From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756565AbaCON5Z (ORCPT ); Sat, 15 Mar 2014 09:57:25 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:46006 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755691AbaCON5Y (ORCPT ); Sat, 15 Mar 2014 09:57:24 -0400 Date: Sat, 15 Mar 2014 06:57:23 -0700 From: Christoph Hellwig To: "Theodore Ts'o" Cc: Linux Kernel Developers List , Venkatesh Srinivas , Rusty Russell , "Michael S. Tsirkin" , virtio-dev@lists.oasis-open.org, virtualization@lists.linux-foundation.org, Frank Swiderski Subject: Re: [PATCH] virtio-blk: make the queue depth the max supportable by the hypervisor Message-ID: <20140315135723.GA10475@infradead.org> References: <1394841445-16142-1-git-send-email-venkateshs@google.com> <1394854471-25700-1-git-send-email-tytso@mit.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1394854471-25700-1-git-send-email-tytso@mit.edu> User-Agent: Mutt/1.5.21 (2010-09-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 14, 2014 at 11:34:31PM -0400, Theodore Ts'o wrote: > The current virtio block sets a queue depth of 64, which is > insufficient for very fast devices. It has been demonstrated that > with a high IOPS device, using a queue depth of 256 can double the > IOPS which can be sustained. > > As suggested by Venkatash Srinivas, set the queue depth by default to > be one half the the device's virtqueue, which is the maximum queue > depth that can be supported by the channel to the host OS (each I/O > request requires at least two VQ entries). I don't think this should be a module parameter. The default sizing should be based of the parameters of the actual virtqueue, and if we want to allow tuning it it should be by a sysfs attribute, preferable using the same semantics as SCSI.