linux-kernel - Re: [PATCH] perf tool: Fix ppid for synthesized fork events

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Message-ID: <20150324201020.GH199787@redhat.com>
Date:	Tue, 24 Mar 2015 16:10:20 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	David Ahern <dsahern@...il.com>
Cc:	acme@...nel.org, linux-kernel@...r.kernel.org,
	Jiri Olsa <jolsa@...hat.com>, jmario@...hat.com
Subject: Re: [PATCH] perf tool: Fix ppid for synthesized fork events

On Thu, Mar 19, 2015 at 03:06:46PM -0600, David Ahern wrote:
> On 3/19/15 2:56 PM, Don Zickus wrote:
> >On Thu, Mar 19, 2015 at 11:41:15AM -0600, David Ahern wrote:
> >>>363b785f38 added synthesized fork events and set a thread's parent id
> >>>to itself. Since we are already processing/proc/<pid>/status the ppid
> >>>can be determined properly. Make it so.
> >Thanks David.  My tester, Joe, is currently running other tests and then is
> >out until Tuesday.  I will try to provide test feedback by Tuesday or
> >Wednesday if it can wait.
> 
> ok. thanks for the heads up.

Hmm, preliminary tests, show a significant slow down in perf record and perf
report.  I would be against this patch for now.  We will dig into what the
problem is.

Joe is running a specjbb bench with lots of threads in the background and
running:

perf mem record -a -e 'cpu/mem-loads,ldlat=50/pp' -e 'cpu/mem-stores/pp' sleep 10


multiple times to get an average.  And also

perf mem report --stdio

to get that timing average too..

He does this with and without the patch.  The difference is usually over 50%
extra time with the patch for both the record timings and report timings. :-(

Cheers,
Don
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