From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sun, 1 May 2005 21:12:57 -0700 From: William Lee Irwin III Subject: Re: [PATCH]: VM 7/8 cluster pageout Message-ID: <20050502041257.GL2104@holomorphy.com> References: <16994.40699.267629.21475@gargle.gargle.HOWL> <20050425211514.29e7c86b.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050425211514.29e7c86b.akpm@osdl.org> Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: Nikita Danilov , linux-mm@kvack.org List-ID: Nikita Danilov wrote: >> Implement pageout clustering at the VM level. On Mon, Apr 25, 2005 at 09:15:14PM -0700, Andrew Morton wrote: > I had something like this happening in 2.5.10(ish), but ended up deciding > it was all too complex and writeout from the LRU is rare and the pages are > probably close-by on the LRU and the elevator sorting would catch most > cases so I tossed it all out. > Plus some of your other patches make LRU-based writeout even less common. Sorry for chiming in late on this issue. I would be careful in dismissing the case as "rare"; what I've discovered in this kind of performance scenario is that the rare case happens to someone, who is willing to tolerate poor performance and understands they're not the common case, but discovers pathological performance instead and cries out for help (unfortunately, this is all subjective). I'd be glad to see some bulletproofing of the VM against this case go into mainline, not to specifically recommend this approach against any other. By and large I've seen writeout from the LRU get dismissed and I'm convinced that although it should be rare, some (moderate?) steps are in order to ensure the degradation from such is not too severe (though poor performance is can be tolerated, pathological can't). -- wli -- 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: aart@kvack.org