From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta8.messagelabs.com (mail6.bemta8.messagelabs.com [216.82.243.55]) by kanga.kvack.org (Postfix) with ESMTP id 670F36B016F for ; Thu, 13 Oct 2011 16:50:36 -0400 (EDT) Received: by vcbfk1 with SMTP id fk1so655739vcb.14 for ; Thu, 13 Oct 2011 13:50:35 -0700 (PDT) Date: Thu, 13 Oct 2011 13:50:32 -0700 From: Andrew Morton Subject: Re: [PATCH] Reduce vm_stat cacheline contention in __vm_enough_memory Message-Id: <20111013135032.7c2c54cd.akpm@linux-foundation.org> In-Reply-To: References: <20111012160202.GA18666@sgi.com> <20111012120118.e948f40a.akpm@linux-foundation.org> <20111013152355.GB6966@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Dimitri Sivanich , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Mel Gorman On Thu, 13 Oct 2011 10:54:30 -0500 (CDT) Christoph Lameter wrote: > On Thu, 13 Oct 2011, Dimitri Sivanich wrote: > > > > increase the allowed delta per zone if frequent updates occur via the > > > overflow checks in vmstat.c. See calculate_*_threshold there. > > > > I tried changing the threshold in both directions, with slower throughput in > > both cases. > > If that is the case check for the vm_stat cacheline being shared with > another hot kernel variable variable. Maybe that causes cacheline > eviction. yup. `nm -n vmlinux'. > If there are no updates occurring for a while (due to increased deltas > and/or vmstat updates) then the vm_stat cacheline should be able to stay > in shared mode in multiple processors and the performance should increase. > We could cacheline align vm_stat[]. But the thing is pretty small - we couild put each entry in its own cacheline. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org