Implement random number generation for guest code to randomize parts
of the test, making it less predictable and a more accurate reflection
of reality.
Create a -r argument to specify a random seed. If no argument is
provided, the seed defaults to 0. The random seed is set with
perf_test_set_random_seed() and must be set before guest_code runs to
apply.
The random number generator chosen is the Park-Miller Linear
Congruential Generator, a fancy name for a basic and well-understood
random number generator entirely sufficient for this purpose. Each
vCPU calculates its own seed by adding its index to the seed provided.
Signed-off-by: Colton Lewis <coltonlewis@xxxxxxxxxx>
Reviewed-by: Ricardo Koller <ricarkol@xxxxxxxxxx>
Reviewed-by: David Matlack <dmatlack@xxxxxxxxxx>
---
.../testing/selftests/kvm/dirty_log_perf_test.c | 12 ++++++++++--
.../selftests/kvm/include/perf_test_util.h | 2 ++
tools/testing/selftests/kvm/include/test_util.h | 7 +++++++
.../testing/selftests/kvm/lib/perf_test_util.c | 7 +++++++
tools/testing/selftests/kvm/lib/test_util.c | 17 +++++++++++++++++
5 files changed, 43 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 f99e39a672d3..c97a5e455699 100644
--- a/tools/testing/selftests/kvm/dirty_log_perf_test.c
+++ b/tools/testing/selftests/kvm/dirty_log_perf_test.c
@@ -132,6 +132,7 @@ struct test_params {
bool partition_vcpu_memory_access;
enum vm_mem_backing_src_type backing_src;
int slots;
+ uint32_t random_seed;
};
static void toggle_dirty_logging(struct kvm_vm *vm, int slots, bool enable)
@@ -225,6 +226,9 @@ static void run_test(enum vm_guest_mode mode, void *arg)
p->slots, p->backing_src,
p->partition_vcpu_memory_access);
+ /* If no argument provided, random seed will be 1. */
+ pr_info("Random seed: %u\n", p->random_seed);
+ perf_test_set_random_seed(vm, p->random_seed ? p->random_seed : 1);
perf_test_set_wr_fract(vm, p->wr_fract);
guest_num_pages = (nr_vcpus * guest_percpu_mem_size) >> vm->page_shift;
@@ -352,7 +356,7 @@ static void help(char *name)
{
puts("");
printf("usage: %s [-h] [-i iterations] [-p offset] [-g] "
- "[-m mode] [-n] [-b vcpu bytes] [-v vcpus] [-o] [-s mem type]"
+ "[-m mode] [-n] [-b vcpu bytes] [-v vcpus] [-o] [-r random seed ] [-s mem type]"
"[-x memslots]\n", name);
puts("");
printf(" -i: specify iteration counts (default: %"PRIu64")\n",
@@ -380,6 +384,7 @@ static void help(char *name)
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");
+ printf(" -r: specify the starting random seed.\n");
backing_src_help("-s");
printf(" -x: Split the memory region into this number of memslots.\n"
" (default: 1)\n");
@@ -406,7 +411,7 @@ int main(int argc, char *argv[])
guest_modes_append_default();
- while ((opt = getopt(argc, argv, "eghi:p:m:nb:f:v:os:x:")) != -1) {
+ while ((opt = getopt(argc, argv, "eghi:p:m:nb:f:v:or:s:x:")) != -1) {
switch (opt) {
case 'e':
/* 'e' is for evil. */
@@ -442,6 +447,9 @@ int main(int argc, char *argv[])
case 'o':
p.partition_vcpu_memory_access = false;
break;
+ case 'r':
+ p.random_seed = atoi(optarg);
+ break;
case 's':
p.backing_src = parse_backing_src_type(optarg);
break;
diff --git a/tools/testing/selftests/kvm/include/perf_test_util.h b/tools/testing/selftests/kvm/include/perf_test_util.h
index eaa88df0555a..f1050fd42d10 100644
--- a/tools/testing/selftests/kvm/include/perf_test_util.h
+++ b/tools/testing/selftests/kvm/include/perf_test_util.h
@@ -35,6 +35,7 @@ struct perf_test_args {
uint64_t gpa;
uint64_t size;
uint64_t guest_page_size;
+ uint32_t random_seed;
int wr_fract;
/* Run vCPUs in L2 instead of L1, if the architecture supports it. */
@@ -52,6 +53,7 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int nr_vcpus,
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_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 *));
void perf_test_join_vcpu_threads(int vcpus);
diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index befc754ce9b3..9e4f36a1a8b0 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -152,4 +152,11 @@ static inline void *align_ptr_up(void *x, size_t size)
return (void *)align_up((unsigned long)x, size);
}
+struct guest_random_state {
+ uint32_t seed;
+};
+
+struct guest_random_state new_guest_random_state(uint32_t seed);
+uint32_t guest_random_u32(struct guest_random_state *state);
+
#endif /* SELFTEST_KVM_TEST_UTIL_H */
diff --git a/tools/testing/selftests/kvm/lib/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c
index 9618b37c66f7..5f0eebb626b5 100644
--- a/tools/testing/selftests/kvm/lib/perf_test_util.c
+++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
@@ -49,6 +49,7 @@ void perf_test_guest_code(uint32_t vcpu_idx)
uint64_t gva;
uint64_t pages;
int i;
+ struct guest_random_state rand_state = new_guest_random_state(pta->random_seed + vcpu_idx);
gva = vcpu_args->gva;
pages = vcpu_args->pages;
@@ -229,6 +230,12 @@ void perf_test_set_wr_fract(struct kvm_vm *vm, int wr_fract)
sync_global_to_guest(vm, perf_test_args);
}
+void perf_test_set_random_seed(struct kvm_vm *vm, uint32_t random_seed)
+{
+ perf_test_args.random_seed = random_seed;
+ sync_global_to_guest(vm, perf_test_args.random_seed);
+}
+
uint64_t __weak perf_test_nested_pages(int nr_vcpus)
{
return 0;
diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index 6d23878bbfe1..c4d2749fb2c3 100644
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -17,6 +17,23 @@
#include "test_util.h"
+/*
+ * Random number generator that is usable from guest code. This is the
+ * Park-Miller LCG using standard constants.
+ */
+
+struct guest_random_state new_guest_random_state(uint32_t seed)
+{
+ struct guest_random_state s = {.seed = seed};
+ return s;
+}
+
+uint32_t guest_random_u32(struct guest_random_state *state)
+{
+ state->seed = (uint64_t)state->seed * 48271 % ((uint32_t)(1 << 31) - 1);
+ return state->seed;
+}
+
/*
* Parses "[0-9]+[kmgt]?".
*/
--
2.38.0.413.g74048e4d9e-goog
