From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH 7/8] lguest: trivial guest block driver Date: Mon, 12 Feb 2007 16:01:25 +0100 Message-ID: <20070212150125.GM3999@kernel.dk> References: <1171251965.10409.28.camel@localhost.localdomain> <1171252113.10409.30.camel@localhost.localdomain> <1171252219.10409.33.camel@localhost.localdomain> <1171252321.10409.36.camel@localhost.localdomain> <1171252405.10409.39.camel@localhost.localdomain> <1171252474.10409.42.camel@localhost.localdomain> <20070212044339.GJ3685@kernel.dk> <1171258034.10409.54.camel@localhost.localdomain> <20070212053204.GB3999@kernel.dk> <1171264167.10409.62.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1171264167.10409.62.camel@localhost.localdomain> Sender: linux-kernel-owner@vger.kernel.org To: Rusty Russell Cc: Andrew Morton , lkml - Kernel Mailing List , virtualization List-Id: virtualization@lists.linuxfoundation.org On Mon, Feb 12 2007, Rusty Russell wrote: > On Mon, 2007-02-12 at 06:32 +0100, Jens Axboe wrote: > > On Mon, Feb 12 2007, Rusty Russell wrote: > > > On Mon, 2007-02-12 at 05:43 +0100, Jens Axboe wrote: > > > > Here you map the entire request (lets call that segment A..Z), but > > > > end_request() only completes the first chunk of the request. So > > > > elv_next_request() will retrieve the same request again, and you'll then > > > > map B..Z and repeat that transfer. So unless I'm missing some other part > > > > here (just read it over quickly), you are re-doing large parts of a > > > > merged request several times. > > virtbench before: > Time to read from disk (256 kB): 18654562 nsec > After: > Time to read from disk (256 kB): 8018468 nsec > > Thanks Jens!! My pleasure, it's not often you get to make that big a performance improvement with just a little few lines of change :-) I guess you'll take changes to make this driver queuing as well? It's pretty important for good guest io performance as well. -- Jens Axboe