linux-kernel - Re: [PATCH RFC v3 3/6] sched/idle: Add a generic poll before enter real idle path

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Date:   Thu, 16 Nov 2017 17:29:58 +0800
From:   Quan Xu <quan.xu0@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Quan Xu <quan.xu03@...il.com>, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org, x86@...nel.org,
        xen-devel@...ts.xenproject.org,
        Yang Zhang <yang.zhang.wz@...il.com>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Kyle Huey <me@...ehuey.com>, Len Brown <len.brown@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Tobias Klauser <tklauser@...tanz.ch>,
        Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH RFC v3 3/6] sched/idle: Add a generic poll before enter
 real idle path



On 2017-11-16 16:45, Peter Zijlstra wrote:
> On Wed, Nov 15, 2017 at 11:03:08PM +0100, Thomas Gleixner wrote:
>> If I understand the problem correctly then he wants to avoid the heavy
>> lifting in tick_nohz_idle_enter() in the first place, but there is already
>> an interesting quirk there which makes it exit early.
> Sure. And there are people who want to do the same for native.
>
> Adding more ugly and special cases just isn't the way to go about doing
> that.
>
> I'm fairly sure I've told the various groups that want to tinker with
> this to work together on this. I've also in fairly significant detail
> sketched how to rework the idle code and idle predictors.
>
> At this point I'm too tired to dig any of that up, so I'll just keep
> saying no to patches that don't even attempt to go in the right
> direction.
Peter, take care.

I really have considered this factor, and try my best not to interfere 
with scheduler/idle code.
if irq_timings code is ready, I can use it directly. I think irq_timings 
is not an easy task, I'd
like to help as much as I can.  Also don't try to touch tick_nohz* code 
again.

as tglx suggested, this can be handled either in a HV specific idle driver or even in the generic core code.

I hope this is in the right direction.

Quan
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