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 <[email protected]> --- 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
