linux-kernel - Re: [PATCH V3 0/6] event synthesization multithreading for perf record

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Date:   Wed, 25 Oct 2017 11:02:02 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        "Liang, Kan" <kan.liang@...el.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "jolsa@...nel.org" <jolsa@...nel.org>,
        "wangnan0@...wei.com" <wangnan0@...wei.com>,
        "hekuang@...wei.com" <hekuang@...wei.com>,
        "alexander.shishkin@...ux.intel.com" 
        <alexander.shishkin@...ux.intel.com>,
        "Hunter, Adrian" <adrian.hunter@...el.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>, kernel-team@....com
Subject: Re: [PATCH V3 0/6] event synthesization multithreading for perf
 record

On Wed, Oct 25, 2017 at 11:35:39AM +0900, Namhyung Kim wrote:
> Hi Ingo,
> 
> On Tue, Oct 24, 2017 at 03:25:23PM +0200, Ingo Molnar wrote:
> > 
> > * Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
> > 
> > > Em Tue, Oct 24, 2017 at 02:59:44PM +0200, Ingo Molnar escreveu:
> > > > 
> > > > * Jiri Olsa <jolsa@...hat.com> wrote:
> > > > 
> > > > > I recently made some changes on threaded record, which are based
> > > > > on Namhyungs time* API, which is needed to read/sort the data afterwards
> > > > > 
> > > > > but I wasn't able to get any substantial and constant reduce of LOST events
> > > > > and then I got sidetracked and did not finish, but it's in here:
> > > > 
> > > > So, in the context of system-wide profiling, the way that would work best I think 
> > > > is the following:
> > > > 
> > > >   thread #0 binds itself to CPU#0 (via sched_setaffinity) and creates a per-CPU event on CPU#0
> > > >   thread #1 binds itself to CPU#1 (via sched_setaffinity) and creates a per-CPU event on CPU#1
> > > >   thread #2 binds itself to CPU#2 (via sched_setaffinity) and creates a per-CPU event on CPU#2
> > > 
> > > Right, that is how I think it should be done as well, and those will
> > > just dump on separate files, in a per session directory, with an extra
> > > file for the session details, in what is now the header.
> > 
> > Yes. Also note how easy to examine such a directory structure is - I'd suggest 
> > making all the session details textual eventually. I.e. only the ring-buffers 
> > should be binary, the rest should be arch-independent text encoding.
> > 
> > It's also very extensible.
> 
> Agreed.
> 
> Also for multithread work, conversion to directory should be the first
> step IMHO.

yes, but thats what we already have with yours (Namhyung's) HEADER_DATA_INDEX

jirka