Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761297Ab3D3SKJ (ORCPT ); Tue, 30 Apr 2013 14:10:09 -0400 Received: from mail-pd0-f181.google.com ([209.85.192.181]:50696 "EHLO mail-pd0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752551Ab3D3SKG (ORCPT ); Tue, 30 Apr 2013 14:10:06 -0400 Message-ID: <1367345403.11020.1.camel@edumazet-glaptop> Subject: Re: [PATCH 1/2] Make the batch size of the percpu_counter configurable From: Eric Dumazet To: Tim Chen Cc: Christoph Lameter , Andrew Morton , Tejun Heo , Al Viro , Dave Hansen , Andi Kleen , linux-kernel , linux-mm Date: Tue, 30 Apr 2013 11:10:03 -0700 In-Reply-To: <1367339009.27102.174.camel@schen9-DESK> References: <0000013e5b24d2c5-9b899862-e2fd-4413-8094-4f1e5a0c0f62-000000@email.amazonses.com> <1367339009.27102.174.camel@schen9-DESK> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1267 Lines: 35 On Tue, 2013-04-30 at 09:23 -0700, 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. But 'counters' field has the same requirement. Its supposed to be read only field. So please remove this '____cacheline_aligned_in_smp', as it makes the whole struct percpu_counter at least two cache lines wide, for no obvious reason. -- 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/