On Thu, Nov 4, 2021 at 5:17 PM Mel Gorman <mgorman@suse.de> wrote:

> On Thu, Nov 04, 2021 at 02:47:03AM +0800, Jimmy Shiu wrote:
> > trace_sched_blocked_trace in CFS is really useful for debugging via
> > trace because it tell where the process was stuck on callstack.
> >
> > For example,
> >            <...>-6143  ( 6136) [005] d..2    50.278987:
> sched_blocked_reason: pid=6136 iowait=0 caller=SyS_mprotect+0x88/0x208
> >            <...>-6136  ( 6136) [005] d..2    50.278990:
> sched_blocked_reason: pid=6142 iowait=0 caller=do_page_fault+0x1f4/0x3b0
> >            <...>-6142  ( 6136) [006] d..2    50.278996:
> sched_blocked_reason: pid=6144 iowait=0 caller=SyS_prctl+0x52c/0xb58
> >            <...>-6144  ( 6136) [006] d..2    50.279007:
> sched_blocked_reason: pid=6136 iowait=0 caller=vm_mmap_pgoff+0x74/0x104
> >
> > However, sometime it gives pointless information like this.
> >     RenderThread-2322  ( 1805) [006] d.s3    50.319046:
> sched_blocked_reason: pid=6136 iowait=1
> caller=__lock_page_killable+0x17c/0x220
> >      logd.writer-594   (  587) [002] d.s3    50.334011:
> sched_blocked_reason: pid=6126 iowait=1 caller=wait_on_page_bit+0x194/0x208
> >   kworker/u16:13-333   (  333) [007] d.s4    50.343161:
> sched_blocked_reason: pid=6136 iowait=1
> caller=__lock_page_killable+0x17c/0x220
> >
>
> /me peers at coffee
>
> Maybe I'm blind but aside from Matthew's concerns, this
> appears to rely on an Android patch that is not upstream
>
> https://android.googlesource.com/kernel/msm/+/c9f00aa0e25e397533c198a0fcf6246715f99a7b%5E!/

Yes, Mel.
The main purpose is to help get_wchan() to get the meaningful information
of the schedule() caller and can also benefit to Android
sched_blocked_reason trace.
Maybe I should edit the commit message and remove the Android specific logs.
Would that be OK?


>
>
> --
> Mel Gorman
> SUSE Labs
>