From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756082AbcARR7w (ORCPT ); Mon, 18 Jan 2016 12:59:52 -0500 Received: from outbound-smtp07.blacknight.com ([46.22.139.12]:43895 "EHLO outbound-smtp07.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755919AbcARR7u (ORCPT ); Mon, 18 Jan 2016 12:59:50 -0500 Date: Mon, 18 Jan 2016 17:59:46 +0000 From: Mel Gorman To: Jiri Olsa Cc: Arnaldo Carvalho de Melo , LKML Subject: perf stat stddev reporting broken since "perf stat: Introduce read_counters function" Message-ID: <20160118175946.GC10802@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I noticed that perf stat in 4.4 is not printing stddev figures as expected and bisected it to commit 106a94a0f8c2 ("perf stat: Introduce read_counters function"). # Kernel 4.4 # make clean && make prefix=/usr && ./perf stat -r 5 sleep 1 Performance counter stats for 'sleep 1' (5 runs): 0.466683 task-clock (msec) # 0.000 CPUs utilized 1 context-switches # 0.002 M/sec 1 cpu-migrations # 0.002 M/sec 66 page-faults # 0.144 M/sec 1,630,220 cycles # 3.562 GHz stalled-cycles-frontend stalled-cycles-backend 902,686 instructions # 0.66 insns per cycle 185,692 branches # 405.786 M/sec 8,640 branch-misses # 4.63% of all branches 1.000855883 seconds time elapsed ( +- 0.01% ) # git checkout 106a94a0f8c207ef4113ce7e32f34a00b3b174e7^ Performance counter stats for 'sleep 1' (5 runs): 0.397939 task-clock (msec) # 0.000 CPUs utilized ( +- 3.37% ) 1 context-switches # 0.003 M/sec 0 cpu-migrations # 0.000 K/sec 67 page-faults # 0.169 M/sec ( +- 0.56% ) 1,360,763 cycles # 3.420 GHz ( +- 2.14% ) stalled-cycles-frontend stalled-cycles-backend 903,901 instructions # 0.66 insns per cycle ( +- 0.24% ) 186,472 branches # 468.595 M/sec ( +- 0.29% ) 8,599 branch-misses # 4.61% of all branches ( +- 0.77% ) 1.000761882 seconds time elapsed ( +- 0.00% ) # git checkout 106a94a0f8c207ef4113ce7e32f34a00b3b174e7 Performance counter stats for 'sleep 1' (5 runs): 0.583178 task-clock (msec) # 0.001 CPUs utilized 1 context-switches # 0.002 M/sec 0 cpu-migrations # 0.000 K/sec 67 page-faults # 0.141 M/sec 1,224,416 cycles # 2.585 GHz stalled-cycles-frontend stalled-cycles-backend 892,568 instructions # 0.68 insns per cycle 184,975 branches # 390.554 M/sec 8,512 branch-misses # 4.57% of all branches 1.000889249 seconds time elapsed ( +- 0.01% ) I checked and current master in Linus' tree is also broken. Is this change in documented perf stat behaviour intentional? -- Mel Gorman SUSE Labs