From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758433Ab1JFNxM (ORCPT ); Thu, 6 Oct 2011 09:53:12 -0400 Received: from 87-104-106-3-dynamic-customer.profibernet.dk ([87.104.106.3]:43279 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753720Ab1JFNxL (ORCPT ); Thu, 6 Oct 2011 09:53:11 -0400 Date: Thu, 6 Oct 2011 15:53:09 +0200 From: Jens Axboe To: Christoph Hellwig Cc: Rusty Russell , Chris Wright , Stefan Hajnoczi , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 5/5] virtio-blk: implement ->make_request Message-ID: <20111006135309.GA27941@kernel.dk> References: <20111005195403.407628164@bombadil.infradead.org> <20111005195530.558142038@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111005195530.558142038@bombadil.infradead.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 05 2011, Christoph Hellwig wrote: > Add an alternate I/O path that implements ->make_request for virtio-blk. > This is required for high IOPs devices which get slowed down to 1/5th of > the native speed by all the locking, memory allocation and other overhead > in the request based I/O path. We definitely have some performance fruit hanging rather low in that path, but a factor 5 performance difference sounds insanely excessive. I haven't looked at virtio_blk in detail, but I've done 500K+ IOPS on request based drivers before (yes, on real hardware). So it could be that virtio_blk is just doing things rather suboptimally in some places, and that it would be possible to claim most of that speedup there too. -- Jens Axboe