From mboxrd@z Thu Jan  1 00:00:00 1970
From: fweisbec@gmail.com (Frederic Weisbecker)
Date: Thu, 14 Nov 2013 13:59:59 +0100
Subject: =?utf-8?B?562U5aSN?= =?utf-8?Q?=3A?= a bug on NO_HZ_FULL_ALL
In-Reply-To: <548C3FF8E9B1F945A9FEE3533A16C6CD4E9BF1DA@szxema507-mbs.china.huawei.com>
References: <CANHzE=2EOJmjFqLUDSfxTvgQhrUogOxH8Qux9hBFTGf8HiWWEw@mail.gmail.com>
 <52843855.5060509@linaro.org> <52847FBE.9070501@linaro.org>
 <CAKfTPtD7fo08mjQoLXMMDpyxQuyoCZLS33qBnnUcQEmzYai2VQ@mail.gmail.com>
 <52848547.9080604@linaro.org>
 <CANHzE=0yshUSnxRRhQ_hBjo8ze4pSzuWQq+SAWdosq+wdP8hFg@mail.gmail.com>
 <20131114115004.GB16501@localhost.localdomain>
 <548C3FF8E9B1F945A9FEE3533A16C6CD4E9BF1DA@szxema507-mbs.china.huawei.com>
Message-ID: <20131114125957.GA2637@localhost.localdomain>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Thu, Nov 14, 2013 at 12:39:24PM +0000, Sunshaojie wrote:
> Do you mean I must select CONFIG_NO_HZ_FULL_SYSIDLE option and merge the patch of "[PATCH] ARM: Support arch_irq_work_raise() via self IPIs"?

Yes you need to select CONFIG_NO_HZ_FULL_SYSIDLE=y. But latest linus tree should be fine
as it contains that patch.

Thanks.

> 
> -----????-----
> ???: Frederic Weisbecker [mailto:fweisbec at gmail.com] 
> ????: 2013?11?14? 19:50
> ???: Shaojie Sun
> ??: viresh kumar; Vincent Guittot; Alex Shi; Fathi Boudra; Guodong Xu; Amit Kucheria; Chris Redpath; Linaro Kernel; LAK; Kevin Hilman; Sunshaojie
> ??: Re: a bug on NO_HZ_FULL_ALL
> 
> On Thu, Nov 14, 2013 at 05:54:10PM +0800, Shaojie Sun wrote:
> > No, I think it is a bug.
> > 
> > Because I tested the option with NO_HZ_FULL and without 
> > NO_HZ_FULL_ALL. It had only little interruptes on CPU0 twd.
> > With same code, I added NO_HZ_FULL_ALL option. It had too many 
> > interruptes on CPU0 twd.
> 
> If you select:
> 
>    NO_HZ_FULL=y
>    NO_HZ_FULL_ALL=n
> 
> then you need to pass a nohz_full= cpu range in the boot parameter, otherwise it's simply going to behave like NO_HZ_FULL=n
> 
> OTOH, if you select NO_HZ_FULL_ALL=y, the "nohz_full=" parameter is not needed and all CPUs will be full dynticks except CPU 0 where you should see more tick than usual because it's handling the timekeeping for every other CPUs. Don't forget to select CONFIG_NO_HZ_FULL_SYSIDLE=y or CPU 0 will never shutdown its tick even if the entire system is idle.