linux-kernel - Re: your mail

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Date:   Wed, 16 Nov 2016 09:25:43 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Christoph Lameter <cl@...ux.com>, Daniel Vacek <neelx.g@...il.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Tommaso Cucinotta <tommaso.cucinotta@...up.it>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: your mail

On Wed, 16 Nov 2016 11:40:14 +0100
Peter Zijlstra <peterz@...radead.org> wrote:

> On top of which, the implementation had issues; now I know you're the
> blinder kind of person that disregards everything not in his immediate
> interest, but if you'd looked at the patch you'd have seen he'd added
> code the idle entry path, which will slow down every single to-idle
> transition.

Isn't to-idle a bit bloated anyway? Or has that been fixed. I know
there was some issues with idle_balance() which can add latency to
wakeups. idle_balance() is also in the to-idle path.

Note, that this is a sched feature which would be a nop (jump_label)
when disabled. And I'm sure it could also be optimized to be a static
inline as well when it is enabled.

I'm not saying we need to go this approach, but I'm just saying that
the to-idle issue is a bit of a red herring.

-- Steve