On Fri, Sep 09, 2022 at 12:42:59PM +0000, Colton Lewis wrote:
> Randomize which pages are written vs read using the random number
> generator.
>
> Change the variable wr_fract and associated function calls to
> write_percent that now operates as a percentage from 0 to 100 where X
> means each page has an X% chance of being written. Change the -f
> argument to -w to reflect the new variable semantics. Keep the same
> default of 100% writes.
>
> Population always uses 100% writes.
>
> Signed-off-by: Colton Lewis <coltonlewis@xxxxxxxxxx>
> ---
> .../selftests/kvm/access_tracking_perf_test.c | 2 +-
> .../selftests/kvm/dirty_log_perf_test.c | 30 +++++++++++--------
> .../selftests/kvm/include/perf_test_util.h | 4 +--
> .../selftests/kvm/lib/perf_test_util.c | 10 +++----
> 4 files changed, 25 insertions(+), 21 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/access_tracking_perf_test.c b/tools/testing/selftests/kvm/access_tracking_perf_test.c
> index d8909032317a..d86046ef3a0b 100644
> --- a/tools/testing/selftests/kvm/access_tracking_perf_test.c
> +++ b/tools/testing/selftests/kvm/access_tracking_perf_test.c
> @@ -274,7 +274,7 @@ static void run_iteration(struct kvm_vm *vm, int vcpus, const char *description)
> static void access_memory(struct kvm_vm *vm, int vcpus, enum access_type access,
> const char *description)
> {
> - perf_test_set_wr_fract(vm, (access == ACCESS_READ) ? INT_MAX : 1);
> + perf_test_set_write_percent(vm, (access == ACCESS_READ) ? 0 : 100);
> iteration_work = ITERATION_ACCESS_MEMORY;
> run_iteration(vm, vcpus, description);
> }
> diff --git a/tools/testing/selftests/kvm/dirty_log_perf_test.c b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> index 2f91acd94130..c2ad299b3760 100644
> --- a/tools/testing/selftests/kvm/dirty_log_perf_test.c
> +++ b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> @@ -122,10 +122,10 @@ static void vcpu_worker(struct perf_test_vcpu_args *vcpu_args)
> struct test_params {
> unsigned long iterations;
> uint64_t phys_offset;
> - int wr_fract;
> bool partition_vcpu_memory_access;
> enum vm_mem_backing_src_type backing_src;
> int slots;
> + uint32_t write_percent;
> uint32_t random_seed;
> };
>
> @@ -223,7 +223,6 @@ static void run_test(enum vm_guest_mode mode, void *arg)
>
> pr_info("Random seed: %u\n", p->random_seed);
> perf_test_set_random_seed(vm, p->random_seed);
> - perf_test_set_wr_fract(vm, p->wr_fract);
>
> guest_num_pages = (nr_vcpus * guest_percpu_mem_size) >> vm_get_page_shift(vm);
> guest_num_pages = vm_adjust_num_guest_pages(mode, guest_num_pages);
> @@ -248,6 +247,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++)
> vcpu_last_completed_iteration[vcpu_id] = -1;
>
> + perf_test_set_write_percent(vm, 100);
This is a very important line of code and it's not very clear why it's
here to a random reader. Please a comment here so someone doesn't have
to go through the same confusion/debugging we went through to figure out
why this is necessary. e.g.
/*
* Use 100% writes during the population phase to ensure all
* memory is actually populated and not just mapped to the zero
* page. The prevents expensive copy-on-write faults from
* occurring during the dirty memory iterations below, which
* would pollute the performance results.
*/
perf_test_set_write_percent(vm, 100);
Aside from that,
Reviewed-by: David Matlack <dmatlack@xxxxxxxxxx>
> perf_test_start_vcpu_threads(nr_vcpus, vcpu_worker);
>
> /* Allow the vCPUs to populate memory */
> @@ -269,6 +269,8 @@ 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);
>
> + perf_test_set_write_percent(vm, p->write_percent);
> +
> while (iteration < p->iterations) {
> /*
> * Incrementing the iteration number will start the vCPUs
> @@ -341,7 +343,7 @@ static void help(char *name)
> puts("");
> printf("usage: %s [-h] [-i iterations] [-p offset] [-g] "
> "[-m mode] [-n] [-b vcpu bytes] [-v vcpus] [-o] [-r random seed ] [-s mem type]"
> - "[-x memslots]\n", name);
> + "[-x memslots] [-w percentage]\n", name);
> puts("");
> printf(" -i: specify iteration counts (default: %"PRIu64")\n",
> TEST_HOST_LOOP_N);
> @@ -358,10 +360,6 @@ static void help(char *name)
> printf(" -b: specify the size of the memory region which should be\n"
> " dirtied by each vCPU. e.g. 10M or 3G.\n"
> " (default: 1G)\n");
