linux-kernel - Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1)

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Message-ID: <20151210080118.GA8664@gmail.com>
Date:	Thu, 10 Dec 2015 09:01:18 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jiri Olsa <jolsa@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	Stephane Eranian <eranian@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1)


* Namhyung Kim <namhyung@...nel.org> wrote:

> Hello,
> 
> This patchset if an attempt to support multi-threading in perf top.
> In fact, perf top already run on two threads - a worker thread and a
> display thread.  However processing all samples with a single thread
> in a large machine can have scalability problems.
> 
> This patchset extends it to have multiple worker threads to process
> samples concurrently.  Users can control the number of threads using
>  --num-thread option.  And there's a collector thread for passing hist
> entries from worker threads to the display thread.

Could you please make the number of threads default to the number of CPUs?

Since perf top is doing one perf event per CPU anyway, that's a pretty natural 
model.

( I think 'perf record' should use per CPU threads as well to receive events, to 
  address the 'IO overload' problems with -g recording on larger CPU counts. )

Thanks,

	Ingo
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