[PATCH 2/3] KVM: selftests: Randomize which pages are written vs read

[Colton Lewis <coltonlewis@google.com>]

Randomize which pages are written vs read by using the random number
table for each page modulo 100. This changes how the -w argument
works. It is now a percentage from 0 to 100 inclusive that represents
what percentage of accesses are writes. It keeps the same default of
100 percent writes.

Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
 tools/testing/selftests/kvm/dirty_log_perf_test.c | 12 +++++++-----
 tools/testing/selftests/kvm/lib/perf_test_util.c  |  4 ++--
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/kvm/dirty_log_perf_test.c b/tools/testing/selftests/kvm/dirty_log_perf_test.c
index 80a1cbe7fbb0..dcc5d44fc757 100644
--- a/tools/testing/selftests/kvm/dirty_log_perf_test.c
+++ b/tools/testing/selftests/kvm/dirty_log_perf_test.c
@@ -381,8 +381,8 @@ static void help(char *name)
 	       "     (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");
+	       "     [0-100]%% of pages to write.\n"
+	       "     (default: 100 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");
@@ -399,7 +399,7 @@ 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,
+		.wr_fract = 100,
 		.partition_vcpu_memory_access = true,
 		.backing_src = DEFAULT_VM_MEM_SRC,
 		.slots = 1,
@@ -439,8 +439,10 @@ int main(int argc, char *argv[])
 			break;
 		case 'f':
 			p.wr_fract = atoi(optarg);
-			TEST_ASSERT(p.wr_fract >= 1,
-				    "Write fraction cannot be less than one");
+			TEST_ASSERT(p.wr_fract >= 0,
+				    "Write fraction cannot be less than 0");
+			TEST_ASSERT(p.wr_fract <= 100,
+				    "Write fraction cannot be greater than 100");
 			break;
 		case 'v':
 			nr_vcpus = atoi(optarg);
diff --git a/tools/testing/selftests/kvm/lib/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c
index b04e8d2c0f37..3c7b93349fef 100644
--- a/tools/testing/selftests/kvm/lib/perf_test_util.c
+++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
@@ -64,7 +64,7 @@ void perf_test_guest_code(uint32_t vcpu_idx)
 		for (i = 0; i < pages; i++) {
 			uint64_t addr = gva + (i * pta->guest_page_size);
 
-			if (i % pta->wr_fract == 0)
+			if (random_table[vcpu_idx][i] % 100 < pta->wr_fract)
 				*(uint64_t *)addr = 0x0123456789ABCDEF;
 			else
 				READ_ONCE(*(uint64_t *)addr);
@@ -168,7 +168,7 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int nr_vcpus,
 	pr_info("Testing guest mode: %s\n", vm_guest_mode_string(mode));
 
 	/* By default vCPUs will write to memory. */
-	pta->wr_fract = 1;
+	pta->wr_fract = 100;
 
 	/*
 	 * Snapshot the non-huge page size.  This is used by the guest code to
-- 
2.37.1.559.g78731f0fdb-goog