From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934883AbXHNWKZ (ORCPT ); Tue, 14 Aug 2007 18:10:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755993AbXHNVog (ORCPT ); Tue, 14 Aug 2007 17:44:36 -0400 Received: from one.firstfloor.org ([213.235.205.2]:32836 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934576AbXHNVoe (ORCPT ); Tue, 14 Aug 2007 17:44:34 -0400 Date: Tue, 14 Aug 2007 23:44:30 +0200 From: Andi Kleen To: Christoph Lameter Cc: Andi Kleen , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC 4/9] Atomic reclaim: Save irq flags in vmscan.c Message-ID: <20070814214430.GD23308@one.firstfloor.org> References: <20070814203329.GA22202@one.firstfloor.org> <20070814204454.GC22202@one.firstfloor.org> <20070814212355.GA23308@one.firstfloor.org> <20070814212955.GC23308@one.firstfloor.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 14, 2007 at 02:37:27PM -0700, Christoph Lameter wrote: > On Tue, 14 Aug 2007, Andi Kleen wrote: > > > > We already have such a flag in the zone structure > > > > Zone structure is not strictly CPU local so it's broader > > than needed. But it might work. > > We could convert this into a per cpu array? Perhaps. That would make it more expensive to read for its current users though. > But that still creates lots of overhead each time we take the lru lock! A lot of overhead in what way? Setting a flag in a cache hot per CPU data variable shouldn't be more than a few cycles. -Andi