Use the recently introduced kvm_mmu_zap_oldest_mmu_pages() to batch zap
MMU pages when shrinking a slab. This fixes a long standing issue where
KVM's shrinker implementation is completely ineffective due to zapping
only a single page. E.g. without batch zapping, forcing a scan via
drop_caches basically has no impact on a VM with ~2k shadow pages. With
batch zapping, the number of shadow pages can be reduced to a few
hundred pages in one or two runs of drop_caches.
Note, if the default batch size (currently 128) is problematic, e.g.
zapping 128 pages holds mmu_lock for too long, KVM can bound the batch
size by setting @batch in mmu_shrinker.
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
arch/x86/kvm/mmu/mmu.c | 17 +----------------
1 file changed, 1 insertion(+), 16 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 8c85a3a178f4..4d40b21a67bd 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -2825,19 +2825,6 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,
}
}
-static bool prepare_zap_oldest_mmu_page(struct kvm *kvm,
- struct list_head *invalid_list)
-{
- struct kvm_mmu_page *sp;
-
- if (list_empty(&kvm->arch.active_mmu_pages))
- return false;
-
- sp = list_last_entry(&kvm->arch.active_mmu_pages,
- struct kvm_mmu_page, link);
- return kvm_mmu_prepare_zap_page(kvm, sp, invalid_list);
-}
-
static unsigned long kvm_mmu_zap_oldest_mmu_pages(struct kvm *kvm,
unsigned long nr_to_zap)
{
@@ -6125,9 +6112,7 @@ mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
goto unlock;
}
- if (prepare_zap_oldest_mmu_page(kvm, &invalid_list))
- freed++;
- kvm_mmu_commit_zap_page(kvm, &invalid_list);
+ freed = kvm_mmu_zap_oldest_mmu_pages(kvm, sc->nr_to_scan);
unlock:
spin_unlock(&kvm->mmu_lock);
--
2.26.0
