From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool Date: Thu, 11 Dec 2008 14:40:29 -0600 Message-ID: <49417ABD.6020908@codemonkey.ws> References: <493FFAB6.2000106@codemonkey.ws> <493FFC8E.9080802@redhat.com> <49400F69.8080707@codemonkey.ws> <20081210190810.GG18814@random.random> <20081211131222.GA14908@random.random> <494130B5.2080800@redhat.com> <20081211155335.GE14908@random.random> <49413B9C.3030703@redhat.com> <20081211164947.GD6809@random.random> <49414BC9.5090905@redhat.com> <20081211181116.GE6809@random.random> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Gerd Hoffmann , kvm-devel , qemu-devel@nongnu.org To: Andrea Arcangeli Return-path: Received: from yx-out-2324.google.com ([74.125.44.28]:57725 "EHLO yx-out-2324.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758119AbYLKUkh (ORCPT ); Thu, 11 Dec 2008 15:40:37 -0500 Received: by yx-out-2324.google.com with SMTP id 8so558549yxm.1 for ; Thu, 11 Dec 2008 12:40:36 -0800 (PST) In-Reply-To: <20081211181116.GE6809@random.random> Sender: kvm-owner@vger.kernel.org List-ID: Andrea Arcangeli wrote: > On Thu, Dec 11, 2008 at 06:20:09PM +0100, Gerd Hoffmann wrote: > >> Andrea Arcangeli wrote: >> >>> On Thu, Dec 11, 2008 at 05:11:08PM +0100, Gerd Hoffmann wrote: >>> >>>> Yes. But kernel aio requires O_DIRECT, so aio users are affected >>>> nevertheless. >>>> >>> Are you sure? It surely wasn't the case... >>> >> Tons of docs say so, but might be they are wrong, I didn't check. >> > > I guess those tons of docs are just wrong then ;). I see no mention of > O_DIRECT in `man io_submit` at least... io_submit blocks unless you use O_DIRECT for most filesystems that people care about. This is why the current trends are toward kernel space thread pools. It would be very difficult to modify every file system to support true asynchronous buffered IO. Also, it's pretty clear that linux-aio doesn't have a strong future so I don't think it's very worthwhile to support. Regards, Anthony Liguori Regards, Anthony Liguori