From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 549C3CA9EAD for ; Sun, 20 Oct 2019 16:14:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 30212222C2 for ; Sun, 20 Oct 2019 16:14:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726575AbfJTQN7 (ORCPT ); Sun, 20 Oct 2019 12:13:59 -0400 Received: from mga17.intel.com ([192.55.52.151]:25889 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726383AbfJTQN7 (ORCPT ); Sun, 20 Oct 2019 12:13:59 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 20 Oct 2019 09:13:58 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,320,1566889200"; d="scan'208";a="195909354" Received: from tassilo.jf.intel.com (HELO tassilo.localdomain) ([10.7.201.137]) by fmsmga008.fm.intel.com with ESMTP; 20 Oct 2019 09:13:58 -0700 Received: by tassilo.localdomain (Postfix, from userid 1000) id 229A43002BE; Sun, 20 Oct 2019 09:13:58 -0700 (PDT) From: Andi Kleen To: acme@kernel.org Cc: jolsa@kernel.org, eranian@google.com, kan.liang@linux.intel.com, peterz@infradead.org, linux-kernel@vger.kernel.org Subject: Optimize perf stat for large number of events/cpus v1 Date: Sun, 20 Oct 2019 09:13:37 -0700 Message-Id: <20191020161346.18938-1-andi@firstfloor.org> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch kit optimizes perf stat for a large number of events on systems with many CPUs and PMUs. Some profiling shows that the most overhead is doing IPIs to all the target CPUs. We can optimize this by using sched_setaffinity to set the affinity to a target CPU once and then doing the perf operation for all events on that CPU. This requires some restructuring, but cuts the set up time quite a bit. In theory we could go further by parallelizing these setups too, but that would be much more complicated and for now just batching it per CPU seems to be sufficient. At some point with many more cores parallelization or a better bulk perf setup API might be needed though. In addition perf does a lot of redundant /sys accesses with many PMUs, which can be also expensve. This is also optimized. On a large test case (>700 events with many weak groups) on a 94 CPU system I go from real 0m8.607s user 0m0.550s sys 0m8.041s to real 0m3.269s user 0m0.760s sys 0m1.694s so shaving ~6 seconds of system time, at slightly more cost in perf stat itself. On a 4 socket system with the savings are more dramatic: real 0m15.641s user 0m0.873s sys 0m14.729s to real 0m4.493s user 0m1.578s sys 0m2.444s so 11s difference in the user visible set up time. Also available in git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc perf/stat-scale-3 v1: Initial post. -Andi