Hey Colton,
On Wed, Aug 17, 2022 at 09:41:46PM +0000, Colton Lewis wrote:
> Create the ability to randomize page access order with the -a
> argument, including the possibility that the same pages may be hit
> multiple times during an iteration or not at all.
>
> Signed-off-by: Colton Lewis <coltonlewis@xxxxxxxxxx>
> ---
> tools/testing/selftests/kvm/dirty_log_perf_test.c | 10 +++++++++-
> .../testing/selftests/kvm/include/perf_test_util.h | 2 ++
> tools/testing/selftests/kvm/lib/perf_test_util.c | 13 ++++++++++++-
> 3 files changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/dirty_log_perf_test.c b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> index 9226eeea79bc..af9754bda0a4 100644
> --- a/tools/testing/selftests/kvm/dirty_log_perf_test.c
> +++ b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> @@ -133,6 +133,7 @@ struct test_params {
> int slots;
> uint32_t write_percent;
> uint32_t random_seed;
> + bool random_access;
> };
>
> static void toggle_dirty_logging(struct kvm_vm *vm, int slots, bool enable)
> @@ -271,6 +272,9 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> pr_info("Enabling dirty logging time: %ld.%.9lds\n\n",
> ts_diff.tv_sec, ts_diff.tv_nsec);
>
> + /* Set random access here, after population phase. */
> + perf_test_set_random_access(vm, p->random_access);
> +
> while (iteration < p->iterations) {
> /*
> * Incrementing the iteration number will start the vCPUs
> @@ -353,10 +357,11 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> static void help(char *name)
> {
> puts("");
> - printf("usage: %s [-h] [-i iterations] [-p offset] [-g] "
> + printf("usage: %s [-h] [-a] [-i iterations] [-p offset] [-g] "
> "[-m mode] [-n] [-b vcpu bytes] [-v vcpus] [-o] [-r random seed ] [-s mem type]"
> "[-x memslots] [-w percentage]\n", name);
> puts("");
> + printf(" -a: access memory randomly rather than in order.\n");
> printf(" -i: specify iteration counts (default: %"PRIu64")\n",
> TEST_HOST_LOOP_N);
> printf(" -g: Do not enable KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2. This\n"
> @@ -413,6 +418,9 @@ int main(int argc, char *argv[])
>
> while ((opt = getopt(argc, argv, "eghi:p:m:nb:v:or:s:x:w:")) != -1) {
> switch (opt) {
> + case 'a':
> + p.random_access = true;
> + break;
> case 'e':
> /* 'e' is for evil. */
> run_vcpus_while_disabling_dirty_logging = true;
> diff --git a/tools/testing/selftests/kvm/include/perf_test_util.h b/tools/testing/selftests/kvm/include/perf_test_util.h
> index 8da4a839c585..237899f3f4fe 100644
> --- a/tools/testing/selftests/kvm/include/perf_test_util.h
> +++ b/tools/testing/selftests/kvm/include/perf_test_util.h
> @@ -41,6 +41,7 @@ struct perf_test_args {
>
> /* Run vCPUs in L2 instead of L1, if the architecture supports it. */
> bool nested;
> + bool random_access;
>
> struct perf_test_vcpu_args vcpu_args[KVM_MAX_VCPUS];
> };
> @@ -55,6 +56,7 @@ void perf_test_destroy_vm(struct kvm_vm *vm);
>
> void perf_test_set_write_percent(struct kvm_vm *vm, uint32_t write_percent);
> void perf_test_set_random_seed(struct kvm_vm *vm, uint32_t random_seed);
> +void perf_test_set_random_access(struct kvm_vm *vm, bool random_access);
>
> void perf_test_start_vcpu_threads(int vcpus, void (*vcpu_fn)(struct perf_test_vcpu_args *));
> void perf_test_join_vcpu_threads(int vcpus);
> diff --git a/tools/testing/selftests/kvm/lib/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c
> index 1a6b69713337..84e442a028c0 100644
> --- a/tools/testing/selftests/kvm/lib/perf_test_util.c
> +++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
> @@ -48,6 +48,7 @@ void perf_test_guest_code(uint32_t vcpu_idx)
> struct perf_test_vcpu_args *vcpu_args = &pta->vcpu_args[vcpu_idx];
> uint64_t gva;
> uint64_t pages;
> + uint64_t addr;
> uint32_t *rnd_arr = (uint32_t *)vcpu_args->random_array;
> int i;
>
> @@ -59,7 +60,11 @@ void perf_test_guest_code(uint32_t vcpu_idx)
>
> while (true) {
> for (i = 0; i < pages; i++) {
> - uint64_t addr = gva + (i * pta->guest_page_size);
> + if (pta->random_access)
> + addr = gva +
> + ((rnd_arr[i] % pages) * pta->guest_page_size);
> + else
> + addr = gva + (i * pta->guest_page_size);
>
> if (rnd_arr[i] % 100 < pta->write_percent)
> *(uint64_t *)addr = 0x0123456789ABCDEF;
I think addr and write_percent need two different random numbers.
Otherwise, you will end up with a situation where all addresses where
(rnd_arr[i] % 100 < pta->write_percent) will get a write (always).
Something like this:
012345678 <= address
wwwrrrwww
837561249 <= access order
I think the best way to fix this is to abstract the random number
reading into something like get_next_rand(), and use it twice per
iteration.
> @@ -271,6 +276,12 @@ void perf_test_set_random_seed(struct kvm_vm *vm, uint32_t random_seed)
> sync_global_to_guest(vm, perf_test_args);
> }
>
> +void perf_test_set_random_access(struct kvm_vm *vm, bool random_access)
> +{
> + perf_test_args.random_access = random_access;
> + sync_global_to_guest(vm, perf_test_args);
> +}
> +
> uint64_t __weak perf_test_nested_pages(int nr_vcpus)
> {
> return 0;
> --
> 2.37.1.595.g718a3a8f04-goog
>
Thanks,
Ricardo
