Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752669AbbLCSXG (ORCPT ); Thu, 3 Dec 2015 13:23:06 -0500 Received: from mail-pf0-f175.google.com ([209.85.192.175]:34430 "EHLO mail-pf0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752571AbbLCSXF (ORCPT ); Thu, 3 Dec 2015 13:23:05 -0500 From: bsegall@google.com To: Peter Zijlstra Cc: Waiman Long , Ingo Molnar , linux-kernel@vger.kernel.org, Yuyang Du , Paul Turner , Morten Rasmussen , Scott J Norton , Douglas Hatch Subject: Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own cacheline References: <1449081710-20185-1-git-send-email-Waiman.Long@hpe.com> <1449081710-20185-3-git-send-email-Waiman.Long@hpe.com> <20151203111209.GX3816@twins.programming.kicks-ass.net> <20151203181714.GT17308@twins.programming.kicks-ass.net> Date: Thu, 03 Dec 2015 10:23:01 -0800 In-Reply-To: <20151203181714.GT17308@twins.programming.kicks-ass.net> (Peter Zijlstra's message of "Thu, 3 Dec 2015 19:17:14 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2009 Lines: 57 Peter Zijlstra writes: > On Thu, Dec 03, 2015 at 09:56:02AM -0800, bsegall@google.com wrote: >> Peter Zijlstra writes: > >> > @@ -7402,11 +7405,12 @@ void __init sched_init(void) >> > #endif /* CONFIG_RT_GROUP_SCHED */ >> > >> > #ifdef CONFIG_CGROUP_SCHED >> > + task_group_cache = KMEM_CACHE(task_group, 0); >> > + >> > list_add(&root_task_group.list, &task_groups); >> > INIT_LIST_HEAD(&root_task_group.children); >> > INIT_LIST_HEAD(&root_task_group.siblings); >> > autogroup_init(&init_task); >> > - >> > #endif /* CONFIG_CGROUP_SCHED */ >> > >> > for_each_possible_cpu(i) { >> > --- a/kernel/sched/sched.h >> > +++ b/kernel/sched/sched.h >> > @@ -248,7 +248,12 @@ struct task_group { >> > unsigned long shares; >> > >> > #ifdef CONFIG_SMP >> > - atomic_long_t load_avg; >> > + /* >> > + * load_avg can be heavily contended at clock tick time, so put >> > + * it in its own cacheline separated from the fields above which >> > + * will also be accessed at each tick. >> > + */ >> > + atomic_long_t load_avg ____cacheline_aligned; >> > #endif >> > #endif >> > >> >> This loses the cacheline-alignment for task_group, is that ok? > > I'm a bit dense (its late) can you spell that out? Did you mean me > killing SLAB_HWCACHE_ALIGN? That should not matter because: > > #define KMEM_CACHE(__struct, __flags) kmem_cache_create(#__struct,\ > sizeof(struct __struct), __alignof__(struct __struct),\ > (__flags), NULL) > > picks up the alignment explicitly. > > And struct task_group having one cacheline aligned member, means that > the alignment of the composite object (the struct proper) must be an > integer multiple of this (typically 1). Ah, yeah, I forgot about this, my fault. -- 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/