Re: [PATCH v2 3/3] KVM: selftests: Randomize page access order.

[David Matlack <dmatlack@google.com>]

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@google.com>
> ---
>  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);

Optional suggestion: We don't have any use-case for disabling random
access, so perhaps this would be simpler as:

  if (p->random_access)
          perf_test_enable_random_access(vm);

And then:

  void perf_test_enable_random_access(struct kvm_vm *vm)
  {
          perf_test_args.random_access = true;
          sync_global_to_guest(vm, perf_test_args);
  }

> +
>  	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;
> @@ -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
>