From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754895Ab0CQRFk (ORCPT ); Wed, 17 Mar 2010 13:05:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:22244 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754246Ab0CQRFi (ORCPT ); Wed, 17 Mar 2010 13:05:38 -0400 Message-ID: <4BA10B66.1020705@redhat.com> Date: Wed, 17 Mar 2010 19:03:34 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.8) Gecko/20100301 Fedora/3.0.3-1.fc12 Thunderbird/3.0.3 MIME-Version: 1.0 To: Christoph Hellwig CC: Chris Webb , balbir@linux.vnet.ibm.com, KVM development list , Rik van Riel , KAMEZAWA Hiroyuki , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Kevin Wolf Subject: Re: [PATCH][RF C/T/D] Unmapped page cache control - via boot parameter References: <4B9DE635.8030208@redhat.com> <20100315080726.GB18054@balbir.in.ibm.com> <4B9DEF81.6020802@redhat.com> <20100315202353.GJ3840@arachsys.com> <4B9F4CBD.3020805@redhat.com> <20100317152452.GZ31148@arachsys.com> <4BA101C5.9040406@redhat.com> <4BA105FE.2000607@redhat.com> <20100317164752.GA31884@arachsys.com> <4BA1090E.9090502@redhat.com> <20100317165854.GC29548@lst.de> In-Reply-To: <20100317165854.GC29548@lst.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/17/2010 06:58 PM, Christoph Hellwig wrote: > On Wed, Mar 17, 2010 at 06:53:34PM +0200, Avi Kivity wrote: > >> Meanwhile I looked at the code, and it looks bad. There is an >> IO_CMD_FDSYNC, but it isn't tagged, so we have to drain the queue before >> issuing it. In any case, qemu doesn't use it as far as I could tell, >> and even if it did, device-matter doesn't implement the needed >> ->aio_fsync() operation. >> > No one implements it, and all surrounding code is dead wood. It would > require us to do asynchronous pagecache operations, which involve > major surgery of the VM code. Patches to do this were rejected multiple > times. > Pity. What about the O_DIRECT aio case? It's ridiculous that you can submit async write requests but have to wait synchronously for them to actually hit the disk if you have a write cache. -- error compiling committee.c: too many arguments to function