From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [RFC 4/9] Atomic reclaim: Save irq flags in vmscan.c References: <20070814153021.446917377@sgi.com> <20070814153501.766137366@sgi.com> From: Andi Kleen Date: 14 Aug 2007 22:02:23 +0200 In-Reply-To: <20070814153501.766137366@sgi.com> Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: Christoph Lameter writes: > Reclaim can be called with interrupts disabled in atomic reclaim. > vmscan.c is currently using spinlock_irq(). Switch to spin_lock_irqsave(). I like the idea in principle. If this fully works out we could potentially keep less memory free by default which would be a good thing in general: free memory is bad memory. But would be interesting to measure what the lock changes do to interrupt latency. Probably nothing good. A more benign alternative might be to just set a per CPU flag during these critical sections and then only do atomic reclaim on a local interrupt when the flag is not set. That would make it a little less reliable, but much less intrusive and with some luck still give many of the benefits. -Andi -- 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