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

Avi Kivity
2011-08-25T14:07:28Z

On 08/25/2011 05:06 PM, Avi Kivity wrote:
> On 08/25/2011 04:21 PM, Marcelo Tosatti wrote:
>> 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.
>>
>
> Unless the guest is using PAT.
>

And not swapping.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.