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kvm: x86: export maximum number of mmu_page_hash collisions 

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@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
David Matlack 2016-12-20 15:25:57 -08:00 committed by Radim Krčmář
parent 826da32140
commit f3414bc774
3 changed files with 20 additions and 8 deletions
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1
arch/x86/include/asm/kvm_host.h
View File

@ -821,6 +821,7 @@ struct kvm_vm_stat {
ulong mmu_unsync;
ulong remote_tlb_flush;
ulong lpages;
ulong max_mmu_page_hash_collisions;
};
struct kvm_vcpu_stat {

25
arch/x86/kvm/mmu.c
View File

@ -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 +2116,7 @@ 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;
LIST_HEAD(invalid_list);
role = vcpu->arch.mmu.base_role;
@ -2130,7 +2131,12 @@ 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;
@ -2153,7 +2159,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
__clear_sp_write_flooding_count(sp);
trace_kvm_mmu_get_page(sp, false);
return sp;
goto out;
}
++vcpu->kvm->stat.mmu_cache_miss;
@ -2183,6 +2189,9 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
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;
return sp;
}

2
arch/x86/kvm/x86.c
View File

@ -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 }
};