From 070e3edceaa023109bfa7a1c5c259342e0b6b625 Mon Sep 17 00:00:00 2001 From: "Emilio G. Cota" Date: Mon, 27 Jun 2016 15:02:05 -0400 Subject: [PATCH] tests: add atomic_add-bench With this microbenchmark we can measure the overhead of emulating atomic instructions with a configurable degree of contention. The benchmark spawns $n threads, each performing $o atomic ops (additions) in a loop. Each atomic operation is performed on a different cache line (assuming lines are 64b long) that is randomly selected from a range [0, $r). [ Note: each $foo corresponds to a -foo flag ] Signed-off-by: Emilio G. Cota Signed-off-by: Richard Henderson Message-Id: <1467054136-10430-20-git-send-email-cota@braap.org> --- tests/.gitignore | 1 + tests/Makefile.include | 4 +- tests/atomic_add-bench.c | 163 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 167 insertions(+), 1 deletion(-) create mode 100644 tests/atomic_add-bench.c diff --git a/tests/.gitignore b/tests/.gitignore index 4aec8bc5fa..64e050e859 100644 --- a/tests/.gitignore +++ b/tests/.gitignore @@ -1,3 +1,4 @@ +atomic_add-bench check-qdict check-qfloat check-qint diff --git a/tests/Makefile.include b/tests/Makefile.include index cd058efc14..22656eaf26 100644 --- a/tests/Makefile.include +++ b/tests/Makefile.include @@ -460,7 +460,8 @@ test-obj-y = tests/check-qint.o tests/check-qstring.o tests/check-qdict.o \ tests/test-opts-visitor.o tests/test-qmp-event.o \ tests/rcutorture.o tests/test-rcu-list.o \ tests/test-qdist.o \ - tests/test-qht.o tests/qht-bench.o tests/test-qht-par.o + tests/test-qht.o tests/qht-bench.o tests/test-qht-par.o \ + tests/atomic_add-bench.o $(test-obj-y): QEMU_INCLUDES += -Itests QEMU_CFLAGS += -I$(SRC_PATH)/tests @@ -507,6 +508,7 @@ tests/test-qht$(EXESUF): tests/test-qht.o $(test-util-obj-y) tests/test-qht-par$(EXESUF): tests/test-qht-par.o tests/qht-bench$(EXESUF) $(test-util-obj-y) tests/qht-bench$(EXESUF): tests/qht-bench.o $(test-util-obj-y) tests/test-bufferiszero$(EXESUF): tests/test-bufferiszero.o $(test-util-obj-y) +tests/atomic_add-bench$(EXESUF): tests/atomic_add-bench.o $(test-util-obj-y) tests/test-qdev-global-props$(EXESUF): tests/test-qdev-global-props.o \ hw/core/qdev.o hw/core/qdev-properties.o hw/core/hotplug.o\ diff --git a/tests/atomic_add-bench.c b/tests/atomic_add-bench.c new file mode 100644 index 0000000000..caa1e8e689 --- /dev/null +++ b/tests/atomic_add-bench.c @@ -0,0 +1,163 @@ +#include "qemu/osdep.h" +#include "qemu/thread.h" +#include "qemu/host-utils.h" +#include "qemu/processor.h" + +struct thread_info { + uint64_t r; +} QEMU_ALIGNED(64); + +struct count { + unsigned long val; +} QEMU_ALIGNED(64); + +static QemuThread *threads; +static struct thread_info *th_info; +static unsigned int n_threads = 1; +static unsigned int n_ready_threads; +static struct count *counts; +static unsigned int duration = 1; +static unsigned int range = 1024; +static bool test_start; +static bool test_stop; + +static const char commands_string[] = + " -n = number of threads\n" + " -d = duration in seconds\n" + " -r = range (will be rounded up to pow2)"; + +static void usage_complete(char *argv[]) +{ + fprintf(stderr, "Usage: %s [options]\n", argv[0]); + fprintf(stderr, "options:\n%s\n", commands_string); +} + +/* + * From: https://en.wikipedia.org/wiki/Xorshift + * This is faster than rand_r(), and gives us a wider range (RAND_MAX is only + * guaranteed to be >= INT_MAX). + */ +static uint64_t xorshift64star(uint64_t x) +{ + x ^= x >> 12; /* a */ + x ^= x << 25; /* b */ + x ^= x >> 27; /* c */ + return x * UINT64_C(2685821657736338717); +} + +static void *thread_func(void *arg) +{ + struct thread_info *info = arg; + + atomic_inc(&n_ready_threads); + while (!atomic_read(&test_start)) { + cpu_relax(); + } + + while (!atomic_read(&test_stop)) { + unsigned int index; + + info->r = xorshift64star(info->r); + index = info->r & (range - 1); + atomic_inc(&counts[index].val); + } + return NULL; +} + +static void run_test(void) +{ + unsigned int remaining; + unsigned int i; + + while (atomic_read(&n_ready_threads) != n_threads) { + cpu_relax(); + } + atomic_set(&test_start, true); + do { + remaining = sleep(duration); + } while (remaining); + atomic_set(&test_stop, true); + + for (i = 0; i < n_threads; i++) { + qemu_thread_join(&threads[i]); + } +} + +static void create_threads(void) +{ + unsigned int i; + + threads = g_new(QemuThread, n_threads); + th_info = g_new(struct thread_info, n_threads); + counts = qemu_memalign(64, sizeof(*counts) * range); + memset(counts, 0, sizeof(*counts) * range); + + for (i = 0; i < n_threads; i++) { + struct thread_info *info = &th_info[i]; + + info->r = (i + 1) ^ time(NULL); + qemu_thread_create(&threads[i], NULL, thread_func, info, + QEMU_THREAD_JOINABLE); + } +} + +static void pr_params(void) +{ + printf("Parameters:\n"); + printf(" # of threads: %u\n", n_threads); + printf(" duration: %u\n", duration); + printf(" ops' range: %u\n", range); +} + +static void pr_stats(void) +{ + unsigned long long val = 0; + unsigned int i; + double tx; + + for (i = 0; i < range; i++) { + val += counts[i].val; + } + tx = val / duration / 1e6; + + printf("Results:\n"); + printf("Duration: %u s\n", duration); + printf(" Throughput: %.2f Mops/s\n", tx); + printf(" Throughput/thread: %.2f Mops/s/thread\n", tx / n_threads); +} + +static void parse_args(int argc, char *argv[]) +{ + int c; + + for (;;) { + c = getopt(argc, argv, "hd:n:r:"); + if (c < 0) { + break; + } + switch (c) { + case 'h': + usage_complete(argv); + exit(0); + case 'd': + duration = atoi(optarg); + break; + case 'n': + n_threads = atoi(optarg); + break; + case 'r': + range = pow2ceil(atoi(optarg)); + break; + } + } +} + +int main(int argc, char *argv[]) +{ + parse_args(argc, argv); + pr_params(); + create_threads(); + run_test(); + pr_stats(); + return 0; +}