From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx103.postini.com [74.125.245.103]) by kanga.kvack.org (Postfix) with SMTP id 9FE476B005D for ; Mon, 3 Dec 2012 14:57:21 -0500 (EST) Message-ID: <50BD03B7.2070401@redhat.com> Date: Mon, 03 Dec 2012 14:55:35 -0500 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 29/52] sched: Implement NUMA scanning backoff References: <1354473824-19229-1-git-send-email-mingo@kernel.org> <1354473824-19229-30-git-send-email-mingo@kernel.org> In-Reply-To: <1354473824-19229-30-git-send-email-mingo@kernel.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Peter Zijlstra , Paul Turner , Lee Schermerhorn , Christoph Lameter , Mel Gorman , Andrew Morton , Andrea Arcangeli , Linus Torvalds , Thomas Gleixner , Johannes Weiner , Hugh Dickins On 12/02/2012 01:43 PM, Ingo Molnar wrote: > Back off slowly from scanning, up to sysctl_sched_numa_scan_period_max > (1.6 seconds). Scan faster again if we were forced to switch to > another node. > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 8f0e6ba..59fea2e 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -865,8 +865,10 @@ static void task_numa_placement(struct task_struct *p) > } > } > > - if (max_node != p->numa_max_node) > + if (max_node != p->numa_max_node) { > sched_setnuma(p, max_node, task_numa_shared(p)); > + goto out_backoff; > + } > > p->numa_migrate_seq++; > if (sched_feat(NUMA_SETTLE) && Is that correct? It looks like the code only jumps to the out_backoff label after resetting p->numa_scan_period to sysctl_sched_numa_scan_period_min in sched_setnuma? Should it not be the other way around, slowly increasing the process's numa_scan_period when we do NOT do a sched_setnuma call for the process at all? > @@ -882,7 +884,11 @@ static void task_numa_placement(struct task_struct *p) > if (shared != task_numa_shared(p)) { > sched_setnuma(p, p->numa_max_node, shared); > p->numa_migrate_seq = 0; > + goto out_backoff; > } > + return; We can never reach the backoff code, except by an explicit goto, which is only there after a call to sched_setnuma. That is the opposite from what the changelog suggests... > +out_backoff: > + p->numa_scan_period = min(p->numa_scan_period * 2, sysctl_sched_numa_scan_period_max); > } > > /* > -- 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