From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755526AbbCPUs2 (ORCPT ); Mon, 16 Mar 2015 16:48:28 -0400 Received: from mga02.intel.com ([134.134.136.20]:4225 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753183AbbCPUs1 (ORCPT ); Mon, 16 Mar 2015 16:48:27 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.11,411,1422950400"; d="scan'208";a="680967587" Date: Mon, 16 Mar 2015 13:48:26 -0700 From: Andi Kleen To: "Liang, Kan" Cc: Namhyung Kim , "acme@kernel.org" , "linux-kernel@vger.kernel.org" , "eranian@google.com" Subject: Re: [PATCH 1/1] perf, tool: partial callgrap and time support in perf record Message-ID: <20150316204826.GK31334@tassilo.jf.intel.com> References: <1426213087-25593-1-git-send-email-kan.liang@intel.com> <20150316020348.GO943@sejong> <37D7C6CF3E00A74B8858931C1DB2F07701751D32@SHSMSX103.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <37D7C6CF3E00A74B8858931C1DB2F07701751D32@SHSMSX103.ccr.corp.intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 16, 2015 at 08:35:30PM +0000, Liang, Kan wrote: > > > > > > Hi Kan, > > > > On Fri, Mar 13, 2015 at 02:18:07AM +0000, kan.liang@intel.com wrote: > > > From: Kan Liang > > > > > > When multiple events are sampled it may not be needed to collect > > > callgraphs for all of them. The sample sites are usually nearby, and > > > it's enough to collect the callgraphs on a reference event (such as > > > precise cycles or precise instructions). Similarly we also don't need > > > fine grained time stamps on all events, as it's enough to have time > > > stamps on the regular reference events. This patchkit adds the ability > > > to turn off callgraphs and time stamps per event. This in term can > > > reduce sampling overhead and the size of the perf.data (add some data) > > > > Have you taken a look into group sampling feature? > > (e.g. perf record -e '{ev1,ev2}:S') > > > > I didn't find any issues when running group read. > The patch doesn't change the behavior of group read features. > > Did you observe any issues after applying the patch? I think Namhyungs questions was if group read can be used instead to decrease the data size. The answer is no: it solves a different problem. Group read is just fine granuality counting. It cannot be used to sample for multiple events in parallel. -Andi