linux-kernel - Re: various laptop nagles - any suggestions? (note: 2.6.19-rc2-mm1 but applies to multiple kernels)

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Date:	Sat, 21 Oct 2006 16:52:59 +0200
From:	Arjan van de Ven <arjan@...radead.org>
To:	Andrew Morton <akpm@...l.org>
Cc:	tglx@...utronix.de, teunis <teunis@...tersgift.com>,
	linux-kernel@...r.kernel.org, Dmitry Torokhov <dtor@...l.ru>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: various laptop nagles - any suggestions?   (note:
	2.6.19-rc2-mm1 but applies to multiple kernels)

On Fri, 2006-10-20 at 11:26 -0700, Andrew Morton wrote:
> On Fri, 20 Oct 2006 20:13:54 +0200
> Thomas Gleixner <tglx@...utronix.de> wrote:
> 
> > > Also, NO_HZ breaks my laptop (and presumably quite a few others) quite
> > > horridly, which means nobody can ship the feature.  Some runtime
> > > turn-it-off work needs to be done there.
> > 
> > We can make a commandline switch as for highres. Is that sufficient ?
> 
> I doubt it.
> 
> I don't know how many machines will be affected by this, but I'd expect
> it's quite a few - the Vaio has a less-than-one-year-old Intel CPU in it.
> 
> I'd expect that if a distro were to enable NO_HZ, they'd have a large
> number of unhappy users whose machines run like crap, some of whom would
> find out that they need to add some funny dont-run-like-crap option and
> some of whom would, after wasting considerable amounts of time, just give
> up and use windows or RH5.2 or something.


well NO_HZ as is is incompatible with any machine which has support for
the C3 state (at least if they have an Intel CPU) since the local apic
timer just plain stops in C3 unfortunately.

We really need to think about using HPET for this, and potentially on a
single socket system, not do per core timer queues but just 1 global
timer queue. 


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