Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754039Ab0KHCH2 (ORCPT ); Sun, 7 Nov 2010 21:07:28 -0500 Received: from mga14.intel.com ([143.182.124.37]:24182 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753174Ab0KHCHV (ORCPT ); Sun, 7 Nov 2010 21:07:21 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.58,311,1286175600"; d="scan'208";a="345726687" Subject: [patch 2/3]cfq-iosched: schedule dispatch for noidle queue From: Shaohua Li To: lkml Cc: Jens Axboe , vgoyal@redhat.com, czoccolo@gmail.com Content-Type: text/plain; charset="UTF-8" Date: Mon, 08 Nov 2010 10:07:18 +0800 Message-ID: <1289182038.23014.190.camel@sli10-conroe> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2184 Lines: 63 A queue is idle at cfq_dispatch_requests(), but it gets noidle later. Unless other task explictly does unplug or all requests are drained, we will not deliever requests to the disk even cfq_arm_slice_timer doesn't make the queue idle. For example, cfq_should_idle() returns true because of service_tree->count == 1, and then other queues are added. Note, I didn't see obvious performance impacts so far with the patch, but just thought this could be a problem. Signed-off-by: Shaohua Li --- block/cfq-iosched.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) Index: linux/block/cfq-iosched.c =================================================================== --- linux.orig/block/cfq-iosched.c 2010-11-08 08:41:20.000000000 +0800 +++ linux/block/cfq-iosched.c 2010-11-08 08:43:51.000000000 +0800 @@ -3265,6 +3265,10 @@ cfq_should_preempt(struct cfq_data *cfqd if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq)) return true; + /* An idle queue should not be idle now for some reason */ + if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq)) + return true; + if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq)) return false; @@ -3508,8 +3512,25 @@ static void cfq_completed_request(struct } } - if (!cfqd->rq_in_driver) + if (!cfqd->rq_in_driver) { cfq_schedule_dispatch(cfqd); + return; + } + /* + * A queue is idle at cfq_dispatch_requests(), but it gets noidle + * later. We schedule a dispatch if the queue has no requests, + * otherwise the disk is actually in idle till all requests + * are finished even cfq_arm_slice_timer doesn't make the queue idle + * */ + cfqq = cfqd->active_queue; + if (!cfqq) + return; + + if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq) && + (!cfqd->cfq_group_idle || cfqq->cfqg->nr_cfqq > 1)) { + cfq_del_timer(cfqd, cfqq); + cfq_schedule_dispatch(cfqd); + } } /* -- 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/