Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750714AbWKFKlp (ORCPT ); Mon, 6 Nov 2006 05:41:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750890AbWKFKlp (ORCPT ); Mon, 6 Nov 2006 05:41:45 -0500 Received: from brick.kernel.dk ([62.242.22.158]:2894 "EHLO kernel.dk") by vger.kernel.org with ESMTP id S1750714AbWKFKlo (ORCPT ); Mon, 6 Nov 2006 05:41:44 -0500 Date: Mon, 6 Nov 2006 11:43:50 +0100 From: Jens Axboe To: Brent Baccala Cc: linux-kernel@vger.kernel.org Subject: Re: async I/O seems to be blocking on 2.6.15 Message-ID: <20061106104350.GR13555@kernel.dk> References: <20061103122055.GE13555@kernel.dk> <20061103160212.GK13555@kernel.dk> <20061105121522.GC13555@kernel.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1456 Lines: 38 On Mon, Nov 06 2006, Brent Baccala wrote: > On Sun, 5 Nov 2006, Jens Axboe wrote: > > >On Fri, Nov 03 2006, Brent Baccala wrote: > >> > >>Does 7 microseconds seem a bit excessive for an io_submit (and a > >>gettimeofday)? > > > >I guess you mean miliseconds, not microseconds. 7 miliseconds seems way > >too long. I repeated your test here, and the 100 submits take 97000 > >microseconds here - or 97 miliseconds. So that's a little less than 1 > >msec per io_submit. Still pretty big. You can experiment with oprofile > >to profile where the kernel spends its time in that period. > > > >-- > >Jens Axboe > > > > Yes, of course, milliseconds. I have enough other problems with this > program (measured in minutes, and no mistake that) that I doubt I'll > be profiling the kernel any time soon, but thank you for your help. > > More than anything else, you've made me understand that I can't just > fire off a bunch of async requests like I'm tossing peanuts across the > table. I've really got to pay attention to what's in that kernel > queue and how it gets managed. Yeah, I'm afraid so. We really should be returning EAGAIN or something like that for the congested condition, though. -- Jens Axboe - 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/