Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755336AbbHFOUc (ORCPT ); Thu, 6 Aug 2015 10:20:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54704 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753915AbbHFOU2 (ORCPT ); Thu, 6 Aug 2015 10:20:28 -0400 Date: Thu, 6 Aug 2015 16:18:20 +0200 From: Oleg Nesterov To: Jason Low Cc: Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org, Frederic Weisbecker , "Paul E. McKenney" , Davidlohr Bueso , Mike Galbraith , terry.rudd@hp.com, Rik van Riel , Waiman Long , Scott J Norton Subject: Re: [RFC PATCH] timer: Improve itimers scalability Message-ID: <20150806141820.GA8258@redhat.com> References: <1438734584.2927.15.camel@j-VirtualBox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1438734584.2927.15.camel@j-VirtualBox> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1928 Lines: 58 On 08/04, Jason Low wrote: > > @@ -973,13 +981,6 @@ static void check_process_timers(struct task_struct *tsk, > virt_expires = check_timers_list(++timers, firing, utime); > sched_expires = check_timers_list(++timers, firing, sum_sched_runtime); > > - /* > - * Check for the special case process timers. > - */ > - check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime, > - SIGPROF); > - check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime, > - SIGVTALRM); > soft = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); > if (soft != RLIM_INFINITY) { > unsigned long psecs = cputime_to_secs(ptime); > @@ -1010,11 +1011,21 @@ static void check_process_timers(struct task_struct *tsk, > } > } > > + /* > + * Check for the special case process timers. > + */ > + check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime, > + SIGPROF); > + check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime, > + SIGVTALRM); > + Not sure I understand this part... looks wrong actually, please note that RLIMIT_CPU block above may need to update prof_expires _after_ check_cpu_itimer(), or I am totally confused. > if (READ_ONCE(sig->cputimer.running)) { > struct task_cputime group_sample; > > + /* > + * If another thread in the group is already checking > + * for the thread group cputimer, then we will skip that. > + */ > + if (READ_ONCE(sig->cputimer.is_checking_timer)) > + return 0; > + Cosmetic, I won't insist, but this is not symmetrical to ->running check, if (READ_ONCE(sig->cputimer.running) && !READ_ONCE(sig->cputimer.is_checking_timer)) looks a littke bit better to me. Oleg. -- 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/