From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752262Ab3KTIEr (ORCPT ); Wed, 20 Nov 2013 03:04:47 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:44899 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750858Ab3KTIEo (ORCPT ); Wed, 20 Nov 2013 03:04:44 -0500 Date: Wed, 20 Nov 2013 00:04:40 -0800 From: Christoph Hellwig To: Jens Axboe Cc: Dave Chinner , linux-kernel@vger.kernel.org Subject: Re: [Regression x2, 3.13-git] virtio block mq hang, iostat busted on virtio devices Message-ID: <20131120080440.GA13147@infradead.org> References: <20131119080218.GJ11434@dastard> <20131119201531.GA4094@kernel.dk> <20131119212042.GB4094@kernel.dk> <20131119213429.GQ11434@dastard> <528BDB97.8090608@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <528BDB97.8090608@kernel.dk> 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 Tue, Nov 19, 2013 at 02:43:51PM -0700, Jens Axboe wrote: > No, the nr_requests isn't actually relevant in the blk-mq context, the > driver sets its own depth. For the above, it's 64 normal commands, and 2 > reserved. The reserved would be for a flush, for instance. If someone > attempts to queue more than the allocated number of requests, it'll stop > the blk-mq queue and kick things into gear on the virtio side. Then when > requests complete, we start the queue again. Btw, any reason we lowerered the queue depth from 128 to 64 in virtio-blk?