On Thu, Feb 15, 2024, Anish Moorthy wrote:
> 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@xxxxxxxxxx>
> ---
> 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 09c116a82a84..6dc823fa933a 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);
*sigh*
For the umpteenth time, please follow kernel coding style. Either
vcpu_paging_rate = memstress_args.vcpu_args[0].pages /
((double)ts_diff.tv_sec + (double)ts_diff.tv_nsec / NSEC_PER_SEC);
or
vcpu_paging_rate = memstress_args.vcpu_args[0].pages /
((double)ts_diff.tv_sec +
(double)ts_diff.tv_nsec / NSEC_PER_SEC);
I don't have a strong preference, so I'll go with the first one when applying.
