linux-kernel - Re: [PATCH 3/3] perf events: add timehist option to record and report

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Message-ID: <20110218192953.GB5658@nowhere>
Date:	Fri, 18 Feb 2011 20:29:56 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Cc:	David Ahern <daahern@...co.com>, Ingo Molnar <mingo@...e.hu>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	peterz@...radead.org, paulus@...ba.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 3/3] perf events: add timehist option to record and
 report

On Fri, Feb 18, 2011 at 04:41:19PM -0200, Arnaldo Carvalho de Melo wrote:
> Em Fri, Feb 18, 2011 at 06:59:30PM +0100, Frederic Weisbecker escreveu:
> >   sched:sched_wait_task                      [Tracepoint event]
> >   sched:sched_wakeup                         [Tracepoint event]
> >   sched:sched_wakeup_new                     [Tracepoint event]
> >   sched:sched_switch                         [Tracepoint event]
> >   sched:sched_migrate_task                   [Tracepoint event]
> >   sched:sched_process_free                   [Tracepoint event]
> >   sched:sched_process_exit                   [Tracepoint event]
> > 
> > 
> > You have the sched:sched_switch event and many others.
> > 
> > Just try:
> > 
> > perf record -a -e sched:*
> > perf script
> > 
> >             perf-4128  [000] 19242.870025: sched_stat_runtime: comm=perf pid=4128 runtime=7430405 [ns] vruntime=3530192223488 
> >             perf-4128  [000] 19242.870042: sched_stat_runtime: comm=perf pid=4128 runtime=23142 [ns] vruntime=3530192246630 [n
> >             perf-4128  [000] 19242.870045: sched_stat_sleep: comm=kondemand/0 pid=59 delay=9979163 [ns]
> >             perf-4128  [000] 19242.870048: sched_wakeup: comm=kondemand/0 pid=59 prio=120 success=1 target_cpu=000
> >             perf-4128  [000] 19242.870063: sched_stat_runtime: comm=perf pid=4128 runtime=21581 [ns] vruntime=3530192268211 [n
> >             perf-4128  [000] 19242.870066: sched_stat_wait: comm=kondemand/0 pid=59 delay=21581 [ns]
> >             perf-4128  [000] 19242.870069: sched_switch: prev_comm=perf prev_pid=4128 prev_prio=120 prev_state=R ==> next_comm
> >      kondemand/0-59    [000] 19242.870091: sched_stat_runtime: comm=kondemand/0 pid=59 runtime=27362 [ns] vruntime=35301862739
> >      kondemand/0-59    [000] 19242.870094: sched_stat_wait: comm=perf pid=4128 delay=27362 [ns]
> >      kondemand/0-59    [000] 19242.870095: sched_switch: prev_comm=kondemand/0 prev_pid=59 prev_prio=120 prev_state=S ==> next
> > 
> > And you can run your own script on these events:
> > 
> > $ sudo ./perf script -g python
> > generated Python script: perf-script.py
> > 
> > Edit perf-script.py and then run it:
> > 
> > $ perf script -s ./perf-script.py
> > 
> > That also works for perl.
> > 
> > The timestamps will be the cpu time and not the walltime, but at least that seems
> > to be partly what you seek?
> 
> The whole issue for him, AFAIK, is to correlate perf events with app
> events.
> 
> Think about tcpdump + networking tracepoints or 'perf probe' dynamic
> events in the network stack, he wants to merge those logs and correlate
> the tcpdump packet exchange with the tracepoints events in the network
> stack, etc.
> 
> I.e. it doesn't matter if it is ftrace or not, having a common clock
> shared between apps and kernel tracing/whatever infrastructure is what
> David is after, right?
> 
> He can change userspace to use the clock the kernel is using in the
> perf/ftrace/whatever infrastructure or make the kernel use the clock
> userspace uses.
> 
> The issue here is who will bend, u or k ;-)

Right. I don't disagree with the need of a walltime. That already
in debate :)

I was rather arguing about the tracing part. Adding support in perf report
in the wrong way to do this. If something must be extended, It should be done
in perf script, where we do the tracing support.
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