linux-kernel - Re: [PATCH 2/5] x86: remove idle

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Message-ID: <alpine.DEB.2.20.1612081014280.3400@nanos>
Date:   Thu, 8 Dec 2016 10:18:13 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Pavel Machek <pavel@....cz>
cc:     Len Brown <lenb@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 2/5] x86: remove idle_notifier

On Wed, 7 Dec 2016, Pavel Machek wrote:
> On Wed 2016-12-07 12:46:12, Thomas Gleixner wrote:
> > On Tue, 6 Dec 2016, Pavel Machek wrote:
> > > > From: Len Brown <len.brown@...el.com>
> > > > 
> > > > Upon removal of the i7300_idle driver, the idle_notifer is unused.
> > > 
> > > Actually... do we want to keep this this one? There's "cpu is loaded"
> > > led trigger, which is implemented on arm but not on x86.
> > > 
> > > I tried to patch process.c, but this would be easier (and does not
> > > require new hooks).
> > > 
> > > Does that make sense?
> > 
> > No. Notifiers are crap.
> > 
> > I assume this LED thing is just for entertainment purposes as I cannot
> > figure out why it would be useful. ARM has it does not qualify as useful.
> 
> Well, on low-speed systems, that led is actually quite important. You
> know if your keypress was registered, and CPU is just slow, or if you
> need to press it again.

I'm dealing with low-speed systems for 20 years now and that LED was never
important for me, quite the contrary, it's annoying to have the extra work
in the idle wakeup path which causes extra pointless latency. If you can't
figure out your keypress lag without that LED then feel free to patch your
own kernel, but stop trying to impose that nonsense on everyone.

Thanks,

	tglx