t/read-to-pipe-async: Use the monotonic clock when measuring time intervals

Make the output independent of wall clock changes applied by e.g. ntpd.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>

diff --git a/t/read-to-pipe-async.c b/t/read-to-pipe-async.c
index 03fe9ea464bf3a25d9d93c0150f0663aa0f5f5d5..69799336e99e6fd92b31099de6fdadfe0dc4fc53 100644 (file)
--- a/t/read-to-pipe-async.c
+++ b/t/read-to-pipe-async.c
@@ -101,13 +101,13 @@ struct work_item {
 static struct reader_thread reader_thread;
 static struct writer_thread writer_thread;
 
-uint64_t utime_since(const struct timeval *s, const struct timeval *e)
+uint64_t utime_since(const struct timespec *s, const struct timespec *e)
 {
        long sec, usec;
        uint64_t ret;
 
        sec = e->tv_sec - s->tv_sec;
-       usec = e->tv_usec - s->tv_usec;
+       usec = (e->tv_nsec - s->tv_nsec) / 1000;
        if (sec > 0 && usec < 0) {
                sec--;
                usec += 1000000;
@@ -219,12 +219,12 @@ static void add_lat(struct stats *s, unsigned int us, const char *name)
 
 static int write_work(struct work_item *work)
 {
-       struct timeval s, e;
+       struct timespec s, e;
        ssize_t ret;
 
-       gettimeofday(&s, NULL);
+       clock_gettime(CLOCK_MONOTONIC, &s);
        ret = write(STDOUT_FILENO, work->buf, work->buf_size);
-       gettimeofday(&e, NULL);
+       clock_gettime(CLOCK_MONOTONIC, &e);
        assert(ret == work->buf_size);
 
        add_lat(&work->writer->s, utime_since(&s, &e), "write");
@@ -270,13 +270,13 @@ static void *writer_fn(void *data)
 
 static void reader_work(struct work_item *work)
 {
-       struct timeval s, e;
+       struct timespec s, e;
        ssize_t ret;
        size_t left;
        void *buf;
        off_t off;
 
-       gettimeofday(&s, NULL);
+       clock_gettime(CLOCK_MONOTONIC, &s);
 
        left = work->buf_size;
        buf = work->buf;
@@ -295,7 +295,7 @@ static void reader_work(struct work_item *work)
                buf += ret;
        }
 
-       gettimeofday(&e, NULL);
+       clock_gettime(CLOCK_MONOTONIC, &e);
 
        add_lat(&work->reader->s, utime_since(&s, &e), "read");
 
@@ -575,7 +575,7 @@ static void prune_done_entries(struct writer_thread *wt)
 int main(int argc, char *argv[])
 {
        pthread_condattr_t cattr;
-       struct timeval s, re, we;
+       struct timespec s, re, we;
        struct reader_thread *rt;
        struct writer_thread *wt;
        unsigned long rate;
@@ -626,7 +626,7 @@ int main(int argc, char *argv[])
        assert(ret == 0);
 #endif
 
-       gettimeofday(&s, NULL);
+       clock_gettime(CLOCK_MONOTONIC, &s);
 
        while (sb.st_size) {
                struct work_item *work;
@@ -673,10 +673,10 @@ int main(int argc, char *argv[])
        }
 
        exit_thread(&rt->thread, NULL, NULL);
-       gettimeofday(&re, NULL);
+       clock_gettime(CLOCK_MONOTONIC, &re);
 
        exit_thread(&wt->thread, prune_done_entries, wt);
-       gettimeofday(&we, NULL);
+       clock_gettime(CLOCK_MONOTONIC, &we);
 
        show_latencies(&rt->s, "READERS");
        show_latencies(&wt->s, "WRITERS");