From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yb0-f200.google.com (mail-yb0-f200.google.com [209.85.213.200]) by kanga.kvack.org (Postfix) with ESMTP id F0D4F6B0038 for ; Wed, 14 Dec 2016 06:06:13 -0500 (EST) Received: by mail-yb0-f200.google.com with SMTP id 186so30325524yby.5 for ; Wed, 14 Dec 2016 03:06:13 -0800 (PST) Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com. [148.163.158.5]) by mx.google.com with ESMTPS id x14si15800311ywg.381.2016.12.14.03.06.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 14 Dec 2016 03:06:13 -0800 (PST) Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id uBEB3sLY106244 for ; Wed, 14 Dec 2016 06:06:13 -0500 Received: from e32.co.us.ibm.com (e32.co.us.ibm.com [32.97.110.150]) by mx0b-001b2d01.pphosted.com with ESMTP id 27ayxs0n8n-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Wed, 14 Dec 2016 06:06:12 -0500 Received: from localhost by e32.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 14 Dec 2016 04:06:11 -0700 Date: Wed, 14 Dec 2016 03:06:09 -0800 From: "Paul E. McKenney" Subject: Re: Fw: [lkp-developer] [sched,rcu] cf7a2dca60: [No primary change] +186% will-it-scale.time.involuntary_context_switches Reply-To: paulmck@linux.vnet.ibm.com References: <20161213151408.GC3924@linux.vnet.ibm.com> <20161214095425.GE25573@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20161214095425.GE25573@dhcp22.suse.cz> Message-Id: <20161214110609.GK3924@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, peterz@infradead.org On Wed, Dec 14, 2016 at 10:54:25AM +0100, Michal Hocko wrote: > 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. My first thought is to wait for the grace period to age further before checking, the idea being to avoid increasing cond_resched() overhead any further. But if that doesn't work, then yes, I may have to look at adding more checks to cond_resched(). > 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! Here is hoping for an eventual solution. ;-) 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. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org