From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 0/6][RFC] virtio-blk: Change I/O path from request to BIO Date: Mon, 2 Jan 2012 11:18:03 -0500 Message-ID: <20120102161803.GA32365@infradead.org> References: <1324429254-28383-1-git-send-email-minchan@kernel.org> <20111222234135.GB7056@barrios-laptop.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Minchan Kim , Rusty Russell , Chris Wright , Jens Axboe , Stefan Hajnoczi , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig , Vivek Goyal To: Stefan Hajnoczi Return-path: Received: from 173-166-109-252-newengland.hfc.comcastbusiness.net ([173.166.109.252]:53392 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752728Ab2ABQSK (ORCPT ); Mon, 2 Jan 2012 11:18:10 -0500 Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On Sun, Jan 01, 2012 at 04:45:42PM +0000, Stefan Hajnoczi wrote: > win. The fact that you added batching suggests there is some benefit > to what the request-based code path does. So find out what's good > about the request-based code path and how to get the best of both > worlds. Batching pretty much always is a winner. The maximum bio size is small enough that we'll frequently see multiple contiguos bios. Because of that the Md layer fo example uses the same kind of batching. I've tried to make this more general by passing a bio list to ->make_request and make the on-stack plugging work on bios, but in the timeslice I had available for that I didn't manage to actually make it work.