From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932486Ab1FVQEq (ORCPT ); Wed, 22 Jun 2011 12:04:46 -0400 Received: from mx1.fusionio.com ([66.114.96.30]:51980 "EHLO mx1.fusionio.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932301Ab1FVQEo (ORCPT ); Wed, 22 Jun 2011 12:04:44 -0400 X-ASG-Debug-ID: 1308758683-03d6a510a691ca0001-xx1T2L X-Barracuda-Envelope-From: JAxboe@fusionio.com Message-ID: <4E021297.4000505@fusionio.com> Date: Wed, 22 Jun 2011 18:04:39 +0200 From: Jens Axboe MIME-Version: 1.0 To: Vivek Goyal CC: Peter Zijlstra , Thomas Gleixner , "linux-kernel@vger.kernel.org" , Linus Torvalds , Ingo Molnar , Tejun Heo Subject: Re: [RFC][PATCH 1/3] sched, block: Move unplug References: <20110621233444.094372367@chello.nl> <20110621233648.806475812@chello.nl> <4E019353.6030902@fusionio.com> <4E01F5D6.1020107@fusionio.com> <1308753481.1022.27.camel@twins> <20110622150825.GE17010@redhat.com> X-ASG-Orig-Subj: Re: [RFC][PATCH 1/3] sched, block: Move unplug In-Reply-To: <20110622150825.GE17010@redhat.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Barracuda-Connect: mail1.int.fusionio.com[10.101.1.21] X-Barracuda-Start-Time: 1308758683 X-Barracuda-URL: http://10.101.1.180:8000/cgi-mod/mark.cgi X-Barracuda-Spam-Score: 0.00 X-Barracuda-Spam-Status: No, SCORE=0.00 using per-user scores of TAG_LEVEL=1000.0 QUARANTINE_LEVEL=1000.0 KILL_LEVEL=9.0 tests= X-Barracuda-Spam-Report: Code version 3.2, rules version 3.2.2.66807 Rule breakdown below pts rule name description ---- ---------------------- -------------------------------------------------- Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2011-06-22 17:08, Vivek Goyal wrote: > On Wed, Jun 22, 2011 at 04:38:01PM +0200, Peter Zijlstra wrote: >> On Wed, 2011-06-22 at 16:30 +0200, Thomas Gleixner wrote: >>>> It is supposedly a real problem, not just an inkling. It's not about >>>> recursing indefinitely, the plug is fairly bounded. But the IO dispatch >>>> path can be pretty deep, and if you hit that deep inside the reclaim or >>>> file system write path, then you get dangerously close. Dave Chinner >>>> posted some numbers in the 2.6.39-rc1 time frame showing how close we >>>> got. >>> >>> Fair enough. >> >>> Ok. So we move it out and keep the from_scheduler flag so that code >>> does not go down the IO path from there. >> >> Won't punting the plug to a worker thread wreck all kinds of io >> accounting due to the wrong task doing the actual io submission? > > I think all the accounting will the done in IO submission path and > while IO is added to plug. This is just plug flush so should not > have effect on accounting. Exactly, this is just the insert operation, so no worries there. The request are fully "formulated". -- Jens Axboe