Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965485AbeAJM00 (ORCPT + 1 other); Wed, 10 Jan 2018 07:26:26 -0500 Received: from terminus.zytor.com ([65.50.211.136]:40973 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932538AbeAJM0T (ORCPT ); Wed, 10 Jan 2018 07:26:19 -0500 Date: Wed, 10 Jan 2018 04:14:43 -0800 From: tip-bot for Joel Fernandes Message-ID: Cc: matt@codeblueprint.co.uk, peterz@infradead.org, atish.patra@oracle.com, rjw@rjwysocki.net, rohit.k.jain@oracle.com, brendan.jackman@arm.com, smuckle@google.com, linux-kernel@vger.kernel.org, srinivas.pandruvada@linux.intel.com, morten.rasmussen@arm.com, mingo@kernel.org, torvalds@linux-foundation.org, rostedt@goodmis.org, markivx@codeaurora.org, Chris.Redpath@arm.com, hpa@zytor.com, joelaf@google.com, skannan@quicinc.com, lenb@kernel.org, dietmar.eggemann@arm.com, vincent.guittot@linaro.org, fweisbec@gmail.com, tglx@linutronix.de, juri.lelli@arm.com, viresh.kumar@linaro.org, patrick.bellasi@arm.com Reply-To: rjw@rjwysocki.net, brendan.jackman@arm.com, rohit.k.jain@oracle.com, atish.patra@oracle.com, peterz@infradead.org, matt@codeblueprint.co.uk, linux-kernel@vger.kernel.org, smuckle@google.com, torvalds@linux-foundation.org, srinivas.pandruvada@linux.intel.com, morten.rasmussen@arm.com, mingo@kernel.org, rostedt@goodmis.org, markivx@codeaurora.org, skannan@quicinc.com, joelaf@google.com, lenb@kernel.org, Chris.Redpath@arm.com, hpa@zytor.com, fweisbec@gmail.com, tglx@linutronix.de, dietmar.eggemann@arm.com, vincent.guittot@linaro.org, patrick.bellasi@arm.com, juri.lelli@arm.com, viresh.kumar@linaro.org In-Reply-To: <20171214212158.188190-1-joelaf@google.com> References: <20171214212158.188190-1-joelaf@google.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/fair: Consider RT/IRQ pressure in capacity_spare_wake() Git-Commit-ID: f453ae2200b0d1b7abc0c3794ce088899ac7a2af X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: Commit-ID: f453ae2200b0d1b7abc0c3794ce088899ac7a2af Gitweb: https://git.kernel.org/tip/f453ae2200b0d1b7abc0c3794ce088899ac7a2af Author: Joel Fernandes AuthorDate: Thu, 14 Dec 2017 13:21:58 -0800 Committer: Ingo Molnar CommitDate: Wed, 10 Jan 2018 11:30:28 +0100 sched/fair: Consider RT/IRQ pressure in capacity_spare_wake() capacity_spare_wake() in the slow path influences choice of idlest groups, as we search for groups with maximum spare capacity. In scenarios where RT pressure is high, a sub optimal group can be chosen and hurt performance of the task being woken up. Fix this by using capacity_of() instead of capacity_orig_of() in capacity_spare_wake(). Tests results from improvements with this change are below. More tests were also done by myself and Matt Fleming to ensure no degradation in different benchmarks. 1) Rohit ran barrier.c test (details below) with following improvements: ------------------------------------------------------------------------ This was Rohit's original use case for a patch he posted at [1] however from his recent tests he showed my patch can replace his slow path changes [1] and there's no need to selectively scan/skip CPUs in find_idlest_group_cpu in the slow path to get the improvement he sees. barrier.c (open_mp code) as a micro-benchmark. It does a number of iterations and barrier sync at the end of each for loop. Here barrier,c is running in along with ping on CPU 0 and 1 as: 'ping -l 10000 -q -s 10 -f hostX' barrier.c can be found at: http://www.spinics.net/lists/kernel/msg2506955.html Following are the results for the iterations per second with this micro-benchmark (higher is better), on a 44 core, 2 socket 88 Threads Intel x86 machine: +--------+------------------+---------------------------+ |Threads | Without patch | With patch | | | | | +--------+--------+---------+-----------------+---------+ | | Mean | Std Dev | Mean | Std Dev | +--------+--------+---------+-----------------+---------+ |1 | 539.36 | 60.16 | 572.54 (+6.15%) | 40.95 | |2 | 481.01 | 19.32 | 530.64 (+10.32%)| 56.16 | |4 | 474.78 | 22.28 | 479.46 (+0.99%) | 18.89 | |8 | 450.06 | 24.91 | 447.82 (-0.50%) | 12.36 | |16 | 436.99 | 22.57 | 441.88 (+1.12%) | 7.39 | |32 | 388.28 | 55.59 | 429.4 (+10.59%)| 31.14 | |64 | 314.62 | 6.33 | 311.81 (-0.89%) | 11.99 | +--------+--------+---------+-----------------+---------+ 2) ping+hackbench test on bare-metal sever (by Rohit) ----------------------------------------------------- Here hackbench is running in threaded mode along with, running ping on CPU 0 and 1 as: 'ping -l 10000 -q -s 10 -f hostX' This test is running on 2 socket, 20 core and 40 threads Intel x86 machine: Number of loops is 10000 and runtime is in seconds (Lower is better). +--------------+-----------------+--------------------------+ |Task Groups | Without patch | With patch | | +-------+---------+----------------+---------+ |(Groups of 40)| Mean | Std Dev | Mean | Std Dev | +--------------+-------+---------+----------------+---------+ |1 | 0.851 | 0.007 | 0.828 (+2.77%)| 0.032 | |2 | 1.083 | 0.203 | 1.087 (-0.37%)| 0.246 | |4 | 1.601 | 0.051 | 1.611 (-0.62%)| 0.055 | |8 | 2.837 | 0.060 | 2.827 (+0.35%)| 0.031 | |16 | 5.139 | 0.133 | 5.107 (+0.63%)| 0.085 | |25 | 7.569 | 0.142 | 7.503 (+0.88%)| 0.143 | +--------------+-------+---------+----------------+---------+ [1] https://patchwork.kernel.org/patch/9991635/ Matt Fleming also ran several different hackbench tests and cyclic test to santiy-check that the patch doesn't harm other usecases. Tested-by: Matt Fleming Tested-by: Rohit Jain Signed-off-by: Joel Fernandes Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Vincent Guittot Reviewed-by: Dietmar Eggemann Cc: Atish Patra Cc: Brendan Jackman Cc: Chris Redpath Cc: Frederic Weisbecker Cc: Juri Lelli Cc: Len Brown Cc: Linus Torvalds Cc: Morten Ramussen Cc: Patrick Bellasi Cc: Peter Zijlstra Cc: Rafael J. Wysocki Cc: Saravana Kannan Cc: Srinivas Pandruvada Cc: Steve Muckle Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Vikram Mulukutla Cc: Viresh Kumar Link: http://lkml.kernel.org/r/20171214212158.188190-1-joelaf@google.com Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index de43bd8..6e775ac 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5770,7 +5770,7 @@ static unsigned long cpu_util_wake(int cpu, struct task_struct *p); static unsigned long capacity_spare_wake(int cpu, struct task_struct *p) { - return capacity_orig_of(cpu) - cpu_util_wake(cpu, p); + return max_t(long, capacity_of(cpu) - cpu_util_wake(cpu, p), 0); } /*