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xen-devel
[Xen-devel] Re: [RFC PATCH V4 2/5] cpuidle: list based cpuidle driver re
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To: |
Trinabh Gupta <trinabh@xxxxxxxxxxxxxxxxxx> |
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Subject: |
[Xen-devel] Re: [RFC PATCH V4 2/5] cpuidle: list based cpuidle driver registration and selection |
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From: |
Len Brown <lenb@xxxxxxxxxx> |
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Date: |
Fri, 25 Mar 2011 03:05:36 -0400 (EDT) |
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venki@xxxxxxxxxx, ak@xxxxxxxxxxxxxxx, suresh.b.siddha@xxxxxxxxx, sfr@xxxxxxxxxxxxxxxx, peterz@xxxxxxxxxxxxx, benh@xxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxx, arjan@xxxxxxxxxxxxxxx |
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<20110322123208.28725.30945.stgit@xxxxxxxxxxxxxxxxxxx> <20110322123233.28725.92874.stgit@xxxxxxxxxxxxxxxxxxx> <alpine.LFD.2.02.1103222254420.10549@x980> <4D89BBDD.5090505@xxxxxxxxxxxxxxxxxx> <alpine.LFD.2.02.1103231633030.12911@x980> <4D8B5197.2060306@xxxxxxxxxxxxxxxxxx> |
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Alpine 2.02 (LFD 1266 2009-07-14) |
> I think there are other problems too, related to saving and restoring
> of pm_idle pointer. For example, cpuidle itself saves current value
> of pm_idle, flips it and then restores the saved value. There is
> no guarantee that the saved function still exists. APM does exact
> same thing (though it may not be used these days).
>
> The problem also is that a number of architectures have copied the
> same design based on pm_idle; so its spreading.
pm_idle is a primitive design yes, but I think the issue
with pm_idle is a theoretical one, at least on x86;
as there isn't any other code scribbling on pm_idle
in practice. So this is clean-up, rather than bug-fix work...
> > It isn't immediately clear to me that all of these options
> > need to be preserved.
>
> So what do you suggest can be removed?
I sent a series of small patches yesterday to get the ball rolling...
https://lkml.org/lkml/2011/3/24/54
I think the xen thing can go away.
I proposed that APM be removed entirely,
but that will take a few releases to conclude....
> > Are we suggesting that x86 must always build with cpuidle?
> > I'm sure that somebody someplace will object to that.
>
> Arjan argued that since almost everyone today runs cpuidle
> it may be best to include it in the kernel
> (https://lkml.org/lkml/2010/10/20/243). But yes, we agreed
> that we would have to make cpuidle lighter incrementally.
> Making ladder governor optional could be one way for example.
ladder is already optional.
cheers,
-Len Brown, Intel Open Source Technology Center
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