From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id EDEBA6B0218 for ; Wed, 17 Mar 2010 13:05:20 -0400 (EDT) Message-ID: <4BA10B66.1020705@redhat.com> Date: Wed, 17 Mar 2010 19:03:34 +0200 From: Avi Kivity MIME-Version: 1.0 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: owner-linux-mm@kvack.org 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 List-ID: 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org