linux-kernel - Re: [RFC][PATCH] sched_clock

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Date:	Sun, 4 May 2008 11:00:25 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	David Miller <davem@...emloft.net>
Cc:	a.p.zijlstra@...llo.nl, tglx@...utronix.de, guichaz@...il.com,
	andi@...stfloor.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org, efault@....de,
	dhaval@...ux.vnet.ibm.com
Subject: Re: [RFC][PATCH] sched_clock_cpu()

* David Miller <davem@...emloft.net> wrote:

> > that wont work very well when sched_clock() is called from within 
> > CONFIG_LOCK_STAT instrumentation. Does the patch below solve the 
> > boot problems for you?
> 
> Also, no platform can set HAVE_STABLE_CLOCK until we instantiate it in 
> a Kconfig somewhere.  I've choosen to do it in kernel/Kconfig.hz and 
> here are the sparc/sparc64 bits as well, I've booted this up with 
> Peter's patch on my 64-cpu niagara2 box and done some basic testing.

applied, thanks David.

right now this topic looks good in review and in testing but it is 
stalled on a bug: in overnight testing it triggered an ftrace self-test 
hang that i bisected down to that patch. While that doesnt affect 
mainline it's something that shows that the new sched_clock() code is 
not as widely usable as the old code - have to investigate that some 
more.

> It would be nice if a powerpc person could test the trivial powerpc 
> Kconfig patch.
> 
> Possibly this should be HAVE_UNSTABLE_CLOCK, then only one platform 
> needs to set it :-)

heh, indeed :)

Initially i thought that it's better to first be safe, but this really 
will only affect x86 in practice, so ... i think we'll switch around the 
flag, turning this into a no-effort thing for everything but x86.

	Ingo
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