From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nikita Danilov MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <17006.2975.791376.558683@gargle.gargle.HOWL> Date: Tue, 26 Apr 2005 13:36:31 +0400 Subject: Re: [PATCH]: VM 6/8 page_referenced(): move dirty In-Reply-To: <20050426015518.2df35139.akpm@osdl.org> References: <16994.40677.105697.817303@gargle.gargle.HOWL> <20050425210016.6f8a47d1.akpm@osdl.org> <17006.127.376459.93584@gargle.gargle.HOWL> <20050426015518.2df35139.akpm@osdl.org> Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: linux-mm@kvack.org List-ID: Andrew Morton writes: > Nikita Danilov wrote: > > > > > > > > I can envision workloads (such as mmap 80% of memory and continuously dirty > > > it) which would end up performing continuous I/O with this patch. > > > > Below is a version that tries to move dirtiness to the struct page only > > if we are really going to deactivate the page. In your scenario above, > > continuously dirty pages will be on the active list, so it should be > > okay. > > OK, well it'll now increase the amount of I/O by a smaller amount. Trade > that off against possibly improved I/O patterns. But how do we know that > all this is a net gain? By looking at the (micro-) benchmarking results: 2.6.12-rc2: before-patch page_referenced-move-dirty 45.8 32.3 204.3 93.2 194.8 89.5 194.9 89.9 197.7 92.1 195.0 90.2 199.4 89.5 196.3 89.2 Numbers are seconds it took to dirty 1G of mmapped file on box with mem=64m (first row is different, because file was just created, and consists of one huge hole). Also I have seen that this patch improves oom-resistance on a box with small memory, all of which is dirtied through mmap. One possible explanation is that blk_congestion_wait() in try_to_free_pages() doesn't throttle scanner enough. > > > > > > > IOW: I'm gonna drop this one like it's made of lead! > > > > Let's decrease atomic number by 3. > > Still heavy. > Minus one more. Nikita. -- 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