From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935721AbXHNWXM (ORCPT ); Tue, 14 Aug 2007 18:23:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1765837AbXHNWUb (ORCPT ); Tue, 14 Aug 2007 18:20:31 -0400 Received: from netops-testserver-3-out.sgi.com ([192.48.171.28]:51224 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S934766AbXHNWU2 (ORCPT ); Tue, 14 Aug 2007 18:20:28 -0400 Date: Tue, 14 Aug 2007 15:20:28 -0700 (PDT) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Andi Kleen cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC 4/9] Atomic reclaim: Save irq flags in vmscan.c In-Reply-To: <20070814221616.GG23308@one.firstfloor.org> Message-ID: References: <20070814204454.GC22202@one.firstfloor.org> <20070814212355.GA23308@one.firstfloor.org> <20070814212955.GC23308@one.firstfloor.org> <20070814214430.GD23308@one.firstfloor.org> <20070814215659.GF23308@one.firstfloor.org> <20070814221616.GG23308@one.firstfloor.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 15 Aug 2007, Andi Kleen wrote: > > > The interrupt handler shouldn't touch zone_flag. If it wants > > > to it would need to be converted to a local_t and incremented/decremented > > > (should be about the same cost at least on architectures with sane > > > local_t implementation) > > > > That would mean we need to fork the code for reclaim? > > Not with the local_t increment. Ok I have a vague idea on how this could but its likely that the changes make things worse rather than better. Additional reference to a new cacheline (per cpu but still), preempt disable. Lots of code at all call sites. Interrupt enable/disable is quite efficient in recent processors.