[Xen-devel] Re: [PATCH] Align periodic vpts

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 11/02/2009 11:05, "Wei, Gang" <gang.wei@xxxxxxxxx> wrote:

> Aligned periodic vpts can improve the HVM guest power consumption a lot,
> especially while the guest using high HZ such as 1000HZ.
> This patch aligns all periodic vpts except vlapic to the period bound. For
> vlapic, only make it aligned while using the new option "align_periodic_vpt".
> 
> Signed-off-by: Wei Gang <gang.wei@xxxxxxxxx>

Also, Intel already contributed code to merge up timers. It's the
expiry-range patch in common/timer.c. This could be used by vpt.c to add a
per-domain acceptable range on vpt expiries. High-frequency timers would
then naturally fire together. Having a per-domain config option for this
would be something that would actually seem more generically useful (could
be used perhaps for other timers beyond vpt.c even).

This seems to me a more intuitive and gracefully selectable/de-selectable
alternative to this proposed patch, which really looks like a hardcoded
hack.

 -- Keir



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