Messages in this thread | | | Date | Tue, 13 Sep 2011 14:07:06 +0300 | From | Avi Kivity <> | Subject | Re: [PATCH v3 11/11] KVM: MMU: improve write flooding detected |
| |
On 08/30/2011 05:38 AM, Xiao Guangrong wrote: > Detecting write-flooding does not work well, when we handle page written, if > the last speculative spte is not accessed, we treat the page is > write-flooding, however, we can speculative spte on many path, such as pte > prefetch, page synced, that means the last speculative spte may be not point > to the written page and the written page can be accessed via other sptes, so > depends on the Accessed bit of the last speculative spte is not enough > > Instead of detected page accessed, we can detect whether the spte is accessed > after it is written, if the spte is not accessed but it is written frequently, > we treat is not a page table or it not used for a long time > >
The spte may not be accessed, but other sptes in the same page can be accessed. An example is the fixmap area for kmap_atomic(), there will be a lot of pte writes but other sptes will be accessed without going through soft-mmu at all.
I think you have to read the parent_ptes->spte.accessed bits to be sure.
-- error compiling committee.c: too many arguments to function
| |