From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 14 Aug 2007 15:41:53 -0700 (PDT) From: Christoph Lameter Subject: Re: [RFC 4/9] Atomic reclaim: Save irq flags in vmscan.c In-Reply-To: <20070814222150.GI23308@one.firstfloor.org> Message-ID: References: <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> <20070814222150.GI23308@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 Wed, 15 Aug 2007, Andi Kleen wrote: > > 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. > > The goal of this was not to be faster than interrupt disable, > but to avoid the interrupt latency impact. This might be a problem > when spending a lot of time inside the locks. Both. They need to be fast too and not complicate the kernel too much. I have not seen a serious holdoff case. The biggest issue is still the zone->lru lock but interrupts are always disabled for that one already. -- 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