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

From	Namhyung Kim <namhyung@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1)
Date	2015-12-14 18:20 +0100
Message-ID	<qFEX0-DM-13@gated-at.bofh.it> (permalink)
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On Mon, Dec 14, 2015 at 05:56:14PM +0100, Peter Zijlstra wrote:
> On Tue, Dec 15, 2015 at 01:38:30AM +0900, Namhyung Kim wrote:
> > It requires many changes, but basically I also like the split-up since
> > it's easier to deal with.  IIRC there was an opinion (Andi?) regarding
> > single-file vs multi-file.  The file access will be better for single
> > file so I changed my earlier implementation to use indexed single data
> > file instead of multiple files.
> 
> The page-cache has a lock per inode, so by having all CPUs populate the
> one file you get contention on that.
> 
> Also, I suppose you'll have to arbitrate ranges in that file for each
> cpu to make it work, that too could get you some contention.
> 
> Having a file per cpu avoids all that.

Right.  Now I recall that it was about *report* (not record) time
accessing single file vs. multi files.

At record time we should use file per cpu.  I combined them into
one with index at post-processing time in my earlier work.

Thanks for clarification!
Namhyung
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Thread

Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1) Peter Zijlstra <peterz@infradead.org> - 2015-12-14 10:30 +0100
  Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1) Ingo Molnar <mingo@kernel.org> - 2015-12-14 10:40 +0100
    Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1) David Ahern <dsahern@gmail.com> - 2015-12-14 16:00 +0100
      Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1) Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-12-14 17:30 +0100
        Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1) Peter Zijlstra <peterz@infradead.org> - 2015-12-14 17:50 +0100
          Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1) Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-12-14 19:00 +0100
    Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1) Namhyung Kim <namhyung@kernel.org> - 2015-12-14 17:40 +0100
      Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1) Peter Zijlstra <peterz@infradead.org> - 2015-12-14 18:00 +0100
        Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1) Namhyung Kim <namhyung@kernel.org> - 2015-12-14 18:20 +0100
  Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1) David Ahern <dsahern@gmail.com> - 2015-12-14 15:50 +0100
    Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1) Namhyung Kim <namhyung@kernel.org> - 2015-12-14 18:10 +0100
      Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1) Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-12-14 19:00 +0100
  Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1) Namhyung Kim <namhyung@kernel.org> - 2015-12-14 17:30 +0100
    Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1) Peter Zijlstra <peterz@infradead.org> - 2015-12-14 17:50 +0100

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