From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [PATCH 5/6] vmscan: Write out ranges of pages contiguous to the inode where possible Date: Fri, 11 Jun 2010 14:33:37 -0700 Message-ID: <20100611143337.53a06329.akpm@linux-foundation.org> References: <1275987745-21708-1-git-send-email-mel@csn.ul.ie> <1275987745-21708-6-git-send-email-mel@csn.ul.ie> <20100610231045.7fcd6f9d.akpm@linux-foundation.org> <20100611124936.GB8798@csn.ul.ie> <20100611120730.26a29366.akpm@linux-foundation.org> <20100611204411.GD9946@csn.ul.ie> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Dave Chinner , Chris Mason , Nick Piggin , Rik van Riel To: Mel Gorman Return-path: In-Reply-To: <20100611204411.GD9946@csn.ul.ie> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Fri, 11 Jun 2010 21:44:11 +0100 Mel Gorman wrote: > > Well. The main problem is that we're doing too much IO off the LRU of > > course. > > > > What would be considered "too much IO"? Enough to slow things down ;) This problem used to hurt a lot. Since those times we've decreased the default value of /proc/sys/vm/dirty*ratio by a lot, which surely papered over this problem a lot. We shouldn't forget that those ratios _are_ tunable, after all. If we make a change which explodes the kernel when someone's tuned to 40% then that's a problem and we'll need to scratch our heads over the magnitude of that problem. As for a workload which triggers the problem on a large machine which is tuned to 20%/10%: dunno. If we're reliably activating pages when dirtying them then perhaps it's no longer a problem with the default tuning. I'd do some testing with mem=256M though - that has a habit of triggering weirdnesses. btw, I'm trying to work out if zap_pte_range() really needs to run set_page_dirty(). Didn't (pte_dirty() && !PageDirty()) pages get themselves stamped out? -- 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