Re: [PATCH 11/11] KVM: MMU: improve write flooding detected

Marcelo Tosatti
2011-08-25T13:47:41Z

On Thu, Aug 25, 2011 at 07:42:10AM +0300, Avi Kivity wrote:
> On 08/25/2011 05:04 AM, Marcelo Tosatti wrote:
> >>
> >> It could increase the flood count independently of the accessed bit of
> >> the spte being updated, zapping after 3 attempts as it is now.
> >>
> >> But additionally reset the flood count if the gpte appears to be valid
> >> (points to an existant gfn if the present bit is set, or if its zeroed).
> >
> >Well not zero, as thats a common pattern for non ptes.
> >
>
> On 32-bit with 4GB RAM, practically anything is a valid gpte.

The following could be required to consider a valid gpte, for write
flood detection purposes:

- Must be present.
- PageCacheDisable must be unset.
- PageWriteThrough must be unset.