Zijlstra <peterz@infradead.org> wrote:
> On Sun, 2009-12-06 at 12:05 +0100, Peter Zijlstra wrote: > > On Sun, 2009-12-06 at 18:57 +0800, Xiao Guangrong wrote: > > > In current code, we get task's execute time by reading > > > "/proc/<pid>/sched" file, it's wrong if the task is created > > > by pthread_create(), because every thread task has same pid. > > > So, the correct way is reading "/proc/<ppid>/task/<tid>/sched" > > > file. > > > > > > This patch also remove redundant include files since <sys/types.h> > > > is included in "perf.h" > > > > We really should not be using these proc files but instead make sure > > this information gets transferred through a tracepoint or similar. > > > > Reading these proc files is too prone to races.
yeah. Ideally we'd want all valuable information that is available via /proc to be available via perf events as well. In the future it should be possible to run perf even without /proc mounted for example.
Furthermore it's good for consistency and simplicity as well, plus it's faster too to get the information from the perf syscall and mmap-ed ringbuffer than to read things via /proc. No need for ASCII conversion, fixed record formats, fast streaming and buffering, no read() overhead, etc.
> We can probably get the runtime by grouping a task-clock swcounter > with an appropriate other event.
Would be lovely.
Ingo
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