Re: [PATCH 2/2] sched/debug: add sched_update_nr_running tracepoint

[chengjian (D)]

On 2019/9/4 0:05, Valentin Schneider wrote:
> On 03/09/2019 16:43, Radim KrÄmÃÅ wrote:
> > The paper "The Linux Scheduler: a Decade of Wasted Cores" used several
> > custom data gathering points to better understand what was going on in
> > the scheduler.
> > Red Hat adapted one of them for the tracepoint framework and created a
> > tool to plot a heatmap of nr_running, where the sched_update_nr_running
> > tracepoint is being used for fine grained monitoring of scheduling
> > imbalance.
> > The tool is available from https://github.com/jirvoz/plot-nr-running.
> >
> > The best place for the tracepoints is inside the add/sub_nr_running,
> > which requires some shenanigans to make it work as they are defined
> > inside sched.h.
> > The tracepoints have to be included from sched.h, which means that
> > CREATE_TRACE_POINTS has to be defined for the whole header and this
> > might cause problems if tree-wide headers expose tracepoints in sched.h
> > dependencies, but I'd argue it's the other side's misuse of tracepoints.
> >
> > Moving the import sched.h line lower would require fixes in s390 and ppc
> > headers, because they don't include dependecies properly and expect
> > sched.h to do it, so it is simpler to keep sched.h there and
> > preventively undefine CREATE_TRACE_POINTS right after.
> >
> > Exports of the pelt tracepoints remain because they don't need to be
> > protected by CREATE_TRACE_POINTS and moving them closer would be
> > unsightly.
> Pure trace events are frowned upon in scheduler world, try going with
> trace points. Qais did something very similar recently:
>
> https://lore.kernel.org/lkml/20190604111459.2862-1-qais.yousef@xxxxxxx/
>
> You'll have to implement the associated trace events in a module, which
> lets you define your own event format and doesn't form an ABI :).
>
> .


Hi Radim,


Why not try Chrome Tracing

1--Record trace data, scheduling, irq, etc.
ÂÂÂ You can Produce a JSON file with the format expected by Chrome
ÂÂÂ OR
ÂÂÂ just save the captured data directly as "xxx.html", it can still work.
ÂÂÂ cat /sys/kernel/debug/tracing/trace > trace.html
2--Go to chrome://tracing in Chrome,
3--Click "Load" and open your file, or alternatively drag the file into 
Chrome,
4--Profit!


Systrace (Android System Trace) captures and displays execution times of 
your app's
processes and other Android system processes, fortunately, there are 
some ported
versions for Linux Desktop/Server.

https://github.com/gatieme/systrace



references--
https://www.chromium.org/developers/how-tos/trace-event-profiling-tool
https://www.chromium.org/developers/how-tos/trace-event-profiling-tool/trace-event-reading


Thanks,
ÂÂÂ - Cheng Jian.