Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753921AbbFMPAP (ORCPT ); Sat, 13 Jun 2015 11:00:15 -0400 Received: from mga14.intel.com ([192.55.52.115]:33296 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753008AbbFMPAJ convert rfc822-to-8bit (ORCPT ); Sat, 13 Jun 2015 11:00:09 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,608,1427785200"; d="scan'208";a="587211830" From: "Liang, Kan" To: David Ahern , Andi Kleen CC: Arnaldo Carvalho de Melo , "linux-kernel@vger.kernel.org" , "Huang, Ying" Subject: RE: [PATCH 1/1] perf,tools: add time out to force stop endless mmap processing Thread-Topic: [PATCH 1/1] perf,tools: add time out to force stop endless mmap processing Thread-Index: AQHQo44i3glIe3h0sEG/9i/L0QJfWp2m0lUAgAAU7wCAADmvgIAAYMUAgAFtkPD//5AIgIAAk2vg//+KeQCAAJJsMP//j0eAABDMbwD//5DlgP//ah+AgAEPfQD//tt/MA== Date: Sat, 13 Jun 2015 14:59:56 +0000 Message-ID: <37D7C6CF3E00A74B8858931C1DB2F07701876ECA@SHSMSX103.ccr.corp.intel.com> References: <1433922364-22580-1-git-send-email-kan.liang@intel.com> <20150611140614.GC2696@kernel.org> <5579A766.4010504@gmail.com> <20150611184737.GU19417@two.firstfloor.org> <557A28F6.8040603@gmail.com> <37D7C6CF3E00A74B8858931C1DB2F077018767AD@SHSMSX103.ccr.corp.intel.com> <557AFDB1.7030902@gmail.com> <37D7C6CF3E00A74B8858931C1DB2F07701876834@SHSMSX103.ccr.corp.intel.com> <557B16C4.7000000@gmail.com> <37D7C6CF3E00A74B8858931C1DB2F07701876CB2@SHSMSX103.ccr.corp.intel.com> <557B3309.4080002@gmail.com> <37D7C6CF3E00A74B8858931C1DB2F07701876D60@SHSMSX103.ccr.corp.intel.com> <557B4691.7090304@gmail.com> <37D7C6CF3E00A74B8858931C1DB2F07701876DE9@SHSMSX103.ccr.corp.intel.com> <557BAC94.3090301@gmail.com> In-Reply-To: <557BAC94.3090301@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 Content-Length: 1609 Lines: 45 > > > The maps information is not critical for sampling. > > But is for correlating the addresses in those samples. We still have the maps information for other threads in system. Only part of the information for some thread is lost. > > > > > If task_diag does not solve this problem, I think we still need a time > > out to force stop endless mmap processing. It's the simplest working > > solution so far. > > I disagree with the timeout. For example an overloaded system where > perf is not getting scheduled could trigger the same. It's not a perfect solution for all tools. But a working solution for perf. Without timeout, we get nothing from perf top/record. With timeout, we can do sampling. We can correlate the addresses in most samples. It's better than nothing. > > Also, in the spirit of perf if you are going to drop information you need to > generate an event that says information was lost and have the analysis > tools show a message that information was lost. You can't simply bail out > and have "[unknown]" shown for symbols / dsos. I get tons of user > comments about perf showing callchains properly; the proposed patch just > adds to that confusion. Currently, it will print a warning in perf top/record. I think I can do more and print warning in perf_session__warn_about_errors as Arnaldo suggested. Thanks, Kan > > David -- 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/