Report the maximum number of mmu_page_hash collisions as a per-VM stat.
This will make it easy to identify problems with the mmu_page_hash in
the future.
Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>
Change-Id: I096fc6d5a3589e7f19fcc9c2a1b8a37c7368ba17
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/mmu.c | 31 +++++++++++++++++++++----------
arch/x86/kvm/x86.c | 2 ++
3 files changed, 24 insertions(+), 10 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 2e25038..8ba0d64 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -815,6 +815,7 @@ struct kvm_vm_stat {
ulong mmu_unsync;
ulong remote_tlb_flush;
ulong lpages;
+ ulong max_mmu_page_hash_collisions;
};
struct kvm_vcpu_stat {
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 7012de4..58995fd9 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1904,17 +1904,17 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,
* since it has been deleted from active_mmu_pages but still can be found
* at hast list.
*
- * for_each_gfn_valid_sp() has skipped that kind of pages.
+ * for_each_valid_sp() has skipped that kind of pages.
*/
-#define for_each_gfn_valid_sp(_kvm, _sp, _gfn) \
+#define for_each_valid_sp(_kvm, _sp, _gfn) \
hlist_for_each_entry(_sp, \
&(_kvm)->arch.mmu_page_hash[kvm_page_table_hashfn(_gfn)], hash_link) \
- if ((_sp)->gfn != (_gfn) || is_obsolete_sp((_kvm), (_sp)) \
- || (_sp)->role.invalid) {} else
+ if (is_obsolete_sp((_kvm), (_sp)) || (_sp)->role.invalid) { \
+ } else
#define for_each_gfn_indirect_valid_sp(_kvm, _sp, _gfn) \
- for_each_gfn_valid_sp(_kvm, _sp, _gfn) \
- if ((_sp)->role.direct) {} else
+ for_each_valid_sp(_kvm, _sp, _gfn) \
+ if ((_sp)->gfn != (_gfn) || (_sp)->role.direct) {} else
/* @sp->gfn should be write-protected at the call site */
static bool __kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
@@ -2116,6 +2116,8 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
struct kvm_mmu_page *sp;
bool need_sync = false;
bool flush = false;
+ int collisions = 0;
+ bool created = true;
LIST_HEAD(invalid_list);
role = vcpu->arch.mmu.base_role;
@@ -2130,7 +2132,12 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
quadrant &= (1 << ((PT32_PT_BITS - PT64_PT_BITS) * level)) - 1;
role.quadrant = quadrant;
}
- for_each_gfn_valid_sp(vcpu->kvm, sp, gfn) {
+ for_each_valid_sp(vcpu->kvm, sp, gfn) {
+ if (sp->gfn != gfn) {
+ collisions++;
+ continue;
+ }
+
if (!need_sync && sp->unsync)
need_sync = true;
@@ -2152,8 +2159,8 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);
__clear_sp_write_flooding_count(sp);
- trace_kvm_mmu_get_page(sp, false);
- return sp;
+ created = false;
+ goto out;
}
++vcpu->kvm->stat.mmu_cache_miss;
@@ -2164,6 +2171,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
sp->role = role;
hlist_add_head(&sp->hash_link,
&vcpu->kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)]);
+
if (!direct) {
/*
* we should do write protection before syncing pages
@@ -2180,9 +2188,12 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
}
sp->mmu_valid_gen = vcpu->kvm->arch.mmu_valid_gen;
clear_page(sp->spt);
- trace_kvm_mmu_get_page(sp, true);
kvm_mmu_flush_or_zap(vcpu, &invalid_list, false, flush);
+out:
+ if (collisions > vcpu->kvm->stat.max_mmu_page_hash_collisions)
+ vcpu->kvm->stat.max_mmu_page_hash_collisions = collisions;
+ trace_kvm_mmu_get_page(sp, created);
return sp;
}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8f86c0c..ee4c35e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -190,6 +190,8 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
{ "mmu_unsync", VM_STAT(mmu_unsync) },
{ "remote_tlb_flush", VM_STAT(remote_tlb_flush) },
{ "largepages", VM_STAT(lpages) },
+ { "max_mmu_page_hash_collisions",
+ VM_STAT(max_mmu_page_hash_collisions) },
{ NULL }
};
--
2.8.0.rc3.226.g39d4020
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
