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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: |
Vaidyanathan Srinivasan <svaidy@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 03:13:04 -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, Trinabh Gupta <trinabh@xxxxxxxxxxxxxxxxxx> |
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Alpine 2.02 (LFD 1266 2009-07-14) |
> > So what do you suggest can be removed?
>
> Can we use safe_halt() until intel_idle/acpi_idle take over? But what
> if they do not take over? If safe_halt() is not very bad compared to
> the variants like mwait_idle and c1e_idle, then we can remove the old
> code and no need to move them to default driver.
One reason I'd like a default cpuidle driver is that today
there is a race. cpuidle registers, but until its driver
registers it will use polling. go ahead and look:
grep . /sys/devices/system/cpu/cpu*/cpuidle/state0/usage
that should be 0, but it isn't...
> > >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.
> > >
> > >OTOH, if cpuidle is included, I'd like to see the
> > >non-cpuidle code excluded, since nobody will run it...
>
> The non-cpuidle code will be the select_idle_routine() and related
> function that cam move to default_driver that register to cpuidle.
> We can load on-demand as module if better routines fail to register.
> Maybe we don't need this at all as discussed in the above point?
Right, though I don't share your fascination with modules.
cheers,
Len Brown, Intel Open Source Technology Center
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