Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932109AbWBFNos (ORCPT ); Mon, 6 Feb 2006 08:44:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932089AbWBFNos (ORCPT ); Mon, 6 Feb 2006 08:44:48 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:8875 "EHLO ogre.sisk.pl") by vger.kernel.org with ESMTP id S932109AbWBFNor (ORCPT ); Mon, 6 Feb 2006 08:44:47 -0500 From: "Rafael J. Wysocki" To: Jens Axboe Subject: Re: Which is simpler? (Was Re: [Suspend2-devel] Re: [ 00/10] [Suspend2] Modules support.) Date: Mon, 6 Feb 2006 14:45:55 +0100 User-Agent: KMail/1.9.1 Cc: Pavel Machek , Nigel Cunningham , linux-kernel@vger.kernel.org, Suspend2 Devel List References: <20060201113710.6320.68289.stgit@localhost.localdomain> <20060206125253.GJ4101@elf.ucw.cz> <20060206130442.GV13598@suse.de> In-Reply-To: <20060206130442.GV13598@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200602061445.55966.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1567 Lines: 36 Hi, On Monday 06 February 2006 14:04, Jens Axboe wrote: > On Mon, Feb 06 2006, Pavel Machek wrote: > > > > I'll get same bandwidth as you, without need for async I/O. Async I/O > > > > is not really a feature, suspend speed is. (There are existing > > > > interfaces for doing AIO from userspace, anyway, but I'm pretty sure > > > > they will not be needed > > > > > > If you keep writing single pages sync, you sure as hell wont get > > > anywhere near async io in speed... > > > > well, we can perfectly do 128K block... just read 128K into userspace > > buffer, flush it via single write to block device. That should get us > > very close enough to media speed. > > That'll help naturally, 128k sync blocks will be very close to async > performance for most cases. Most cases here being drives with write back > caching enabled, if that is disabled async will still be a big win. > > Is there any reason _not_ to just go with async io? Usually the code is > just as simple (or simpler), since the in-kernel stuff is inherently > async to begin with. Actually the userland tools we're working on use async I/O. [There's no real need for sync, I think.] Still we write one page at a time, for now, so the I/O performance is not that much better than for the built-in swsusp, but it _is_ better. Greetings, Rafael - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/