KVM: selftests: Report per-vcpu demand paging rate from demand paging test

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>
Link: https://lore.kernel.org/r/20240215235405.368539-11-amoorthy@google.com
[sean: fix formatting]
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
index bf3609f718544fb2b5d6c116d8eec4b28c29ab98..ddacbc6fd1ed5e7cdad461e379ce8e8ea5d1e799 100644 (file)
--- a/tools/testing/selftests/kvm/demand_paging_test.c
+++ b/tools/testing/selftests/kvm/demand_paging_test.c
@@ -133,6 +133,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
        struct uffd_desc **uffd_descs = NULL;
        struct timespec start;
        struct timespec ts_diff;
+       double vcpu_paging_rate;
        struct kvm_vm *vm;
        int i;
 
@@ -191,11 +192,15 @@ 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);