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 S1751782AbdJPG0V convert rfc822-to-8bit (ORCPT <rfc822;w@1wt.eu>);
        Mon, 16 Oct 2017 02:26:21 -0400
Received: from mout.gmx.net ([212.227.17.21]:64684 "EHLO mout.gmx.net"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1751382AbdJPG0U (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Mon, 16 Oct 2017 02:26:20 -0400
Message-ID: <1508135135.8087.17.camel@gmx.de>
Subject: Re: [RFC PATCH v2 4/8] tick/nohz: keep tick on for a fast idle
From: Mike Galbraith <efault@gmx.de>
To: "Li, Aubrey" <aubrey.li@linux.intel.com>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Aubrey Li <aubrey.li@intel.com>
Cc: tglx@linutronix.de, peterz@infradead.org, len.brown@intel.com,
        ak@linux.intel.com, tim.c.chen@linux.intel.com,
        linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
Date: Mon, 16 Oct 2017 08:25:35 +0200
In-Reply-To: <c64ed43d-8afe-7317-e31f-a7a5eef914d1@linux.intel.com>
References: <1506756034-6340-1-git-send-email-aubrey.li@intel.com>
         <1506756034-6340-5-git-send-email-aubrey.li@intel.com>
         <4523111.uMcC96MW3N@aspire.rjw.lan>
         <5beefd1a-2792-c371-3bb8-8ee2a6574020@linux.intel.com>
         <1508129104.8087.2.camel@gmx.de>
         <c64ed43d-8afe-7317-e31f-a7a5eef914d1@linux.intel.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:GEkDV1njZepsH+/FthPVlC6rIkrnRSJz8+oV+jsPa+yFFoGFOo3
 SFWmjnGxcdxfjcFfwwXStqx/BbnL2z7fTR+jT0/8PbwnioSVSZBo06o4x+nrLjahNPogFFd
 YL+SFihfNpZWIeeKthVqa7RvFpBhqBILPSSn66tYepmjogc3AM24HYv3UTUYwPre2UAu3Mx
 XRtj4TB1k9ci1cKyMwu3g==
X-UI-Out-Filterresults: notjunk:1;V01:K0:PBoD+ouFF5I=:dG5jWVGbgi2Zu25/gRESW4
 sF9Hid4UgRv3IeauXAaEP615TqQjlt6+UFBmZDhvJMtfSdhZWE+96jW6mczF9o3d+u1Lttclp
 sYjSudVUzs8nAhRxBX5DPS4MWPnrJYXE1M5YX0q4dtCvgXnMFzHE2nf0HRtHRBg9I7aSw2Oab
 LZ8mMqHvLsxF/L0uw52aPqHgjZcR+o6Xg18dkVT4m+fPXo7pz5YPPDr0xsqC1BhQj/pENaY8d
 M4mxML12f7zrvZcv0qsWgHMohQvlNEB43WytFMPIVmZWLwzJrf0F50supI8w+D5iHwDe/YDvP
 fcI5wYlx9aGm0nBTSdzJLCeNICmRLGEfRIKFvwhBslExdhAL5xPKTmPZBEl8qtjyMaJSmBrbf
 GfgnamNJ0Nlp2AaW0yS1P9xV12S2UZjmT9idGaqrhuW7/ytGCg+GbSKpBJWu9e4V1LEXk3YpQ
 q3sOc6XwGn7myul+JxTO2ZLm7tJl73C/yICafPnRgbBFO0dLExznSr99CYlYU98bWWfbagONo
 T5THdC5AAEddLjiO399PfpO4JWc8CIrRo0/WT9sf4qXkgrs4oR7F8n5Z8Ll2ipFFTjTWtY/5q
 Om3TMCgbyQT6Bh+Q5J2tAWHZvyNLOQUeWszSh4rzEGDWRY5ZibWyYsZgR0jCDKp7pTs979HOF
 VgLlRplVrDVceiQBP8enQKbObHoSfrHBmnbehznTz7rbdc4C8cYPlW6dhBjf1jKfylj7N9TSx
 /aYIZ75JTu933bIx5u1iAi/cUpkYrQ7/SHikLeitQgvSO+9vfLXMGY3VO3nYfFDoJtU/oIaxl
 JcSfGJ0CNBF3FHCl/4OJhgVD9go5XSa8L76l0FkJeeCAG8pRYw=
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, 2017-10-16 at 13:34 +0800, Li, Aubrey wrote:
> On 2017/10/16 12:45, Mike Galbraith wrote:
> > On Mon, 2017-10-16 at 11:26 +0800, Li, Aubrey wrote:
> >>
> >> I'll try to move quiet_vmstat() into the normal idle branch if this patch series
> >> are reasonable. Is fast_idle a good indication for it?
> > 
> > see x86_tip 62cb1188ed86 sched/idle: Move quiet_vmstate() into the NOHZ code
> 
> It looks like this commit makes tick stop critical as it can be invoked in interrupt
> exit path?

do_idle() ain't critical?  It is in my book.  Hopefully, you're about
to make that idle_stat.fast_idle thingy liberal enough that we cease
mucking about with the tick on every microscopic idle (and I can then
trash my years old local patch to avoid needlessly eating that cost).

	-Mike