From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: Re: Page Cache writeback too slow, SSD/noop scheduler/ext2 Date: Tue, 31 Mar 2009 20:31:12 +0800 Message-ID: <20090331123112.GA15098@localhost> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Nick Piggin , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Jeff Layton , Dave Chinner , "linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "jens.axboe-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org" , "akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org" , "hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org" , "linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" To: Jos Houtman Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-nfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org On Tue, Mar 31, 2009 at 08:16:52PM +0800, Jos Houtman wrote: > > > > Next to that I was wondering if there are any plans to make sure that not > > all dirty-files are written back in the same interval. > > > > In my case all database files are written back each 30 seconds, while I > > would prefer them to be more divided over the interval. > > There another question I have: does the writeback go through the io > scheduler? Because no matter the io scheduler or the tuning done, the > writeback algorithm totally starves the reads. I noticed this annoying writes-starve-reads problem too. I'll look into it. > See the url below for an example with CFQ, but deadline or noop all show > this behaviour: > http://94.100.113.33/535450001-535500000/535451701-535451800/535451800_6_L7g > t.jpeg > > Is there anything I can do about this behaviour by creating a better > interleaving of the reads and writes? I guess it should be handled in the generic block io layer. Once we solved the writes-starve-reads problem, the bursty-writeback behavior becomes a no-problem for SSD. Thanks, Fengguang -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html