From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757746AbbFQRUH (ORCPT ); Wed, 17 Jun 2015 13:20:07 -0400 Received: from mga01.intel.com ([192.55.52.88]:47402 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756504AbbFQRT5 convert rfc822-to-8bit (ORCPT ); Wed, 17 Jun 2015 13:19:57 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,634,1427785200"; d="scan'208";a="729355179" From: "Liang, Kan" To: David Ahern , "acme@kernel.org" CC: "linux-kernel@vger.kernel.org" , "Huang, Ying" , "andi@firstfloor.org" Subject: RE: [PATCH V3 1/2] perf,tools: add time out to force stop proc map processing Thread-Topic: [PATCH V3 1/2] perf,tools: add time out to force stop proc map processing Thread-Index: AQHQqQ/HYQ1CvORGTkmkFvJUQ3PUI52wVoaAgACWMHA= Date: Wed, 17 Jun 2015 17:19:49 +0000 Message-ID: <37D7C6CF3E00A74B8858931C1DB2F077018794D0@SHSMSX103.ccr.corp.intel.com> References: <1434527812-17051-1-git-send-email-kan.liang@intel.com> <55819AB3.9060308@gmail.com> In-Reply-To: <55819AB3.9060308@gmail.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 > > On 6/17/15 1:56 AM, kan.liang@intel.com wrote: > > diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c index > > 793b150..ac6cf2a 100644 > > --- a/tools/perf/util/event.c > > +++ b/tools/perf/util/event.c > > @@ -213,6 +213,8 @@ static int perf_event__synthesize_fork(struct > perf_tool *tool, > > return 0; > > } > > > > +#define MMAP_TIMEOUT (50 * 1000000ULL) > > + > > How did you determine 50msec is a good time? This seems really low to me > considering the range of platforms supported by perf and various run time > conditions. The default needs to work right on all platforms. > I only test 50ms on my platforms. For all platforms, any recommendation? > Why not have the default be infinity and users who need the feature use > the option provided in patch 2? If we set the default to infinity, the user will get nothing when perf top runs in our case. There will be no warning. How do they know that they should change the time out limit? So I still think we need a finite default value. The problem is what's the number. Thanks, Kan