cpu clock: add independent test for monotonic/sane TSC
authorJens Axboe <axboe@kernel.dk>
Mon, 17 Dec 2012 11:03:29 +0000 (12:03 +0100)
committerJens Axboe <axboe@kernel.dk>
Mon, 17 Dec 2012 11:03:29 +0000 (12:03 +0100)
Fire up all threads on the system, checking the clock 100,000
times on each. Then collect and compare results, to ensure we
never have a clock that goes backwards.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
gettime.c
gettime.h
init.c

index 9f23e3f..bf35c71 100644 (file)
--- a/gettime.c
+++ b/gettime.c
@@ -11,6 +11,7 @@
 #include "smalloc.h"
 
 #include "hash.h"
+#include "os/os.h"
 
 #ifdef ARCH_HAVE_CPU_CLOCK
 static unsigned long cycles_per_usec;
@@ -347,3 +348,167 @@ unsigned long time_since_now(struct timeval *s)
 {
        return mtime_since_now(s) / 1000;
 }
+
+#if defined(FIO_HAVE_CPU_AFFINITY) && defined(ARCH_HAVE_CPU_CLOCK)
+
+#define CLOCK_ENTRIES  100000
+
+struct clock_entry {
+       unsigned long seq;
+       unsigned long tsc;
+       unsigned long cpu;
+};
+
+struct clock_thread {
+       pthread_t thread;
+       int cpu;
+       pthread_mutex_t lock;
+       pthread_mutex_t started;
+       uint64_t *seq;
+       struct clock_entry *entries;
+};
+
+static inline uint64_t atomic64_inc_return(uint64_t *seq)
+{
+       return 1 + __sync_fetch_and_add(seq, 1);
+}
+
+static void *clock_thread_fn(void *data)
+{
+       struct clock_thread *t = data;
+       struct clock_entry *c;
+       os_cpu_mask_t cpu_mask;
+       int i;
+
+       memset(&cpu_mask, 0, sizeof(cpu_mask));
+       fio_cpu_set(&cpu_mask, t->cpu);
+
+       if (fio_setaffinity(gettid(), cpu_mask) == -1) {
+               log_err("clock setaffinity failed\n");
+               return (void *) 1;
+       }
+
+       pthread_mutex_unlock(&t->started);
+       pthread_mutex_lock(&t->lock);
+
+       c = &t->entries[0];
+       for (i = 0; i < CLOCK_ENTRIES; i++, c++) {
+               uint64_t seq, tsc;
+
+               c->cpu = t->cpu;
+               do {
+                       seq = atomic64_inc_return(t->seq);
+                       tsc = get_cpu_clock();
+               } while (seq != *t->seq);
+
+               c->seq = seq;
+               c->tsc = tsc;
+       }
+
+       log_info("cs: cpu%3d: %lu clocks seen\n", t->cpu, t->entries[CLOCK_ENTRIES - 1].tsc - t->entries[0].tsc);
+       return NULL;
+}
+
+static int clock_cmp(const void *p1, const void *p2)
+{
+       const struct clock_entry *c1 = p1;
+       const struct clock_entry *c2 = p2;
+
+       return c1->seq - c2->seq;
+}
+
+int fio_monotonic_clocktest(void)
+{
+       struct clock_thread *threads;
+       unsigned int nr_cpus = cpus_online();
+       struct clock_entry *entries;
+       unsigned long tentries, failed;
+       uint64_t seq = 0;
+       int i;
+
+       threads = malloc(nr_cpus * sizeof(struct clock_thread));
+       tentries = CLOCK_ENTRIES * nr_cpus;
+       entries = malloc(tentries * sizeof(struct clock_entry));
+
+       log_info("cs: Testing %u CPUs\n", nr_cpus);
+
+       for (i = 0; i < nr_cpus; i++) {
+               struct clock_thread *t = &threads[i];
+
+               t->cpu = i;
+               t->seq = &seq;
+               t->entries = &entries[i * CLOCK_ENTRIES];
+               pthread_mutex_init(&t->lock, NULL);
+               pthread_mutex_init(&t->started, NULL);
+               pthread_mutex_lock(&t->lock);
+               pthread_create(&t->thread, NULL, clock_thread_fn, t);
+       }
+
+       for (i = 0; i < nr_cpus; i++) {
+               struct clock_thread *t = &threads[i];
+
+               pthread_mutex_lock(&t->started);
+       }
+
+       for (i = 0; i < nr_cpus; i++) {
+               struct clock_thread *t = &threads[i];
+
+               pthread_mutex_unlock(&t->lock);
+       }
+
+       for (failed = i = 0; i < nr_cpus; i++) {
+               struct clock_thread *t = &threads[i];
+               void *ret;
+
+               pthread_join(t->thread, &ret);
+               if (ret)
+                       failed++;
+       }
+       free(threads);
+
+       if (failed) {
+               log_err("Clocksource test: %u threads failed\n", failed);
+               goto err;
+       }
+
+       qsort(entries, tentries, sizeof(struct clock_entry), clock_cmp);
+
+       for (failed = i = 0; i < tentries; i++) {
+               struct clock_entry *prev, *this = &entries[i];
+
+               if (!i) {
+                       prev = this;
+                       continue;
+               }
+
+               if (prev->tsc > this->tsc) {
+                       uint64_t diff = prev->tsc - this->tsc;
+
+                       log_info("cs: CPU clock mismatch (diff=%lu):\n", diff);
+                       log_info("\t CPU%3lu: TSC=%lu, SEQ=%lu\n", prev->cpu, prev->tsc, prev->seq);
+                       log_info("\t CPU%3lu: TSC=%lu, SEQ=%lu\n", this->cpu, this->tsc, this->seq);
+                       failed++;
+               }
+
+               prev = this;
+       }
+
+       if (failed)
+               log_info("cs: Failed: %lu\n", failed);
+       else
+               log_info("cs: Pass!\n");
+
+err:
+       free(entries);
+       return !!failed;
+}
+
+#else /* defined(FIO_HAVE_CPU_AFFINITY) && defined(ARCH_HAVE_CPU_CLOCK) */
+
+int fio_monotonic_clocktest(void)
+{
+       log_info("cs: current platform does not support CPU clocks\n");
+       return 0;
+}
+
+#endif
index 64651a1..8ca3791 100644 (file)
--- a/gettime.h
+++ b/gettime.h
@@ -15,6 +15,7 @@ extern void fio_gettime(struct timeval *, void *);
 extern void fio_gtod_init(void);
 extern void fio_clock_init(void);
 extern int fio_start_gtod_thread(void);
+extern int fio_monotonic_clocktest(void);
 
 extern struct timeval *fio_tv;
 
diff --git a/init.c b/init.c
index e90d735..c894af3 100644 (file)
--- a/init.c
+++ b/init.c
@@ -207,6 +207,11 @@ static struct option l_opts[FIO_NR_OPTIONS] = {
                .has_arg        = required_argument,
                .val            = 'C',
        },
+       {
+               .name           = (char *) "cpuclock-test",
+               .has_arg        = no_argument,
+               .val            = 'T',
+       },
        {
                .name           = NULL,
        },
@@ -1621,6 +1626,10 @@ int parse_cmd_line(int argc, char *argv[])
                                optind++;
                        }
                        break;
+               case 'T':
+                       do_exit++;
+                       exit_val = fio_monotonic_clocktest();
+                       break;
                default:
                        do_exit++;
                        exit_val = 1;