KVM: selftests: randomize page access order

Create the ability to randomize page access order with the -a
argument. This includes the possibility that the same pages may be hit
multiple times during an iteration or not at all.

Population has random access as false to ensure all pages will be
touched by population and avoid page faults in late dirty memory that
would pollute the test results.

Signed-off-by: Colton Lewis <coltonlewis@google.com>
Reviewed-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20221107182208.479157-5-coltonlewis@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/tools/testing/selftests/kvm/dirty_log_perf_test.c b/tools/testing/selftests/kvm/dirty_log_perf_test.c
index e9ce50fe7295c14e4b861a714b8e6a1b4ee0ee53..47cbda3580fd6d161d519682372e917fe299de01 100644 (file)
--- 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)
@@ -259,6 +260,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
         * would pollute the performance results.
         */
        perf_test_set_write_percent(vm, 100);
+       perf_test_set_random_access(vm, false);
        perf_test_start_vcpu_threads(nr_vcpus, vcpu_worker);
 
        /* Allow the vCPUs to populate memory */
@@ -281,6 +283,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
                ts_diff.tv_sec, ts_diff.tv_nsec);
 
        perf_test_set_write_percent(vm, p->write_percent);
+       perf_test_set_random_access(vm, p->random_access);
 
        while (iteration < p->iterations) {
                /*
@@ -364,10 +367,11 @@ 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] [-c physical cpus to run test on]\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"
@@ -434,8 +438,11 @@ int main(int argc, char *argv[])
 
        guest_modes_append_default();
 
-       while ((opt = getopt(argc, argv, "b:c:eghi:m:nop:r:s:v:x:w:")) != -1) {
+       while ((opt = getopt(argc, argv, "ab:c:eghi:m:nop:r:s:v:x:w:")) != -1) {
                switch (opt) {
+               case 'a':
+                       p.random_access = true;
+                       break;
                case 'b':
                        guest_percpu_mem_size = parse_size(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 6470ca0fec4c05cccc08e93b0b449b2aed41329f..75ca679059dc26e479040f56a7e70cac83a30b20 100644 (file)
--- a/tools/testing/selftests/kvm/include/perf_test_util.h
+++ b/tools/testing/selftests/kvm/include/perf_test_util.h
@@ -40,6 +40,8 @@ struct perf_test_args {
 
        /* Run vCPUs in L2 instead of L1, if the architecture supports it. */
        bool nested;
+       /* Randomize which pages are accessed by the guest. */
+       bool random_access;
        /* True if all vCPUs are pinned to pCPUs */
        bool pin_vcpus;
        /* The vCPU=>pCPU pinning map. Only valid if pin_vcpus is true. */
@@ -58,6 +60,7 @@ 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 15000f71cdeea14506c42eddc4681247f88110ec..3a9a3ea01a9735ccf7b0252abd31b7a1302e557f 100644 (file)
--- a/tools/testing/selftests/kvm/lib/perf_test_util.c
+++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
@@ -51,6 +51,8 @@ void perf_test_guest_code(uint32_t vcpu_idx)
        struct guest_random_state rand_state;
        uint64_t gva;
        uint64_t pages;
+       uint64_t addr;
+       uint64_t page;
        int i;
 
        rand_state = new_guest_random_state(pta->random_seed + vcpu_idx);
@@ -63,7 +65,12 @@ 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)
+                               page = guest_random_u32(&rand_state) % pages;
+                       else
+                               page = i;
+
+                       addr = gva + (page * pta->guest_page_size);
 
                        if (guest_random_u32(&rand_state) % 100 < pta->write_percent)
                                *(uint64_t *)addr = 0x0123456789ABCDEF;
@@ -240,6 +247,12 @@ void perf_test_set_random_seed(struct kvm_vm *vm, uint32_t random_seed)
        sync_global_to_guest(vm, perf_test_args.random_seed);
 }
 
+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.random_access);
+}
+
 uint64_t __weak perf_test_nested_pages(int nr_vcpus)
 {
        return 0;