Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754601AbdIRNBE (ORCPT ); Mon, 18 Sep 2017 09:01:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:35712 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751747AbdIRNBD (ORCPT ); Mon, 18 Sep 2017 09:01:03 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A9D7321C9B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=acme@kernel.org Date: Mon, 18 Sep 2017 10:01:00 -0300 From: Arnaldo Carvalho de Melo To: Jiri Olsa Cc: kan.liang@intel.com, peterz@infradead.org, mingo@redhat.com, linux-kernel@vger.kernel.org, jolsa@kernel.org, namhyung@kernel.org, adrian.hunter@intel.com, lukasz.odzioba@intel.com, ak@linux.intel.com Subject: Re: [PATCH RFC V2 00/10] perf top optimization Message-ID: <20170918130100.GF14469@kernel.org> References: <1505096603-215017-1-git-send-email-kan.liang@intel.com> <20170918085708.GC17203@krava> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170918085708.GC17203@krava> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1225 Lines: 33 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 > > > > 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. - Arnaldo