Merge pull request #1438 from arichardson/faster-tests-avoid-rand

Avoid millions of rand() calls() when running tests

2 files changed, 86 insertions, 0 deletions

diff --git a/test_utils/test_utils.c b/test_utils/test_utils.c
index 8ea3d3c4..db6c31b2 100644
--- a/test_utils/test_utils.c
+++ b/test_utils/test_utils.c
@@ -26,8 +26,11 @@
 
 #include "test_utils.h"
 
+#include <errno.h>
 #include <stdlib.h>
+#include <stdio.h>
 #include <string.h>
+#include <assert.h>
 
 /* Filter tests against a glob pattern. Returns non-zero if test matches
  * pattern, zero otherwise. A '^' at the beginning of the pattern negates
@@ -122,3 +125,81 @@ int get_test_set(int *test_set, int limit, const char *test,
 	}
 	return ((idx == 0)?-1:idx);
 }
+
+static inline uint64_t
+xorshift64(uint64_t *state)
+{
+	uint64_t x = *state;
+	x ^= x << 13;
+	x ^= x >> 7;
+	x ^= x << 17;
+	*state = x;
+	return (x);
+}
+
+/*
+ * Fill a buffer with reproducible pseudo-random data using a simple xorshift
+ * algorithm. Originally, most tests filled buffers with a loop that calls
+ * rand() once for each byte. However, this initialization can be extremely
+ * slow when running on emulated platforms such as QEMU where 16M calls to
+ * rand() take a long time: Before the test_write_format_7zip_large_copy test
+ * took ~22 seconds, whereas using a xorshift random number generator (that can
+ * be inlined) reduces it to ~17 seconds on QEMU RISC-V.
+ */
+void
+fill_with_pseudorandom_data_seed(uint64_t seed, void *buffer, size_t size)
+{
+	uint64_t *aligned_buffer;
+	size_t num_values;
+	size_t i;
+	size_t unaligned_suffix;
+	size_t unaligned_prefix = 0;
+	/*
+	 * To avoid unaligned stores we only fill the aligned part of the buffer
+	 * with pseudo-random data and fill the unaligned prefix with 0xab and
+	 * the suffix with 0xcd.
+	 */
+	if ((uintptr_t)buffer % sizeof(uint64_t)) {
+		unaligned_prefix =
+		    sizeof(uint64_t) - (uintptr_t)buffer % sizeof(uint64_t);
+		aligned_buffer =
+		    (uint64_t *)((char *)buffer + unaligned_prefix);
+		memset(buffer, 0xab, unaligned_prefix);
+	} else {
+		aligned_buffer = (uint64_t *)buffer;
+	}
+	assert((uintptr_t)aligned_buffer % sizeof(uint64_t) == 0);
+	num_values = (size - unaligned_prefix) / sizeof(uint64_t);
+	unaligned_suffix =
+	    size - unaligned_prefix - num_values * sizeof(uint64_t);
+	for (i = 0; i < num_values; i++) {
+		aligned_buffer[i] = xorshift64(&seed);
+	}
+	if (unaligned_suffix) {
+		memset((char *)buffer + size - unaligned_suffix, 0xcd,
+		    unaligned_suffix);
+	}
+}
+
+void
+fill_with_pseudorandom_data(void *buffer, size_t size)
+{
+	uint64_t seed;
+	const char* seed_str;
+	/*
+	 * Check if a seed has been specified in the environment, otherwise fall
+	 * back to using rand() as a seed.
+	 */
+	if ((seed_str = getenv("TEST_RANDOM_SEED")) != NULL) {
+		errno = 0;
+		seed = strtoull(seed_str, NULL, 10);
+		if (errno != 0) {
+			fprintf(stderr, "strtoull(%s) failed: %s", seed_str,
+			    strerror(errno));
+			seed = rand();
+		}
+	} else {
+		seed = rand();
+	}
+	fill_with_pseudorandom_data_seed(seed, buffer, size);
+}
diff --git a/test_utils/test_utils.h b/test_utils/test_utils.h
index 164c528f..3f61f6b2 100644
--- a/test_utils/test_utils.h
+++ b/test_utils/test_utils.h
@@ -27,6 +27,9 @@
 #ifndef TEST_UTILS_H
 #define TEST_UTILS_H
 
+#include <stddef.h>
+#include <stdint.h>
+
 struct test_list_t
 {
   void (*func)(void);
@@ -35,5 +38,7 @@ struct test_list_t
 };
 
 int get_test_set(int *, int, const char *, struct test_list_t *);
+void fill_with_pseudorandom_data(void* buffer, size_t size);
+void fill_with_pseudorandom_data_seed(uint64_t seed, void* buffer, size_t size);
 
 #endif /* TEST_UTILS_H */