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

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Message-ID: <20171116084555.it2hqajxxd6ld5tq@hirez.programming.kicks-ass.net>
Date:   Thu, 16 Nov 2017 09:45:55 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     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>,
        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 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.