[PATCH v7 11/11] KVM: selftests: Cache binary stats metadata for duration of test

Ben Gardon
2022-05-03T18:31:29Z

In order to improve performance across multiple reads of VM stats, cache
the stats metadata in the VM struct.

Signed-off-by: Ben Gardon <bgardon@google.com>
---
tools/testing/selftests/kvm/lib/kvm_util.c | 31 ++++++++++---------
.../selftests/kvm/lib/kvm_util_internal.h | 5 +++
2 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 0ec7efc2900d..4bb012efcc88 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -736,6 +736,12 @@ void kvm_vm_free(struct kvm_vm *vmp)
if (vmp == NULL)
return;

+ /* Free cached stats metadata and close FD */
+ if (vmp->stats_fd) {
+ free(vmp->stats_desc);
+ close(vmp->stats_fd);
+ }
+
/* Free userspace_mem_regions. */
hash_for_each_safe(vmp->regions.slot_hash, ctr, node, region, slot_node)
__vm_mem_region_delete(vmp, region, false);
@@ -2703,37 +2709,32 @@ int read_stat_data(int stats_fd, struct kvm_stats_header *header,
static int __vm_get_stat(struct kvm_vm *vm, const char *stat_name,
uint64_t *data, ssize_t max_elements)
{
- struct kvm_stats_desc *stats_desc;
- struct kvm_stats_header header;
struct kvm_stats_desc *desc;
size_t size_desc;
- int stats_fd;
int ret = -EINVAL;
int i;

- stats_fd = vm_get_stats_fd(vm);
-
- read_stats_header(stats_fd, &header);
-
- stats_desc = read_stats_desc(stats_fd, &header);
+ if (!vm->stats_fd) {
+ vm->stats_fd = vm_get_stats_fd(vm);
+ read_stats_header(vm->stats_fd, &vm->stats_header);
+ vm->stats_desc = read_stats_desc(vm->stats_fd, &vm->stats_header);
+ }

- size_desc = sizeof(struct kvm_stats_desc) + header.name_size;
+ size_desc = sizeof(struct kvm_stats_desc) + vm->stats_header.name_size;

/* Read kvm stats data one by one */
- for (i = 0; i < header.num_desc; ++i) {
- desc = (void *)stats_desc + (i * size_desc);
+ for (i = 0; i < vm->stats_header.num_desc; ++i) {
+ desc = (void *)vm->stats_desc + (i * size_desc);

if (strcmp(desc->name, stat_name))
continue;

- ret = read_stat_data(stats_fd, &header, desc, data,
- max_elements);
+ ret = read_stat_data(vm->stats_fd, &vm->stats_header, desc,
+ data, max_elements);

break;
}

- free(stats_desc);
- close(stats_fd);
return ret;
}

diff --git a/tools/testing/selftests/kvm/lib/kvm_util_internal.h b/tools/testing/selftests/kvm/lib/kvm_util_internal.h
index a03febc24ba6..e753edd7b8d3 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util_internal.h
+++ b/tools/testing/selftests/kvm/lib/kvm_util_internal.h
@@ -67,6 +67,11 @@ struct kvm_vm {
vm_vaddr_t idt;
vm_vaddr_t handlers;
uint32_t dirty_ring_size;
+
+ /* Cache of information for binary stats interface */
+ int stats_fd;
+ struct kvm_stats_header stats_header;
+ struct kvm_stats_desc *stats_desc;
};

struct vcpu *vcpu_find(struct kvm_vm *vm, uint32_t vcpuid);
--
2.36.0.464.gb9c8b46e94-goog