From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932358Ab2CUBlE (ORCPT ); Tue, 20 Mar 2012 21:41:04 -0400 Received: from mail-qa0-f53.google.com ([209.85.216.53]:55406 "EHLO mail-qa0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757620Ab2CUBlC (ORCPT ); Tue, 20 Mar 2012 21:41:02 -0400 Date: Wed, 21 Mar 2012 09:40:50 +0800 From: Yong Zhang To: "Michael J. Wang" Cc: "mingo@elte.hu" , "peterz@infradead.org" , "linux-kernel@vger.kernel.org" , "rostedt@goodmis.org" Subject: Re: [PATCH 1/1] scheduler: minor improvement to pick_next_highest_task_rt in linux-3.3 Message-ID: <20120321014050.GA19766@zhy> Reply-To: Yong Zhang References: <2EF88150C0EF2C43A218742ED384C1BC0FC83D6B@IRVEXCHMB08.corp.ad.broadcom.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <2EF88150C0EF2C43A218742ED384C1BC0FC83D6B@IRVEXCHMB08.corp.ad.broadcom.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 19, 2012 at 10:26:19PM +0000, Michael J. Wang wrote: > From: Michael J Wang > > Avoid extra work by continuing on to the next rt_rq if the highest prio task in current rt_rq is the same priority as our candidate task. > > Signed-off-by: Michael J Wang > > --- > > More detailed explanation: if next is not NULL, then we have found a candidate task, and its priority is next->prio. Now we are looking for an even higher priority task in the other rt_rq's. idx is the highest priority in the current candidate rt_rq. In the current 3.3 code, if idx is equal to next->prio, we would start scanning the tasks in that rt_rq and replace the current candidate task with a task from that rt_rq. But the new task would only have a priority that is equal to our previous candidate task, so we have not advanced our goal of finding a higher prio task. So we should avoid the extra work by continuing on to the next rt_rq if idx is equal to next->prio. > You should limit characters of each line to 80 if possible. And before sending you patch, linux-source/scripts/checkpatch.pl maybe give you some clues whether there is some warning/error. If there are, fix them. Only for what your patch wants to show: Reviewed-by: Yong Zhang Thanks, Yong > --- linux-3.3/kernel/sched/rt.c.orig 2012-03-18 16:15:34.000000000 -0700 > +++ linux-3.3/kernel/sched/rt.c 2012-03-19 14:52:54.585391702 -0700 > @@ -1403,7 +1403,7 @@ static struct task_struct *pick_next_hig > next_idx: > if (idx >= MAX_RT_PRIO) > continue; > - if (next && next->prio < idx) > + if (next && next->prio <= idx) > continue; > list_for_each_entry(rt_se, array->queue + idx, run_list) { > struct task_struct *p; > > > > > > > -- > 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/ -- Only stand for myself