linux-kernel - Re: [tip:perf/core] perf tools: Allow multiple threads or processes in record, stat, top

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Date:	Fri, 02 Mar 2012 07:21:56 -0700
From:	David Ahern <dsahern@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	mingo@...hat.com, hpa@...or.com, paulus@...ba.org,
	linux-kernel@...r.kernel.org, acme@...hat.com, fweisbec@...il.com,
	peterz@...radead.org, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [tip:perf/core] perf tools: Allow multiple threads or processes
 in record, stat, top

On 3/2/12 3:56 AM, Ingo Molnar wrote:
> I have a bigger NUMA testbox where perf sampling (perf top, perf
> record, etc.) stopped working (perf stat is fine), and I've
> bisected it back to the above commit.
>
>   b52956c961be3a04182ae7b776623531601e0fb7 is the first bad commit
>
> Checking out eca1c3e3f937 works fine, b52956c961b is broken,
> repeatedly - so the bisection is reliable.
>
> One symptom is no sampling records in the perf.data:
>
> phoenix:~>  perf record -a sleep 1
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.023 MB perf.data (~988 samples) ]
> phoenix:~>  perf report --stdio
> Warning:
> The perf.data file has no samples!
> # ========
> # captured on: Fri Mar  2 12:01:41 2012
> # hostname : phoenix
> # os release : 3.3.0-rc5+
> # perf version : 3.3.rc5.1698.g68a63a.dirty
> # arch : x86_64
> # nrcpus online : 16
> # nrcpus avail : 16
> # cpudesc : Quad-Core AMD Opteron(tm) Processor 8356
> # cpuid : AuthenticAMD,16,2,3
> # total memory : 33012240 kB
> # cmdline : /home/mingo/bin/perf record -a sleep 1
> # event : name = cycles, type = 0, config = 0x0, config1 = 0x0, config2 = 0x0, excl_usr = 0, excl_k
> # HEADER_CPU_TOPOLOGY info available, use -I to display
> # HEADER_NUMA_TOPOLOGY info available, use -I to display
> # ========
> phoenix:~>  perf --version
> perf version 3.3.rc5.1698.g68a63a.dirty
> phoenix:~>
>
> The later fixes to b52956c9, such as:
>
>    6b1bee9035d4: perf tools: fix broken perf record -a mode
>
> did not fix this system - it's still broken as of today's -tip.
>
> Another system running the same kernel does not exhibit this
> problem, so it's somehow specific to this system.
>
> I have not looked deep into this, let me know if you need more
> data.
>
> Thanks,
>
> 	Ingo


Ok. I have a similar Intel based box - 2 socket, E5540 with 24G; this is 
the box I typically use for testing. I'll take a look at this later 
today and see what I can find.

David

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