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 09:58:05 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
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>,
        Quan Xu <quan.xu0@...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 Thu, 16 Nov 2017, 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.

That's why I said: But lets not proliferate that. I'd rather see that go
away.

And yes, the VM folks should talk to those who are trying to solve similar
problems for native (embedded/mobile).

Thanks,

	tglx