Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751251AbaAGO0L (ORCPT ); Tue, 7 Jan 2014 09:26:11 -0500 Received: from mail-ob0-f172.google.com ([209.85.214.172]:64755 "EHLO mail-ob0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750910AbaAGO0H (ORCPT ); Tue, 7 Jan 2014 09:26:07 -0500 MIME-Version: 1.0 In-Reply-To: <20140107132034.GA1079@localhost> References: <20140102061242.GB29352@localhost> <20140104190228.GG16438@laptop.programming.kicks-ass.net> <20140105011423.GB11203@localhost> <20140107132034.GA1079@localhost> Date: Tue, 7 Jan 2014 15:26:06 +0100 Message-ID: Subject: Re: perf-stat changes after "Use hrtimers for event multiplexing" From: Stephane Eranian To: Fengguang Wu Cc: Peter Zijlstra , Ingo Molnar , LKML , lkp Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 7, 2014 at 2:20 PM, Fengguang Wu wrote: > Hi Stephane, > > On Tue, Jan 07, 2014 at 10:52:50AM +0100, Stephane Eranian wrote: >> Hi, >> >> With the hrtitmer patch, you will get more regular multiplexing when >> you have idle cores during your benchmark. >> Without the patch, multiplexing was piggybacked on timer tick. The >> timer tick does not occur when a core is idle >> when using a tickless kernel. Thus, the quality of the results with >> hrtimers should be improved. > In other words, if your measurement was not multiplexing events OR your benchmark did not incur idle time, you should not see any difference with previous kernel with no hrtimer mux. > OK, got it. Thanks for the explanations! > > Thanks, > Fengguang > >> >> On Sun, Jan 5, 2014 at 2:14 AM, Fengguang Wu wrote: >> > On Sat, Jan 04, 2014 at 08:02:28PM +0100, Peter Zijlstra wrote: >> >> On Thu, Jan 02, 2014 at 02:12:42PM +0800, fengguang.wu@intel.com wrote: >> >> > Greetings, >> >> > >> >> > We noticed many perf-stat changes between commit 9e6302056f ("perf: Use >> >> > hrtimers for event multiplexing") and its parent commit ab573844e. >> >> > Are these expected changes? >> >> > >> >> > ab573844e3058ee 9e6302056f8029f438e853432 >> >> > --------------- ------------------------- >> >> > 152917 +842.9% 1441897 TOTAL interrupts.0:IO-APIC-edge.timer >> >> > 545996 +478.0% 3155637 TOTAL interrupts.LOC >> >> > 182281 +12.3% 204718 TOTAL softirqs.SCHED >> >> > 1.986e+08 -96.4% 7105919 TOTAL perf-stat.node-store-misses >> >> > 107241719 -99.7% 317525 TOTAL perf-stat.node-prefetch-misses >> >> > 1.938e+08 -90.7% 17930426 TOTAL perf-stat.node-load-misses >> >> > 2590 +247.8% 9009 TOTAL vmstat.system.in >> >> > 4.549e+12 +158.3% 1.175e+13 TOTAL perf-stat.stalled-cycles-backend >> >> > 6.807e+12 +149.1% 1.696e+13 TOTAL perf-stat.stalled-cycles-frontend >> >> > 1.753e+08 -50.8% 86339289 TOTAL perf-stat.node-prefetches >> >> > 8.326e+11 +45.0% 1.207e+12 TOTAL perf-stat.cpu-cycles >> >> > 37932143 +32.2% 50146025 TOTAL perf-stat.iTLB-load-misses >> >> > 4.738e+11 +30.1% 6.165e+11 TOTAL perf-stat.iTLB-loads >> >> > 2.56e+11 +30.1% 3.33e+11 TOTAL perf-stat.L1-icache-loads >> >> > 4.951e+11 +24.6% 6.169e+11 TOTAL perf-stat.instructions >> >> > 7.85e+08 +7.5% 8.439e+08 TOTAL perf-stat.LLC-prefetch-misses >> >> > 1.891e+12 +22.8% 2.322e+12 TOTAL perf-stat.ref-cycles >> >> > 4.344e+08 -20.3% 3.462e+08 TOTAL perf-stat.node-loads >> >> > 2.836e+11 +17.4% 3.328e+11 TOTAL perf-stat.branch-loads >> >> > 9.506e+10 +24.5% 1.183e+11 TOTAL perf-stat.branch-load-misses >> >> > 2.803e+11 +18.4% 3.319e+11 TOTAL perf-stat.branch-instructions >> >> > 7.988e+10 +20.9% 9.658e+10 TOTAL perf-stat.bus-cycles >> >> > 2.041e+09 +22.2% 2.495e+09 TOTAL perf-stat.branch-misses >> >> > 229145 -17.3% 189601 TOTAL perf-stat.cpu-migrations >> >> > 1.782e+11 +17.9% 2.1e+11 TOTAL perf-stat.dTLB-loads >> >> > 4.702e+08 -14.8% 4.006e+08 TOTAL perf-stat.LLC-load-misses >> >> > 1.418e+11 +17.4% 1.666e+11 TOTAL perf-stat.L1-dcache-loads >> >> > 1.838e+09 +16.1% 2.133e+09 TOTAL perf-stat.LLC-stores >> >> > 2.428e+09 +11.3% 2.702e+09 TOTAL perf-stat.LLC-loads >> >> > 2.788e+11 +8.6% 3.029e+11 TOTAL perf-stat.dTLB-stores >> >> > 8.66e+08 +10.8% 9.594e+08 TOTAL perf-stat.LLC-prefetches >> >> > 1.117e+09 +10.5% 1.234e+09 TOTAL perf-stat.dTLB-store-misses >> >> > 1.705e+09 +5.3% 1.796e+09 TOTAL perf-stat.L1-dcache-store-misses >> >> > 5.671e+09 +6.1% 6.015e+09 TOTAL perf-stat.L1-dcache-load-misses >> >> > 8.794e+10 +3.6% 9.109e+10 TOTAL perf-stat.L1-dcache-stores >> >> > 3.46e+09 +4.6% 3.618e+09 TOTAL perf-stat.cache-references >> >> > 8.696e+08 +1.8% 8.849e+08 TOTAL perf-stat.cache-misses >> >> > 1613129 +2.6% 1655724 TOTAL perf-stat.context-switches >> >> > >> >> > All of the changes happen in one of our test box, which has a DX58SO >> >> > baseboard and 4-core CPU. The boot dmesg and kconfig are attached. >> >> > We can test more boxes if necessary. >> >> >> >> How do you run perf stat? >> > >> > perf stat -a $(-e hardware, cache, software events) >> > >> >> Curious that you notice this now, its a fairly old commit. >> > >> > Yeah, we are feeding old kernels to the 0day performance test system, too. :) >> > >> >> IIRC we did have a few wobbles with that, but I cannot remember much >> >> detail. >> >> >> >> The biggest difference between before and after that patch is that we'd >> >> rotate while the core is 'idle'. So if you do something like 'perf stat >> >> -a' and have significant idle time it does indeed make a difference. >> > >> > It is 'perf stat -a'; the CPU is mostly idle because it's an IO workload. >> > >> > btw, we find another commit that changed some perf-stat output: >> > >> > 2f7f73a520 ("perf/x86: Fix shared register mutual exclusion enforcement") >> > >> > Comparing to its parent commit: >> > >> > 069e0c3c4058147 2f7f73a52078b667d64df16ea >> > --------------- ------------------------- >> > 1.308e+08 ~26% -77.8% 29029594 ~12% fat/micro/dd-write/1HDD-deadline-xfs-10dd >> > 1.308e+08 -77.8% 29029594 TOTAL perf-stat.LLC-prefetch-misses >> > >> > 069e0c3c4058147 2f7f73a52078b667d64df16ea >> > --------------- ------------------------- >> > 97086131 ~ 7% -71.0% 28127157 ~11% fat/micro/dd-write/1HDD-deadline-xfs-10dd >> > 97086131 -71.0% 28127157 TOTAL perf-stat.node-prefetches >> > >> > 069e0c3c4058147 2f7f73a52078b667d64df16ea >> > --------------- ------------------------- >> > 1.4e+08 ~ 3% -56.6% 60744486 ~ 9% fat/micro/dd-write/1HDD-deadline-xfs-10dd >> > 1.4e+08 -56.6% 60744486 TOTAL perf-stat.LLC-load-misses >> > >> > 069e0c3c4058147 2f7f73a52078b667d64df16ea >> > --------------- ------------------------- >> > 6.967e+08 ~ 0% -49.6% 3.513e+08 ~ 6% fat/micro/dd-write/1HDD-deadline-xfs-10dd >> > 6.967e+08 -49.6% 3.513e+08 TOTAL perf-stat.node-stores >> > >> > 069e0c3c4058147 2f7f73a52078b667d64df16ea >> > --------------- ------------------------- >> > 1.933e+09 ~ 1% -43.0% 1.103e+09 ~ 2% fat/micro/dd-write/1HDD-deadline-xfs-10dd >> > 1.933e+09 -43.0% 1.103e+09 TOTAL perf-stat.LLC-stores >> > >> > 069e0c3c4058147 2f7f73a52078b667d64df16ea >> > --------------- ------------------------- >> > 7.013e+08 ~ 5% -55.5% 3.118e+08 ~ 4% fat/micro/dd-write/1HDD-deadline-btrfs-100dd >> > 6.775e+09 ~ 1% -20.4% 5.391e+09 ~ 1% lkp-ws02/micro/dd-write/11HDD-JBOD-cfq-ext4-1dd >> > 7.477e+09 -23.7% 5.703e+09 TOTAL perf-stat.LLC-store-misses >> > >> > 069e0c3c4058147 2f7f73a52078b667d64df16ea >> > --------------- ------------------------- >> > 2.294e+09 ~ 1% -10.0% 2.065e+09 ~ 0% lkp-ws02/micro/dd-write/11HDD-JBOD-cfq-ext4-1dd >> > 2.294e+09 -10.0% 2.065e+09 TOTAL perf-stat.LLC-prefetches >> > >> > 069e0c3c4058147 2f7f73a52078b667d64df16ea >> > --------------- ------------------------- >> > 8.685e+09 ~ 0% -10.0% 7.814e+09 ~ 1% lkp-ws02/micro/dd-write/11HDD-JBOD-cfq-ext4-1dd >> > 8.685e+09 -10.0% 7.814e+09 TOTAL perf-stat.cache-misses >> > >> > 069e0c3c4058147 2f7f73a52078b667d64df16ea >> > --------------- ------------------------- >> > 1.591e+12 ~ 0% -8.7% 1.453e+12 ~ 1% lkp-ws02/micro/dd-write/11HDD-JBOD-cfq-ext4-1dd >> > 1.591e+12 -8.7% 1.453e+12 TOTAL perf-stat.dTLB-loads >> > >> > >> > Thanks, >> > Fengguang -- 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/