linux-kernel - Re: nohz: Update tick instead of restarting tick in tick_nohz_idle

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Message-ID: <6d77dcc0-dea1-7b5e-9451-e4b21d7fb160@huawei.com>
Date:   Sat, 28 Nov 2020 08:32:05 +0800
From:   Yunfeng Ye <yeyunfeng@...wei.com>
To:     Frederic Weisbecker <frederic@...nel.org>
CC:     <fweisbec@...il.com>, <tglx@...utronix.de>, <mingo@...nel.org>,
        <linux-kernel@...r.kernel.org>, Shiyuan Hu <hushiyuan@...wei.com>,
        Hewenliang <hewenliang4@...wei.com>
Subject: Re: nohz: Update tick instead of restarting tick in
 tick_nohz_idle_exit()



On 2020/11/27 20:15, Frederic Weisbecker wrote:
> On Mon, Nov 23, 2020 at 09:22:08PM +0800, Yunfeng Ye wrote:
>> In realtime scenarios, the "nohz_full" parameter is configured. Tick
>> interference is not expected when there is only one realtime thread.
>> But when the idle thread is switched to the realtime thread, the tick
>> timer is restarted always.
>>
>> So on the nohz full mode, it is unnecessary to restart the tick timer
>> when there is only one realtime thread. Adding can_stop_full_tick()
>> before restarting the tick, if it return true, keep tick stopped.
>>
>> Signed-off-by: Yunfeng Ye <yeyunfeng@...wei.com>
> 
> We can indeed stop the tick and avoid it to be re-armed needlessly at this
> point.
> 
> I'm taking your patch, I may just edit it a little and resend it.
> 
Ok, thanks.

> Thanks!
> .
>