Date: Tue, 15 Dec 2015 01:25:35 +0900
From: Namhyung Kim <namhyung@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: David Ahern <dsahern@gmail.com>, Ingo Molnar <mingo@kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Andi Kleen <andi@firstfloor.org>,
        Stephane Eranian <eranian@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>
Subject: Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1)
Message-ID: <20151214162535.GA23614@danjae.kornet>
References: <1449734015-9148-1-git-send-email-namhyung@kernel.org>
 <20151210080118.GA8664@gmail.com>
 <5E6F0F13-9696-45F1-A0E8-CA0B95020D10@gmail.com>
 <20151211081141.GA21600@gmail.com>
 <566AE54B.1010702@gmail.com>
 <20151214092613.GL6357@twins.programming.kicks-ass.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <20151214092613.GL6357@twins.programming.kicks-ass.net>
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1829
Lines: 49

Hi Peter,

On Mon, Dec 14, 2015 at 10:26:13AM +0100, Peter Zijlstra wrote:
> On Fri, Dec 11, 2015 at 08:01:31AM -0700, David Ahern wrote:
> > On 12/11/15 1:11 AM, Ingo Molnar wrote:
> > >
> > >* Namhyung Kim <namhyung@gmail.com> wrote:
> > >
> > >>IIRC David said that thread per cpu seems too much especially on a large system
> > >>(like ~1024 cpu). [...]
> > >
> > >Too much in what fashion? For recording I think it's the fastest, most natural
> > >model - anything else will create cache line bounces.
> > 
> > The intrusiveness of perf on the system under observation. I understand
> > there are a lot of factors that go into it.
> 
> So I can see some of that, if every cpu has its own thread then every
> cpu will occasionally schedule that thread. Whereas if there were less,
> you'd not have that.
> 
> Still, I think it makes sense to implement it, we need the multi-file
> option anyway. Once we have that, we can also implement a per-node
> option, which should be a fairly simple hybrid of the two approaches.
> 
> The thing is, perf-record is really struggling on big machines.

Yes, but perf-record and perf-top is different.  The perf-record
merely saves the data into file while perf-top read events and process
them at the same time without file.  So we should choose different
default IMHO.

I want to focus on perf-top for now, once it's in a good shape, I'll
work on perf record/report too.


> 
> And in an unrelated note, I absolutely detest --buildid being the
> default, it makes perf-record blow chunks.

Maybe we can add a config option?

Thanks,
Namhyung
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/