Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761229Ab3D3ReI (ORCPT ); Tue, 30 Apr 2013 13:34:08 -0400 Received: from a10-63.smtp-out.amazonses.com ([54.240.10.63]:50631 "EHLO a10-63.smtp-out.amazonses.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760805Ab3D3ReG (ORCPT ); Tue, 30 Apr 2013 13:34:06 -0400 X-Greylist: delayed 330 seconds by postgrey-1.27 at vger.kernel.org; Tue, 30 Apr 2013 13:34:06 EDT Date: Tue, 30 Apr 2013 17:28:34 +0000 From: Christoph Lameter X-X-Sender: cl@gentwo.org To: Tim Chen cc: Andrew Morton , Tejun Heo , Al Viro , Dave Hansen , Andi Kleen , linux-kernel , linux-mm Subject: Re: [PATCH 1/2] Make the batch size of the percpu_counter configurable In-Reply-To: <1367339009.27102.174.camel@schen9-DESK> Message-ID: <0000013e5bfd1548-a6ef7962-7b00-495b-8e83-d7a08413e165-000000@email.amazonses.com> References: <0000013e5b24d2c5-9b899862-e2fd-4413-8094-4f1e5a0c0f62-000000@email.amazonses.com> <1367339009.27102.174.camel@schen9-DESK> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-SES-Outgoing: 2013.04.30-54.240.10.63 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1111 Lines: 30 On Tue, 30 Apr 2013, Tim Chen wrote: > On Tue, 2013-04-30 at 13:32 +0000, Christoph Lameter wrote: > > On Mon, 29 Apr 2013, Tim Chen wrote: > > > > > diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h > > > index d5dd465..5ca7df5 100644 > > > --- a/include/linux/percpu_counter.h > > > +++ b/include/linux/percpu_counter.h > > > @@ -22,6 +22,7 @@ struct percpu_counter { > > > struct list_head list; /* All percpu_counters are on a list */ > > > #endif > > > s32 __percpu *counters; > > > + int *batch ____cacheline_aligned_in_smp; > > > }; > > > > What is this for and why does it have that alignmend? > > I was assuming that if batch is frequently referenced, it probably > should not share a cache line with the counters field. And why is it a pointer? And the pointer is so frequently changed that it needs it own cache line? -- 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/