linux-kernel - Re: [GIT pull] Timer core updates for 4.16

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Message-ID: <alpine.DEB.2.20.1801301924370.1797@nanos>
Date:   Tue, 30 Jan 2018 19:25:31 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
cc:     Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>
Subject: Re: [GIT pull] Timer core updates for 4.16

On Tue, 30 Jan 2018, Linus Torvalds wrote:
> On Mon, Jan 29, 2018 at 10:30 PM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > These are in cases significant driver simplifications, but they also enable the
> > real deal, the elimination of the hrtimer tasklet:
> >
> >  softirq: Remove tasklet_hrtimer
> >
> >    include/linux/interrupt.h | 25 -----------------------
> >    kernel/softirq.c          | 51 -----------------------------------------------
> >    2 files changed, 76 deletions(-)
> >
> > ... which is a pretty nice thing in itself even without the driver
> > simplifications!
> >
> > Plus the _real_ secret motivation behind it all is the -rt kernel and
> > CONFIG_PREEMPT_RT=y and the ability to push most of the hrtimer processing into
> > softirq context - while it still keeps the main hrtimer machinery capable to run
> > in hard-RT hardirq domain. Turns out it was possible to implement this duality via
> > the softirq-hrtimers, with a good chunk of benefits to non-rt upstream as well.
> 
> So this is the kind of explanation that I would have liked in the
> "please pull" (and that would have been great in the merge message).
> Explaining not just the "what", but very much the "why".
> 
> Anyway, it's obviously pulled regardless, and I'm just pointing this
> out for "maybe next time".

Sorry about that. I usually try to be descriptive and will do so next time
again.

Thanks,

	tglx