linux-kernel - RE: [PATCH RFC V2 00/10] perf top optimization

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Date:   Mon, 18 Sep 2017 16:21:47 +0000
From:   "Liang, Kan" <kan.liang@...el.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>
CC:     "peterz@...radead.org" <peterz@...radead.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jolsa@...nel.org" <jolsa@...nel.org>,
        "namhyung@...nel.org" <namhyung@...nel.org>,
        "Hunter, Adrian" <adrian.hunter@...el.com>,
        "Odzioba, Lukasz" <lukasz.odzioba@...el.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>
Subject: RE: [PATCH RFC V2 00/10] perf top optimization



> Em Mon, Sep 18, 2017 at 10:57:08AM +0200, Jiri Olsa escreveu:
> > On Sun, Sep 10, 2017 at 07:23:13PM -0700, kan.liang@...el.com wrote:
> > > From: Kan Liang <kan.liang@...el.com>
> > >
> > > The patch series intends to fix the severe performance issue in
> > > Knights Landing/Mill, when monitoring in heavy load system.
> > > perf top costs a few minutes to show the result, which is
> > > unacceptable.
> > > With the patch series applied, the latency will reduces to several
> > > seconds.
> > >
> > > machine__synthesize_threads and perf_top__mmap_read costs most of
> > > the perf top time (> 99%).
> >
> > looks like this patchset adds locking into code paths used by other
> > single threaded tools and that might be bad for them as noted by Andi
> > in here:
> >
> >   https://marc.info/?l=linux-kernel&m=149031672928989&w=2
> >
> > he proposed solution and it was changed&posted by Arnaldo in here:
> >
> >   https://marc.info/?l=linux-kernel&m=149132267410294&w=2
> >
> > but looks like it never got merged
> >
> > could you please add this or similar code before you add the locking
> > code/overhead in?
> 
> I'm rehashing that patch and adding it on top of what is in my perf/core
> branch, will push soon, for now you can take a look at tmp.perf/core.

Thanks.
I will make the V3 based on tmp.perf/core.

Kan