From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752600AbcFWNEk (ORCPT ); Thu, 23 Jun 2016 09:04:40 -0400 Received: from mail-wm0-f48.google.com ([74.125.82.48]:35013 "EHLO mail-wm0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932065AbcFWNEg (ORCPT ); Thu, 23 Jun 2016 09:04:36 -0400 Date: Thu, 23 Jun 2016 14:04:33 +0100 From: Matt Fleming To: Yuyang Du Cc: peterz@infradead.org, mingo@kernel.org, linux-kernel@vger.kernel.org, umgwanakikbuti@gmail.com, bsegall@google.com, pjt@google.com, morten.rasmussen@arm.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com Subject: Re: [RFC PATCH 08/11] sched: Remove SD_WAKE_AFFINE flag and replace it with SD_BALANCE_WAKE Message-ID: <20160623130433.GF8415@codeblueprint.co.uk> References: <1466041775-4528-1-git-send-email-yuyang.du@intel.com> <1466041775-4528-9-git-send-email-yuyang.du@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1466041775-4528-9-git-send-email-yuyang.du@intel.com> User-Agent: Mutt/1.5.24+41 (02bc14ed1569) (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 16 Jun, at 09:49:32AM, Yuyang Du wrote: > SD_BALANCE_{FORK|EXEC|WAKE} flags are for select_task_rq() to select a > CPU to run a new task or a waking task. SD_WAKE_AFFINE is a flag to > try selecting the waker CPU to run the waking task. > > SD_BALANCE_WAKE is not a sched_domain flag, but SD_WAKE_AFFINE is. > Conceptually, SD_BALANCE_WAKE should be a sched_domain flag just like > the other two, so we first make SD_BALANCE_WAKE a sched_domain flag. > > Moreover, the semantic of SD_WAKE_AFFINE is included in the semantic > of SD_BALANCE_WAKE. When in wakeup balancing, it is natual to try > the waker CPU if the waker CPU is allowed, in that sense, we don't > need a separate flag to specify it, not mentioning that SD_WAKE_AFFINE > is almost enabled in every sched_domains. > > With the above combined, there is no need to have SD_WAKE_AFFINE, so > we remove and replace it with SD_BALANCE_WAKE. This can be accomplished > without any functionality change. > > Signed-off-by: Yuyang Du > --- > include/linux/sched.h | 1 - > kernel/sched/core.c | 7 +++---- > kernel/sched/deadline.c | 2 +- > kernel/sched/fair.c | 9 ++++----- > kernel/sched/rt.c | 2 +- > 5 files changed, 9 insertions(+), 12 deletions(-) > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index d74e757..0803abd 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -1014,7 +1014,6 @@ extern void wake_up_q(struct wake_q_head *head); > #define SD_BALANCE_EXEC 0x0004 /* Balance on exec */ > #define SD_BALANCE_FORK 0x0008 /* Balance on fork, clone */ > #define SD_BALANCE_WAKE 0x0010 /* Balance on wakeup */ > -#define SD_WAKE_AFFINE 0x0020 /* Wake task to waking CPU */ > #define SD_SHARE_CPUCAPACITY 0x0080 /* Domain members share cpu power */ > #define SD_SHARE_POWERDOMAIN 0x0100 /* Domain members share power domain */ > #define SD_SHARE_PKG_RESOURCES 0x0200 /* Domain members share cpu pkg resources */ I'm curious - doesn't this break userspace ABI? These flags are exported via procfs, so I would have assumed removing or changing the value of any of these constants would be forbidden.