Re: [RFC] respect the referenced bit of KVM guest pages?

From: Rik van Riel
Date: Wed Aug 05 2009 - 13:26:28 EST


Andrea Arcangeli wrote:
On Wed, Aug 05, 2009 at 10:15:16AM -0400, Rik van Riel wrote:
Not having a hardware accessed bit would explain why
the VM is not reactivating the pages that were accessed
while on the inactive list.

Problem is, even with young bit functional the VM isn't reactivating
those pages anyway because of that broken check...

That check is only done where active pages are moved to the
inactive list! Inactive pages that were referenced always
get moved to the active list (except for unmapped file pages).

I think it'll still better than current situation, as young bit is
always set for ptes. Otherwise EPT pages are too penalized, we need
them to stay one round more in active list like everything else.

NOTHING ELSE stays on the active anon list for two rounds,
for very good reasons. Please read up on what has changed
in the VM since 2.6.27.

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