Messages in this thread | | | Date | Fri, 14 Mar 2008 11:30:13 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: [patch 0/6] Guest page hinting version 6. |
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Zachary Amsden wrote: > On Thu, 2008-03-13 at 18:55 +0000, Hugh Dickins wrote: > >> On Thu, 13 Mar 2008, Jeremy Fitzhardinge wrote: >> >>> My other concern is just correctness over time on the Linux side. We already >>> have enough trouble keeping things like the pte and page structure state in >>> sync, with resulting rare data-loss bugs. Adding another layer which only >>> applies in specific environments raises the possibility for new bugs to be >>> un-noticed for a long time. How can we structure the VM changes to make sure >>> that its robust in the face of maintenance? >>> >> Yes, that's the main concern, as whenever lots of subtlety is added. >> I wonder if there's any chance of a CONFIG_DEBUG mode, which could be >> run on anybody's x86 machine, without involving any virtualization, but >> in which the PAGE_STATEs become essential to the correct working of the mm. >> > > How about a fake hypervisor, which is really just a random page evictor, > following the rules of CMM? >
Probably simpler to just have variants of the page_set_* functions which simulate the worst-possible host action immediately (ie, stealing pages, logically swapping them, etc). That wouldn't give you full coverage, but it would go some way. An async variant which schedules a change in a few milliseconds would help too.
I guess that's equivalent to having a special-purpose hypervisor built into the kernel (hm, sounds familiar...).
J
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