From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754330AbdHYBsD (ORCPT ); Thu, 24 Aug 2017 21:48:03 -0400 Received: from mail.kernel.org ([198.145.29.99]:34492 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753924AbdHYBsC (ORCPT ); Thu, 24 Aug 2017 21:48:02 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3CA0521A1B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Thu, 24 Aug 2017 21:47:59 -0400 From: Steven Rostedt To: Byungchul Park Cc: peterz@infradead.org, mingo@kernel.org, joel.opensrc@gmail.com, linux-kernel@vger.kernel.org, juri.lelli@gmail.com, kernel-team@lge.com Subject: Re: [PATCH v10 2/2] sched/rt: Add support for SD_PREFER_SIBLING on find_lowest_rq() Message-ID: <20170824214759.441e5fcf@gandalf.local.home> In-Reply-To: <20170825013100.GC3858@X58A-UD3R> References: <1503536763-14912-1-git-send-email-byungchul.park@lge.com> <1503536763-14912-3-git-send-email-byungchul.park@lge.com> <20170824095514.48222762@gandalf.local.home> <20170825013100.GC3858@X58A-UD3R> X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 25 Aug 2017 10:31:00 +0900 Byungchul Park wrote: > On Thu, Aug 24, 2017 at 09:55:14AM -0400, Steven Rostedt wrote: > > On Thu, 24 Aug 2017 10:06:03 +0900 > > Byungchul Park wrote: > > > > > Hello Steven, > > > > > > Can I keep your reviewed-by with comments modified? > > > > Yes, but I have one nit. > > > > > > > @@ -1668,9 +1691,35 @@ static int find_lowest_rq(struct task_struct *task) > > > return this_cpu; > > > } > > > > > > - best_cpu = cpumask_first_and(lowest_mask, > > > - sched_domain_span(sd)); > > > + /* > > > + * If a cpu being in lowest_mask & current sd & > > > + * ~prefer sd is valid, that becomes our choice. > > > > I can't parse the above sentence. > > I might have simplified the comment too much. > > ~prefer means we want to exclude the domain span having SD_PREFER_SIBLING, > since they should be considered as fallback candidates. > > W/o ~prefer, a cpu in the domain might be chosen when we consider higher > domain than the domain having SD_PREFER_SIBLING, as the best cpu, not > fallback. That actually wasn't the hard part. It was the entire sentence that is very confusing. What is the definition of "is valid" in this context? Do you just mean "< nr_cpu_ids"? If that's the case you are also being redundant. Because if the "if" statement is true, then it will be valid. What about just saying something like: /* * If a cpu exists that is in the lowest_mask and the current sd span, * but not in the prefer sd span, then that becomes our choice. */ -- Steve