From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 14 Aug 2007 14:48:31 -0700 (PDT) From: Christoph Lameter Subject: Re: [RFC 4/9] Atomic reclaim: Save irq flags in vmscan.c In-Reply-To: <20070814214430.GD23308@one.firstfloor.org> Message-ID: References: <20070814203329.GA22202@one.firstfloor.org> <20070814204454.GC22202@one.firstfloor.org> <20070814212355.GA23308@one.firstfloor.org> <20070814212955.GC23308@one.firstfloor.org> <20070814214430.GD23308@one.firstfloor.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andi Kleen Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Tue, 14 Aug 2007, Andi Kleen wrote: > > 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. Could you be a bit more specific? Where do you want to place the data? What we are talking about is atomic_inc(&zone->reclaim_cpu[smp_processor_id()]); smp_wmb(); spin_lock(&zone->lru_lock); .... spin_unlock(&zone_lru_lock); smp_wmb(); atomic_dec(&zone->reclaim_cpu[smp_processor_id()]); That is not light weight. -- 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/ . Don't email: email@kvack.org