[PATCH v4 12/16] KVM: selftests: Report per-vcpu demand paging rate from demand paging test

[Anish Moorthy <amoorthy@google.com>]

Using the overall demand paging rate to measure performance can be
slightly misleading when vCPU accesses are not overlapped. Adding more
vCPUs will (usually) increase the overall demand paging rate even
if performance remains constant or even degrades on a per-vcpu basis. As
such, it makes sense to report both the total and per-vcpu paging rates.

Signed-off-by: Anish Moorthy <amoorthy@google.com>
---
 tools/testing/selftests/kvm/demand_paging_test.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
index 9c18686b4f63..5e8bda388814 100644
--- a/tools/testing/selftests/kvm/demand_paging_test.c
+++ b/tools/testing/selftests/kvm/demand_paging_test.c
@@ -135,6 +135,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
 	struct timespec ts_diff;
 	struct kvm_vm *vm;
 	int i;
+	double vcpu_paging_rate;
 
 	vm = memstress_create_vm(mode, nr_vcpus, guest_percpu_mem_size, 1,
 				 p->src_type, p->partition_vcpu_memory_access);
@@ -191,11 +192,17 @@ static void run_test(enum vm_guest_mode mode, void *arg)
 			uffd_stop_demand_paging(uffd_descs[i]);
 	}
 
-	pr_info("Total guest execution time: %ld.%.9lds\n",
+	pr_info("Total guest execution time:\t%ld.%.9lds\n",
 		ts_diff.tv_sec, ts_diff.tv_nsec);
-	pr_info("Overall demand paging rate: %f pgs/sec\n",
-		memstress_args.vcpu_args[0].pages * nr_vcpus /
-		((double)ts_diff.tv_sec + (double)ts_diff.tv_nsec / NSEC_PER_SEC));
+
+	vcpu_paging_rate =
+		memstress_args.vcpu_args[0].pages
+		/ ((double)ts_diff.tv_sec
+			+ (double)ts_diff.tv_nsec / NSEC_PER_SEC);
+	pr_info("Per-vcpu demand paging rate:\t%f pgs/sec/vcpu\n",
+		vcpu_paging_rate);
+	pr_info("Overall demand paging rate:\t%f pgs/sec\n",
+		vcpu_paging_rate * nr_vcpus);
 
 	memstress_destroy_vm(vm);
 
-- 
2.41.0.rc0.172.g3f132b7071-goog