From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754399AbbJNTHp (ORCPT ); Wed, 14 Oct 2015 15:07:45 -0400 Received: from g1t6225.austin.hp.com ([15.73.96.126]:46526 "EHLO g1t6225.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754002AbbJNTHn (ORCPT ); Wed, 14 Oct 2015 15:07:43 -0400 From: Jason Low To: Peter Zijlstra , Ingo Molnar , Thomas Gleixner Cc: linux-kernel@vger.kernel.org, Oleg Nesterov , "Paul E. McKenney" , Frederic Weisbecker , Davidlohr Bueso , Steven Rostedt , Andrew Morton , George Spelvin , hideaki.kimura@hpe.com, terry.rudd@hpe.com, scott.norton@hpe.com, Jason Low Subject: [PATCH v2 0/4] timer: Improve itimers scalability Date: Wed, 14 Oct 2015 12:07:52 -0700 Message-Id: <1444849677-29330-1-git-send-email-jason.low2@hp.com> X-Mailer: git-send-email 1.7.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org While running a database workload on a 16 socket machine, there were scalability issues related to itimers. The following link contains a more detailed summary of the issues at the application level. https://lkml.org/lkml/2015/8/26/737 Commit 1018016c706f addressed the issue with the thread_group_cputimer spinlock taking up a significant portion of total run time. This patch series addresses the secondary issue where a lot of time is spent trying to acquire the sighand lock. It was found in some cases that 200+ threads were simultaneously contending for the same sighand lock, reducing throughput by more than 30%. With this patch set (along with commit 1018016c706f mentioned above), the performance hit of itimers almost completely goes away on the 16 socket system. Jason Low (4): timer: Optimize fastpath_timer_check() timer: Check thread timers only when there are active thread timers timer: Convert cputimer->running to bool timer: Reduce unnecessary sighand lock contention include/linux/init_task.h | 3 +- include/linux/sched.h | 9 ++++-- kernel/fork.c | 2 +- kernel/time/posix-cpu-timers.c | 63 ++++++++++++++++++++++++++++----------- 4 files changed, 54 insertions(+), 23 deletions(-) -- 1.7.2.5