Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752988AbbGMS7j (ORCPT ); Mon, 13 Jul 2015 14:59:39 -0400 Received: from mga02.intel.com ([134.134.136.20]:26656 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752784AbbGMS7h convert rfc822-to-8bit (ORCPT ); Mon, 13 Jul 2015 14:59:37 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.15,464,1432623600"; d="scan'208";a="605412634" From: "Liang, Kan" To: Jiri Olsa CC: "acme@kernel.org" , "jolsa@kernel.org" , "namhyung@kernel.org" , "ak@linux.intel.com" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH RFC V2 3/5] perf,tool: partial time support Thread-Topic: [PATCH RFC V2 3/5] perf,tool: partial time support Thread-Index: AQHQuNr/GuWHy9rzOUybnSiXGgamC53XU8OAgAJcI1A= Date: Mon, 13 Jul 2015 18:59:17 +0000 Message-ID: <37D7C6CF3E00A74B8858931C1DB2F0770188BEDF@SHSMSX103.ccr.corp.intel.com> References: <1436264345-12085-1-git-send-email-kan.liang@intel.com> <1436264345-12085-4-git-send-email-kan.liang@intel.com> <20150712132225.GA1687@krava.redhat.com> In-Reply-To: <20150712132225.GA1687@krava.redhat.com> Accept-Language: zh-CN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1917 Lines: 46 > -----Original Message----- > From: Jiri Olsa [mailto:jolsa@redhat.com] > Sent: Sunday, July 12, 2015 9:22 AM > To: Liang, Kan > Cc: acme@kernel.org; jolsa@kernel.org; namhyung@kernel.org; > ak@linux.intel.com; linux-kernel@vger.kernel.org > Subject: Re: [PATCH RFC V2 3/5] perf,tool: partial time support > > On Tue, Jul 07, 2015 at 06:19:03AM -0400, kan.liang@intel.com wrote: > > From: Kan Liang > > > > When multiple events are sampled it may not be needed to collect fine > > grained time stamps on all events. The sample sites are usually nearby. > > It's enough to have time stamps on the regular reference events. > > This patchkit adds the ability to turn off time stamps per event. This > > in term can reduce sampling overhead and the size of the perf.data. > > how is this usable in some perf example? I dont get the correlation > between 'refference' and the rest of the events in the report time.. > One usable case of partial time is to work with partial callgraph to enable "PEBS threshold > 1" (https://lkml.org/lkml/2015/5/10/196), which can significantly reduce the sampling overhead. For the case as above, we intend to get callgraph in large PEBS threshold. Timestamp is not that important. So I didn't correlate the reference event and the rest events here. But it's doable. We can use oe->last_flush to set the rest events' time. The only problem is that I cannot find a useable partial time only case. (Partial time itself cannot save as much as partial callgraph) So I think we do not need to implement such correlation. I guess I will keep the code unchanged, but correct the description. Is it OK? Thanks, Kan -- 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/