From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751190AbdH0G5v convert rfc822-to-8bit (ORCPT <rfc822;w@1wt.eu>);
        Sun, 27 Aug 2017 02:57:51 -0400
Received: from mout.gmx.net ([212.227.15.15]:62827 "EHLO mout.gmx.net"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1750792AbdH0G5t (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Sun, 27 Aug 2017 02:57:49 -0400
Message-ID: <1503817025.7566.71.camel@gmx.de>
Subject: Re: [PATCH RFC/RFT] sched/fair: Improve the behavior of sync flag
From: Mike Galbraith <efault@gmx.de>
To: Joel Fernandes <joelaf@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>, Josef Bacik <jbacik@fb.com>,
        Juri Lelli <Juri.Lelli@arm.com>,
        Brendan Jackman <brendan.jackman@arm.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Matt Fleming <matt@codeblueprint.co.uk>,
        Rik van Riel <riel@redhat.com>, Ingo Molnar <mingo@redhat.com>
Date: Sun, 27 Aug 2017 08:57:05 +0200
In-Reply-To: <CAJWu+ooAPiuS+C7Gos4+8G9+DAvQL8X7=63D8U=yVLJkywbF7Q@mail.gmail.com>
References: <20170827010226.19703-1-joelaf@google.com>
         <1503812659.7566.43.camel@gmx.de>
         <CAJWu+ooAPiuS+C7Gos4+8G9+DAvQL8X7=63D8U=yVLJkywbF7Q@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
X-Mailer: Evolution 3.20.5 
Mime-Version: 1.0
Content-Transfer-Encoding: 8BIT
X-Provags-ID: V03:K0:H6LxTgP8cbm2Vh9e2/16NDMTdJI2eL0S+W+EKDichvN6+upxuvS
 ifSNI7CaEo/miEVS/d5IE1swnkXZn3azXy7ZbaieJhYdHXLdK+5e8YbaA6jXQ6i8/kC2VSc
 JJY2LgvA3i/1q7n6yFNNJs/L2bt5XjzTu6lY66fJFBqiQjVjYXhM9VRAdsF4IZvs2hVn8Mq
 U3YJks5wswnEQ1/CRl4kA==
X-UI-Out-Filterresults: notjunk:1;V01:K0:w5KxYEr2I/0=:oQ0OXSN06DQ32EbCHBE02R
 u+FRxz/0LjpozjIaVAszLUoqcfL7gN5sRP+O7we0nsFczN/eSrKQVYhx+43GWdYtppjc0Mte8
 Rr+TPXuSnnkw6qDFYF7QS+guEiJ3MaNhwtZeSVff0bys9ACwhNvt5hL0hKp3cFm8VrLna7mzO
 e0Vor8zqznq6IXbTZWDeefwXP9EeL0l0x5K79MF224mAOEQXPq6hfzwxTDAnkRS2qlNZImyB3
 uRdWEkjTYEHNC4kO596jdCfn2L4uWaZO2YHJzMvP1t2GD07DQSzPSG8iB20ov/7p6/XnLeL8c
 2M1kJKnSehgcOoVLXohcjhOJelCszMlrP4aoWNN0bZ0ACGrTDwqPpk2wDWZwAUMgqUZWbWT8C
 yWwiFi7qlm1bQpnbKyZ9TLPfeFP6UQWaCToM32YmPU2uevpxYc1AFo4JPHBTVy7/CXxWUzfvR
 tTRyAuo4FCCM+unoh5RzyNg+9V30NjA6qA70bvYysGn9w/tckB9uymDaobA8n+Uw8Ih/CAeMU
 RuIf14zVXNvM+bMmpIffsLz9g+mJ7ImgbfBG0l2PhcoyPquBDHyiTqBrwEyWY1ZLPcevkEl0C
 es94ZU4JXu4efLWz9duWPslM/N2ke8W/b7aBJa2TjkRKoq3rkrS12D8qfQv0GNQjt9HnZJnNX
 FgEsF9trwipT+VauXOqd20K6jH9UYjpxRm99DXVHViFUm5yIVIbqmDPDAmHEF3bqwEIrYM5Pd
 4LvIuYG9IDd0YyV5O0F7ihZVfshghUzVoA93KgcPX8ntnvxGZKiUHgj+KVKS4zS3SjBtHeiKq
 9Czt6Ud9xOcgixZqfK3YZ7u6s8uqJL5UFX0CsoFnUvek7EX3og=
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Sat, 2017-08-26 at 23:18 -0700, Joel Fernandes wrote:
> 
> > Sync is not a contract, it's a hint.  If you really want sync behavior,
> > you need to create a contract signed in blood to signal that you really
> > really are passing the baton.
> 
> Yes that is the usecase of binder, we are really passing the baton
> when we pass sync. We also make binder to not pass sync if there's
> more work todo and more tasks to wake up. In all current and past
> products, we have been using sync has a hard contract as you said.
> Are you proposing addition of another flag to differentiate between
> the existing hint and the contract?

Yes, the alternative being to unilaterally (as you did) make the
existing hint a contract, in which case you would get to deal with any
fallout.  You'd certainly get some "yay, you rock" mail, but you'd also
get some "boo, you suck rocks" to go with it :)

	-Mike