From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-1168001-1522340041-2-17837750700710123112 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no ("Email failed DMARC policy for domain") X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.249, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='CN', FromHeader='uk', MailFrom='org' X-Spam-charsets: plain='UTF-8' X-IgnoreVacation: yes ("Email failed DMARC policy for domain") X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=fm2; t= 1522340040; b=vh7J9LPqRrJZuYLSDHaUBqH5odNvk1LfkDJ32llIDrYm24tEE7 S8BrixTYehpnMbX4VpkHNR9lgViEnTt1czSL+5gIiYAF1b1mzpvgYU/E5IA4VQeY FlBD82Oka2pQveN2e/nGNwBZDDPMqIjWEHFh1MdKVyuyAX7eE9vStTbXTN/xflfY OO0hxyr1g4qteWo2upKZsXEGS8GyjV7Thn1vWBxZdOLeCkjOjODDfver0E8cuZlR hlPeNkhK1ykqKNol4l81RoReeYANEMjKPOaRi1O/xKfFkAmH1xOJJPOHPjPpitQj UJpPbIXJ8s1tQAYUN/iaWjjB9clyTkpx9pcA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=message-id:subject:from:to:cc:date :in-reply-to:references:content-type:mime-version :content-transfer-encoding:sender:list-id; s=fm2; t=1522340040; bh=eMAUFiEADnPj6J4ZZptR2OfIOD6mhRcrBOsZ7YhjnaM=; b=J2At6QXS7dSC 2EEYEIfbQtjTJrKRzTDMcY67edxJAGKaBZOsuowxgFdkBL5aDFb8G9UoGUgNw6xV 6awDCnGr7fKsxBo4YUlZtPRErkIfaZX5VWaRaaMSfYGYu62feVduiCMICteg9wOV kCKSXcLZWcH+xjwP//HkBTV8txZ5vmf9wg3PSb1pXU+q1Jzm8j2gd3K54dqI/j6e QqMKdC4jlf0dIXtqO6QSxJ4Q8HPcmsSXivbPk/BAYA123sMrMQ3sj/sra4RJvByb CTRO59nj3cK8LpyY/fjtmuhiswj3fjizG56O08I7pSWaIxEGqqMIztS+nTMyliqm pGZlRfatRw== ARC-Authentication-Results: i=1; mx1.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,has-list-id=yes,d=none) header.from=codethink.co.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-cm=none score=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=codethink.co.uk header.result=pass header_is_org_domain=yes; x-vs=clean score=-100 state=0 Authentication-Results: mx1.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,has-list-id=yes,d=none) header.from=codethink.co.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-cm=none score=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=codethink.co.uk header.result=pass header_is_org_domain=yes; x-vs=clean score=-100 state=0 X-ME-VSCategory: clean X-CM-Envelope: MS4wfH9vCY39n6CvCcTHPn5Xpm27oB3pcgMeqOBLECZOR+KqrJnmt++m03GME+curqjBnf4+Dil2RhBK0axsd1bvp6nkr1w3Kqwxz5fsOOdOeJA+iF8mjHr+ FM9CEr5bpMzbb5MG2tkhvjOSIcorsfdOouezY1fn4tvaDrBdZ6qwqChCwcqOcn5hx4jCnOh9xomwcz3/wtEzg6KHU04Ai0rChaaU5VMNp0oQ5LcN3ULYYp62 X-CM-Analysis: v=2.3 cv=WaUilXpX c=1 sm=1 tr=0 a=UK1r566ZdBxH71SXbqIOeA==:117 a=UK1r566ZdBxH71SXbqIOeA==:17 a=IkcTkHD0fZMA:10 a=v2DPQv5-lfwA:10 a=1XWaLZrsAAAA:8 a=Lyni5Ml3Mjy5FSvaWBsA:9 a=QEXdDO2ut3YA:10 X-ME-CMScore: 0 X-ME-CMCategory: none Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751714AbeC2QN7 (ORCPT ); Thu, 29 Mar 2018 12:13:59 -0400 Received: from imap1.codethink.co.uk ([176.9.8.82]:43532 "EHLO imap1.codethink.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751223AbeC2QN6 (ORCPT ); Thu, 29 Mar 2018 12:13:58 -0400 Message-ID: <1522340036.2654.20.camel@codethink.co.uk> Subject: Re: [PATCH 4.4 014/134] perf tools: Make perf_event__synthesize_mmap_events() scale From: Ben Hutchings To: Greg Kroah-Hartman , linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org, Stephane Eranian , Jiri Olsa , Andy Lutomirski , Namhyung Kim , Peter Zijlstra , Arnaldo Carvalho de Melo , Sasha Levin Date: Thu, 29 Mar 2018 17:13:56 +0100 In-Reply-To: <20180319171851.147448695@linuxfoundation.org> References: <20180319171849.024066323@linuxfoundation.org> <20180319171851.147448695@linuxfoundation.org> Organization: Codethink Ltd. Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6-1+deb9u1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Mon, 2018-03-19 at 19:04 +0100, Greg Kroah-Hartman wrote: > 4.4-stable review patch.  If anyone has any objections, please let me know. > > ------------------ > > From: Stephane Eranian > > > [ Upstream commit 88b897a30c525c2eee6e7f16e1e8d0f18830845e ] > > This patch significantly improves the execution time of > perf_event__synthesize_mmap_events() when running perf record on systems > where processes have lots of threads. > > It just happens that cat /proc/pid/maps support uses a O(N^2) algorithm to > generate each map line in the maps file.  If you have 1000 threads, then you > have necessarily 1000 stacks.  For each vma, you need to check if it > corresponds to a thread's stack.  With a large number of threads, this can take > a very long time. I have seen latencies >> 10mn. > > As of today, perf does not use the fact that a mapping is a stack, therefore we > can work around the issue by using /proc/pid/tasks/pid/maps.  This entry does > not try to map a vma to stack and is thus much faster with no loss of > functonality. > > The proc-map-timeout logic is kept in case users still want some upper limit. > > In V2, we fix the file path from /proc/pid/tasks/pid/maps to actual > /proc/pid/task/pid/maps, tasks -> task.  Thanks Arnaldo for catching this. > > Committer note: > > This problem seems to have been elliminated in the kernel since commit : > b18cb64ead40 ("fs/proc: Stop trying to report thread stacks"). [...] I don't think so. It looks like this was fixed by commit 65376df58217 ("proc: revert /proc//maps [stack:TID] annotation") which we already have in 4.4-stable. But older branches (3.16, 3.18, 4.1) don't have that and probably should do. It looks like commit b18cb64ead40 ("fs/proc: Stop trying to report thread stacks") is also a candidate for stable. Ben. -- Ben Hutchings Software Developer, Codethink Ltd.