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 the current Unix timestamp.
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>
---
.../selftests/kvm/dirty_log_perf_test.c | 12 ++++++++++--
.../selftests/kvm/include/perf_test_util.h | 2 ++
.../testing/selftests/kvm/lib/perf_test_util.c | 18 +++++++++++++++++-
3 files changed, 29 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/kvm/dirty_log_perf_test.c b/tools/testing/selftests/kvm/dirty_log_perf_test.c
index d60a34cdfaee..2f91acd94130 100644
--- a/tools/testing/selftests/kvm/dirty_log_perf_test.c
+++ b/tools/testing/selftests/kvm/dirty_log_perf_test.c
@@ -126,6 +126,7 @@ 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)
@@ -220,6 +221,8 @@ static void run_test(enum vm_guest_mode mode, void *arg)
p->slots, p->backing_src,
p->partition_vcpu_memory_access);
+ 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);
@@ -337,7 +340,7 @@ 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",
@@ -362,6 +365,7 @@ 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");
@@ -378,6 +382,7 @@ int main(int argc, char *argv[])
.partition_vcpu_memory_access = true,
.backing_src = DEFAULT_VM_MEM_SRC,
.slots = 1,
+ .random_seed = time(NULL),
};
int opt;
@@ -388,7 +393,7 @@ int main(int argc, char *argv[])
guest_modes_append_default();
- while ((opt = getopt(argc, argv, "ghi:p:m:nb:f:v:os:x:")) != -1) {
+ while ((opt = getopt(argc, argv, "ghi:p:m:nb:f:v:or:s:x:")) != -1) {
switch (opt) {
case 'g':
dirty_log_manual_caps = 0;
@@ -421,6 +426,9 @@ 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 d822cb670f1c..f18530984b42 100644
--- a/tools/testing/selftests/kvm/include/perf_test_util.h
+++ b/tools/testing/selftests/kvm/include/perf_test_util.h
@@ -34,6 +34,7 @@ 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. */
@@ -51,6 +52,7 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int 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/lib/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c
index f989ff91f022..1292ed7d1193 100644
--- a/tools/testing/selftests/kvm/lib/perf_test_util.c
+++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
@@ -36,6 +36,13 @@ static void (*vcpu_thread_fn)(struct perf_test_vcpu_args *);
/* Set to true once all vCPU threads are up and running. */
static bool all_vcpu_threads_running;
+
+/* Park-Miller LCG using standard constants */
+static uint32_t perf_test_random(uint32_t seed)
+{
+ return (uint64_t)seed * 48271 % ((uint32_t)(1 << 31) - 1);
+}
+
/*
* Continuously write to the first 8 bytes of each page in the
* specified region.
@@ -47,6 +54,7 @@ void perf_test_guest_code(uint32_t vcpu_id)
uint64_t gva;
uint64_t pages;
int i;
+ uint32_t rand = pta->random_seed + vcpu_id;
/* Make sure vCPU args data structure is not corrupt. */
GUEST_ASSERT(vcpu_args->vcpu_id == vcpu_id);
@@ -56,6 +64,7 @@ void perf_test_guest_code(uint32_t vcpu_id)
while (true) {
for (i = 0; i < pages; i++) {
+ rand = perf_test_random(rand);
uint64_t addr = gva + (i * pta->guest_page_size);
if (i % pta->wr_fract == 0)
@@ -115,8 +124,9 @@ 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));
- /* By default vCPUs will write to memory. */
+ /* Set perf_test_args defaults. */
pta->wr_fract = 1;
+ pta->random_seed = time(NULL);
/*
* Snapshot the non-huge page size. This is used by the guest code to
@@ -224,6 +234,12 @@ 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);
+}
+
uint64_t __weak perf_test_nested_pages(int nr_vcpus)
{
return 0;
--
2.37.2.789.g6183377224-goog
