The mmu_shrink() is heavy by itself by iterating all kvms and holding
the kvm_lock. spotted the code w/ Rik during LSF, and it turns out we
don't need to call the shrinker if nothing to shrink.
Signed-off-by: Ying Han <yinghan@xxxxxxxxxx>
---
arch/x86/kvm/mmu.c | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 4cb1642..7025736 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -188,6 +188,11 @@ static u64 __read_mostly shadow_mmio_mask;
static void mmu_spte_set(u64 *sptep, u64 spte);
+static inline int get_kvm_total_used_mmu_pages()
+{
+ return percpu_counter_read_positive(&kvm_total_used_mmu_pages);
+}
+
void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask)
{
shadow_mmio_mask = mmio_mask;
@@ -3900,6 +3905,9 @@ static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)
if (nr_to_scan == 0)
goto out;
+ if (!get_kvm_total_used_mmu_pages())
+ return 0;
+
raw_spin_lock(&kvm_lock);
list_for_each_entry(kvm, &vm_list, vm_list) {
@@ -3926,7 +3934,7 @@ static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)
raw_spin_unlock(&kvm_lock);
out:
- return percpu_counter_read_positive(&kvm_total_used_mmu_pages);
+ return get_kvm_total_used_mmu_pages();
}
static struct shrinker mmu_shrinker = {
--
1.7.7.3
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