From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx176.postini.com [74.125.245.176]) by kanga.kvack.org (Postfix) with SMTP id A7A1D6B0034 for ; Wed, 31 Jul 2013 11:38:27 -0400 (EDT) Date: Wed, 31 Jul 2013 17:38:21 +0200 From: Peter Zijlstra Subject: Re: [PATCH] sched, numa: Use {cpu, pid} to create task groups for shared faults Message-ID: <20130731153821.GE3008@twins.programming.kicks-ass.net> References: <1373901620-2021-1-git-send-email-mgorman@suse.de> <20130730113857.GR3008@twins.programming.kicks-ass.net> <20130731150751.GA15144@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130731150751.GA15144@twins.programming.kicks-ass.net> Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Srikar Dronamraju , Ingo Molnar , Andrea Arcangeli , Johannes Weiner , Linux-MM , LKML , riel@redhat.com On Wed, Jul 31, 2013 at 05:07:51PM +0200, Peter Zijlstra wrote: > @@ -1260,6 +1400,23 @@ void task_numa_fault(int last_cpupid, in > } > > /* > + * First accesses are treated as private, otherwise consider accesses > + * to be private if the accessing pid has not changed > + */ > + if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) { > + priv = 1; > + } else { > + int cpu, pid; > + > + cpu = cpupid_to_cpu(last_cpupid); > + pid = cpupid_to_pid(last_cpupid); > + > + priv = (pid == (p->pid & LAST__PID_MASK)); So Rik just pointed out that this condition is likely to generate false positives due to the birthday paradox. The problem with including cpu/nid information is another kind of false positives. We've no idea which is worse.. > + if (!priv) > + task_numa_group(p, cpu, pid); > + } -- 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