Now that the fast invalidate mechanism has been reintroduced, restore
the performance tweaks for fast invalidation that existed prior to its
removal.
Paraphrashing the original changelog:
Zap at least 10 shadow pages before releasing mmu_lock to reduce the
overhead associated with re-acquiring the lock.
Note: "10" is an arbitrary number, speculated to be high enough so
that a vCPU isn't stuck zapping obsolete pages for an extended period,
but small enough so that other vCPUs aren't starved waiting for
mmu_lock.
This reverts commit 43d2b14b105fb00b8864c7b0ee7043cc1cc4a969.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
fbb158cb88