From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f197.google.com (mail-qt0-f197.google.com [209.85.216.197]) by kanga.kvack.org (Postfix) with ESMTP id C1E366B0038 for ; Wed, 14 Dec 2016 04:54:27 -0500 (EST) Received: by mail-qt0-f197.google.com with SMTP id l20so9102960qta.3 for ; Wed, 14 Dec 2016 01:54:27 -0800 (PST) Received: from mail-qk0-f194.google.com (mail-qk0-f194.google.com. [209.85.220.194]) by mx.google.com with ESMTPS id i138si18422623qke.214.2016.12.14.01.54.27 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 14 Dec 2016 01:54:27 -0800 (PST) Received: by mail-qk0-f194.google.com with SMTP id x190so1723438qkb.0 for ; Wed, 14 Dec 2016 01:54:27 -0800 (PST) Date: Wed, 14 Dec 2016 10:54:25 +0100 From: Michal Hocko Subject: Re: Fw: [lkp-developer] [sched,rcu] cf7a2dca60: [No primary change] +186% will-it-scale.time.involuntary_context_switches Message-ID: <20161214095425.GE25573@dhcp22.suse.cz> References: <20161213151408.GC3924@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20161213151408.GC3924@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Paul E. McKenney" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, peterz@infradead.org On Tue 13-12-16 07:14:08, Paul E. McKenney wrote: > Just FYI for the moment... > > So even with the slowed-down checking, making cond_resched() do what > cond_resched_rcu_qs() does results in a smallish but quite measurable > degradation according to 0day. So if I understand those results properly, the reason seems to be the increased involuntary context switches, right? Or am I misreading the data? I am looking at your "sched,rcu: Make cond_resched() provide RCU quiescent state" in linux-next and I am wondering whether rcu_all_qs has to be called unconditionally and not only when should_resched failed few times? I guess you have discussed that with Peter already but do not remember the outcome. Thanks for letting my know! > I will try some things to reduce the > impact, but it is quite possible that we will need to live with both > interfaces. Thanks a lot for your time! > Thanx, Paul > > ----- Forwarded message from kernel test robot ----- > > Date: Mon, 12 Dec 2016 13:52:28 +0800 > From: kernel test robot > TO: "Paul E. McKenney" > Cc: lkp@01.org > Subject: [lkp-developer] [sched,rcu] cf7a2dca60: [No primary change] +186% > will-it-scale.time.involuntary_context_switches > > Greeting, > > There is no primary kpi change in this test, below is the data collected through multiple monitors running background just for your information. > > > commit: cf7a2dca6056544bb04a8f819fbbdb415bdb2933 ("sched,rcu: Make cond_resched() provide RCU quiescent state") > https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2016.12.05c > > in testcase: will-it-scale > on test machine: 32 threads Intel(R) Xeon(R) CPU E5-2680 0 @ 2.70GHz with 64G memory > with following parameters: > > test: unlink2 > cpufreq_governor: performance > > test-description: Will It Scale takes a testcase and runs it from 1 through to n parallel copies to see if the testcase will scale. It builds both a process and threads based test in order to see any differences between the two. > test-url: https://github.com/antonblanchard/will-it-scale > > > > Details are as below: > --------------------------------------------------------------------------------------------------> > > > To reproduce: > > git clone git://git.kernel.org/pub/scm/linux/kernel/git/wfg/lkp-tests.git > cd lkp-tests > bin/lkp install job.yaml # job file is attached in this email > bin/lkp run job.yaml > > testcase/path_params/tbox_group/run: will-it-scale/unlink2-performance/lkp-sb03 > > 15705d6709cb6ba6 cf7a2dca6056544bb04a8f819f > ---------------- -------------------------- > %stddev change %stddev > \ | \ > 116286 114432 will-it-scale.per_process_ops > 20902 +- 5% 186% 59731 +- 5% will-it-scale.time.involuntary_context_switches > 2694 +- 8% 61% 4344 vmstat.system.cs > 10903 +- 99% -1e+04 148 +- 5% latency_stats.max.wait_on_page_bit.__migration_entry_wait.migration_entry_wait.do_swap_page.handle_mm_fault.__do_page_fault.do_page_fault.page_fault > 3583 +- 38% 1e+04 14010 +- 51% latency_stats.sum.ep_poll.SyS_epoll_wait.entry_SYSCALL_64_fastpath > 4143 +- 24% 1e+04 14549 +- 51% latency_stats.sum.ep_poll.SyS_epoll_wait.do_syscall_64.return_from_SYSCALL_64 > 271108 +- 71% -2e+05 66364 +- 32% latency_stats.sum.wait_on_page_bit.__migration_entry_wait.migration_entry_wait.do_swap_page.handle_mm_fault.__do_page_fault.do_page_fault.page_fault > 834637 +- 8% 62% 1351381 perf-stat.context-switches > 16449 +- 3% 54% 25349 +- 3% perf-stat.cpu-migrations > 25.94 35% 35.02 perf-stat.node-store-miss-rate% > 2.534e+09 32% 3.335e+09 perf-stat.node-store-misses > 1.002e+12 4% 1.043e+12 perf-stat.dTLB-stores > 50923913 3% 52692115 perf-stat.iTLB-loads > 1.696e+12 1.745e+12 perf-stat.dTLB-loads > 1.258e+12 1.291e+12 perf-stat.branch-instructions > 6.132e+12 6.274e+12 perf-stat.instructions > 0.37 0.38 perf-stat.ipc > 0.37 -3% 0.35 perf-stat.branch-miss-rate% > 29.83 -4% 28.66 perf-stat.cache-miss-rate% > 1.117e+10 -4% 1.071e+10 perf-stat.cache-misses > 7.232e+09 -14% 6.187e+09 perf-stat.node-stores -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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