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-rw-r--r--tools/perf/bench/find-bit-bench.c135
1 files changed, 135 insertions, 0 deletions
diff --git a/tools/perf/bench/find-bit-bench.c b/tools/perf/bench/find-bit-bench.c
new file mode 100644
index 000000000..73b5bcc59
--- /dev/null
+++ b/tools/perf/bench/find-bit-bench.c
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Benchmark find_next_bit and related bit operations.
+ *
+ * Copyright 2020 Google LLC.
+ */
+#include <stdlib.h>
+#include "bench.h"
+#include "../util/stat.h"
+#include <linux/bitmap.h>
+#include <linux/bitops.h>
+#include <linux/time64.h>
+#include <subcmd/parse-options.h>
+
+static unsigned int outer_iterations = 5;
+static unsigned int inner_iterations = 100000;
+
+static const struct option options[] = {
+ OPT_UINTEGER('i', "outer-iterations", &outer_iterations,
+ "Number of outer iterations used"),
+ OPT_UINTEGER('j', "inner-iterations", &inner_iterations,
+ "Number of inner iterations used"),
+ OPT_END()
+};
+
+static const char *const bench_usage[] = {
+ "perf bench mem find_bit <options>",
+ NULL
+};
+
+static unsigned int accumulator;
+static unsigned int use_of_val;
+
+static noinline void workload(int val)
+{
+ use_of_val += val;
+ accumulator++;
+}
+
+#if (defined(__i386__) || defined(__x86_64__)) && defined(__GCC_ASM_FLAG_OUTPUTS__)
+static bool asm_test_bit(long nr, const unsigned long *addr)
+{
+ bool oldbit;
+
+ asm volatile("bt %2,%1"
+ : "=@ccc" (oldbit)
+ : "m" (*(unsigned long *)addr), "Ir" (nr) : "memory");
+
+ return oldbit;
+}
+#else
+#define asm_test_bit test_bit
+#endif
+
+static int do_for_each_set_bit(unsigned int num_bits)
+{
+ unsigned long *to_test = bitmap_alloc(num_bits);
+ struct timeval start, end, diff;
+ u64 runtime_us;
+ struct stats fb_time_stats, tb_time_stats;
+ double time_average, time_stddev;
+ unsigned int bit, i, j;
+ unsigned int set_bits, skip;
+ unsigned int old;
+
+ init_stats(&fb_time_stats);
+ init_stats(&tb_time_stats);
+
+ for (set_bits = 1; set_bits <= num_bits; set_bits <<= 1) {
+ bitmap_zero(to_test, num_bits);
+ skip = num_bits / set_bits;
+ for (i = 0; i < num_bits; i += skip)
+ set_bit(i, to_test);
+
+ for (i = 0; i < outer_iterations; i++) {
+ old = accumulator;
+ gettimeofday(&start, NULL);
+ for (j = 0; j < inner_iterations; j++) {
+ for_each_set_bit(bit, to_test, num_bits)
+ workload(bit);
+ }
+ gettimeofday(&end, NULL);
+ assert(old + (inner_iterations * set_bits) == accumulator);
+ timersub(&end, &start, &diff);
+ runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
+ update_stats(&fb_time_stats, runtime_us);
+
+ old = accumulator;
+ gettimeofday(&start, NULL);
+ for (j = 0; j < inner_iterations; j++) {
+ for (bit = 0; bit < num_bits; bit++) {
+ if (asm_test_bit(bit, to_test))
+ workload(bit);
+ }
+ }
+ gettimeofday(&end, NULL);
+ assert(old + (inner_iterations * set_bits) == accumulator);
+ timersub(&end, &start, &diff);
+ runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
+ update_stats(&tb_time_stats, runtime_us);
+ }
+
+ printf("%d operations %d bits set of %d bits\n",
+ inner_iterations, set_bits, num_bits);
+ time_average = avg_stats(&fb_time_stats);
+ time_stddev = stddev_stats(&fb_time_stats);
+ printf(" Average for_each_set_bit took: %.3f usec (+- %.3f usec)\n",
+ time_average, time_stddev);
+ time_average = avg_stats(&tb_time_stats);
+ time_stddev = stddev_stats(&tb_time_stats);
+ printf(" Average test_bit loop took: %.3f usec (+- %.3f usec)\n",
+ time_average, time_stddev);
+
+ if (use_of_val == accumulator) /* Try to avoid compiler tricks. */
+ printf("\n");
+ }
+ bitmap_free(to_test);
+ return 0;
+}
+
+int bench_mem_find_bit(int argc, const char **argv)
+{
+ int err = 0, i;
+
+ argc = parse_options(argc, argv, options, bench_usage, 0);
+ if (argc) {
+ usage_with_options(bench_usage, options);
+ exit(EXIT_FAILURE);
+ }
+
+ for (i = 1; i <= 2048; i <<= 1)
+ do_for_each_set_bit(i);
+
+ return err;
+}