Il 16/05/2013 14:43, Gleb Natapov ha scritto:
>> > +restart:
>> > + list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) {
>> > + if (!is_obsolete_sp(kvm, sp))
>> > + continue;
> What if we save kvm->arch.active_mmu_pages on the stack and init
> kvm->arch.active_mmu_pages to be empty at the entrance to
> zap_invalid_pages(). This loop will iterate over saved list. This will
> allow us to drop the is_obsolete_sp() check and will save time since we
> will not be iterating over newly created sps.
>
But when you add cond_resched_lock a thread may want to zap pages itself
(e.g. from prepare_zap_oldest_mmu_page) and it won't find them.
Here is another proposal... The idea is to avoid looking at new pages
more than necessary after a "goto restart".
Basically, you alternate between two phases:
- look for pages to be zapped, group them together
- zap the pages
Something like:
moved = 0;
restart:
zapping = true;
for each page in active_mmu_pages [reverse and safe] {
if (!is_obsolete || invalid) {
/*
* Found a new page, stop zapping for now and
* try to segregate the invalid ones at one end
* of the list.
*/
zapping = false;
continue;
}
if (batch > 10 && ...) {
cond_resched_lock
batch = 0;
goto restart;
}
if (!zapping) {
/*
* Segregate pages to one end of the list where
* new pages don't get in the way.
*/
list_move_tail(page, active_mmu_pages)
batch++; /* or maybe not? */
moved++;
} else {
batch += prepare_zap_page
goto restart;
}
}
/* Need another pass to look at segregated pages? */
if (moved) {
moved = 0;
goto restart;
}
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