From: "Liang, Kan" <kan.liang@intel.com>
To: Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@redhat.com>
CC: "peterz@infradead.org" <peterz@infradead.org>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "jolsa@kernel.org" <jolsa@kernel.org>,
        "namhyung@kernel.org" <namhyung@kernel.org>,
        "Hunter, Adrian" <adrian.hunter@intel.com>,
        "Odzioba, Lukasz" <lukasz.odzioba@intel.com>,
        "ak@linux.intel.com" <ak@linux.intel.com>
Subject: RE: [PATCH RFC V2 00/10] perf top optimization
Thread-Topic: [PATCH RFC V2 00/10] perf top optimization
Thread-Index: AQHTKqUGKqa3XFGJ30eMjpDMlJ7smaK53NAAgABEIwCAAL2ZEA==
Date: Mon, 18 Sep 2017 16:21:47 +0000
Message-ID: <37D7C6CF3E00A74B8858931C1DB2F077537C38AF@SHSMSX103.ccr.corp.intel.com>
References: <1505096603-215017-1-git-send-email-kan.liang@intel.com>
 <20170918085708.GC17203@krava> <20170918130100.GF14469@kernel.org>
In-Reply-To: <20170918130100.GF14469@kernel.org>
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> 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@intel.com wrote:
> > > From: Kan Liang <kan.liang@intel.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