> - printf(" -f: specify the fraction of pages which should be written to\n"
> - " as opposed to simply read, in the form\n"
> - " 1/<fraction of pages to write>.\n"
> - " (default: 1 i.e. all pages are written to.)\n");
> printf(" -v: specify the number of vCPUs to run.\n");
> printf(" -o: Overlap guest memory accesses instead of partitioning\n"
> " them into a separate region of memory for each vCPU.\n");
> @@ -369,6 +367,11 @@ static void help(char *name)
> backing_src_help("-s");
> printf(" -x: Split the memory region into this number of memslots.\n"
> " (default: 1)\n");
> + printf(" -w: specify the percentage of pages which should be written to\n"
> + " as an integer from 0-100 inclusive. This is probabalistic,\n"
> + " so -w X means each page has an X%% chance of writing\n"
> + " and a (100-X)%% chance of reading.\n"
> + " (default: 100 i.e. all pages are written to.)\n");
> puts("");
> exit(0);
> }
> @@ -378,10 +381,10 @@ int main(int argc, char *argv[])
> int max_vcpus = kvm_check_cap(KVM_CAP_MAX_VCPUS);
> struct test_params p = {
> .iterations = TEST_HOST_LOOP_N,
> - .wr_fract = 1,
> .partition_vcpu_memory_access = true,
> .backing_src = DEFAULT_VM_MEM_SRC,
> .slots = 1,
> + .write_percent = 100,
> .random_seed = time(NULL),
> };
> int opt;
> @@ -393,7 +396,7 @@ int main(int argc, char *argv[])
>
> guest_modes_append_default();
>
> - while ((opt = getopt(argc, argv, "ghi:p:m:nb:f:v:or:s:x:")) != -1) {
> + while ((opt = getopt(argc, argv, "ghi:p:m:nb:v:or:s:x:w:")) != -1) {
> switch (opt) {
> case 'g':
> dirty_log_manual_caps = 0;
> @@ -413,10 +416,11 @@ int main(int argc, char *argv[])
> case 'b':
> guest_percpu_mem_size = parse_size(optarg);
> break;
> - case 'f':
> - p.wr_fract = atoi(optarg);
> - TEST_ASSERT(p.wr_fract >= 1,
> - "Write fraction cannot be less than one");
> + case 'w':
> + p.write_percent = atoi(optarg);
> + TEST_ASSERT(p.write_percent >= 0
> + && p.write_percent <= 100,
> + "Write percentage must be between 0 and 100");
> break;
> case 'v':
> nr_vcpus = atoi(optarg);
> diff --git a/tools/testing/selftests/kvm/include/perf_test_util.h b/tools/testing/selftests/kvm/include/perf_test_util.h
> index f18530984b42..f93f2ea7c6a3 100644
> --- a/tools/testing/selftests/kvm/include/perf_test_util.h
> +++ b/tools/testing/selftests/kvm/include/perf_test_util.h
> @@ -35,7 +35,7 @@ struct perf_test_args {
> uint64_t size;
> uint64_t guest_page_size;
> uint32_t random_seed;
> - int wr_fract;
> + uint32_t write_percent;
>
> /* Run vCPUs in L2 instead of L1, if the architecture supports it. */
> bool nested;
> @@ -51,7 +51,7 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int vcpus,
> bool partition_vcpu_memory_access);
> void perf_test_destroy_vm(struct kvm_vm *vm);
>
> -void perf_test_set_wr_fract(struct kvm_vm *vm, int wr_fract);
> +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_start_vcpu_threads(int vcpus, void (*vcpu_fn)(struct perf_test_vcpu_args *));
> diff --git a/tools/testing/selftests/kvm/lib/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c
> index 4d9c7d7693d9..12a3597be1f9 100644
> --- a/tools/testing/selftests/kvm/lib/perf_test_util.c
> +++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
> @@ -60,7 +60,7 @@ void perf_test_guest_code(uint32_t vcpu_id)
> uint64_t addr = gva + (i * pta->guest_page_size);
> guest_random(&rand);
>
> - if (i % pta->wr_fract == 0)
> + if (rand % 100 < pta->write_percent)
> *(uint64_t *)addr = 0x0123456789ABCDEF;
> else
> READ_ONCE(*(uint64_t *)addr);
> @@ -118,7 +118,7 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int vcpus,
> pr_info("Testing guest mode: %s\n", vm_guest_mode_string(mode));
>
> /* Set perf_test_args defaults. */
> - pta->wr_fract = 1;
> + pta->write_percent = 100;
> pta->random_seed = time(NULL);
>
> /*
> @@ -221,10 +221,10 @@ void perf_test_destroy_vm(struct kvm_vm *vm)
> kvm_vm_free(vm);
> }
>
> -void perf_test_set_wr_fract(struct kvm_vm *vm, int wr_fract)
> +void perf_test_set_write_percent(struct kvm_vm *vm, uint32_t write_percent)
> {
> - perf_test_args.wr_fract = wr_fract;
> - sync_global_to_guest(vm, perf_test_args);
> + perf_test_args.write_percent = write_percent;
> + sync_global_to_guest(vm, perf_test_args.write_percent);
> }
>
> void perf_test_set_random_seed(struct kvm_vm *vm, uint32_t random_seed)
> --
> 2.37.2.789.g6183377224-goog
>
