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Sat, 3 Mar 2018 17:31:35 -0500 Received: from mail-sn1nam01on0104.outbound.protection.outlook.com ([104.47.32.104]:49722 "EHLO NAM01-SN1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933694AbeCCWb2 (ORCPT ); Sat, 3 Mar 2018 17:31:28 -0500 From: Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" CC: Stephane Eranian , Andy Lutomirski , Namhyung Kim , Peter Zijlstra , Arnaldo Carvalho de Melo , Sasha Levin Subject: [PATCH AUTOSEL for 4.9 028/219] perf tools: Make perf_event__synthesize_mmap_events() scale Thread-Topic: [PATCH AUTOSEL for 4.9 028/219] perf tools: Make perf_event__synthesize_mmap_events() scale Thread-Index: AQHTsz7qFH7IlbHWoE2wAhj8JY6qlg== Date: Sat, 3 Mar 2018 22:28:12 +0000 Message-ID: <20180303222716.26640-28-alexander.levin@microsoft.com> References: <20180303222716.26640-1-alexander.levin@microsoft.com> In-Reply-To: <20180303222716.26640-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;MW2PR2101MB0970;7:4p9PqEFWSxISgz8I8uY/IXE20Jlow72/peT15zHiC12IzTRQFsV8eJJnZ34PJkDOAcbAp/4p5e3ALKTgKRbjjREMo1ddgHho/vrpCQjeiNPUOQ71wJng7nmcbrli9JoTybqKQ0hKR/8UYCVAU0mTrrpv8uMDb9ZTh+9V9f9MTJrGJezkZQ/x9bDuZvS97/NhuovGeHcKKP8u4H0p9TuXMCAU2lMsl8zd+OwDtVsXU7vypF/bgvHgTh8V/wDe8CHs x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: feaceb55-7cdd-462e-51b1-08d581567dec x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(4534165)(4627221)(201703031133081)(201702281549075)(48565401081)(5600026)(4604075)(3008032)(2017052603307)(7193020);SRVR:MW2PR2101MB0970; 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x-microsoft-antispam-message-info: DRdYne2D2IQT+KOZQMXv1g8o5Aepb4so2yT2cJO5azF0Eb1RvbgOCXMhHSV9SDPNLrehSB1WkhM6GlAu2cp4ovZq6ueSPfdrGDyVKvoQrhNRm7TS1LroHcxH7QHiCQR/Tp/iAuBPweOJAiCgQt3A+2uTPHi3kVipm2bXqOaryoY= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: feaceb55-7cdd-462e-51b1-08d581567dec X-MS-Exchange-CrossTenant-originalarrivaltime: 03 Mar 2018 22:28:12.1037 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR2101MB0970 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: 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 yo= u 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, therefor= e we can work around the issue by using /proc/pid/tasks/pid/maps. This entry do= es 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 limi= t. 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"). Signed-off-by: Stephane Eranian Acked-by: Jiri Olsa Cc: Andy Lutomirski Cc: Namhyung Kim Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20170315135059.GC2177@redhat.com Link: http://lkml.kernel.org/r/1489598233-25586-1-git-send-email-eranian@go= ogle.com Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Sasha Levin --- tools/perf/util/event.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c index 8ab0d7da956b..663192395780 100644 --- a/tools/perf/util/event.c +++ b/tools/perf/util/event.c @@ -255,8 +255,8 @@ int perf_event__synthesize_mmap_events(struct perf_tool= *tool, if (machine__is_default_guest(machine)) return 0; =20 - snprintf(filename, sizeof(filename), "%s/proc/%d/maps", - machine->root_dir, pid); + snprintf(filename, sizeof(filename), "%s/proc/%d/task/%d/maps", + machine->root_dir, pid, pid); =20 fp =3D fopen(filename, "r"); if (fp =3D=3D NULL) { --=20 2.14.1