# HG changeset patch # User Paul Eggert # Date 1352360203 28800 # Node ID d20cbb4d40beef80469b31f3e1e3d767506b695c # Parent d6b976fe7362e659d79ab7d7774a6200b3258fa3 test-utimens: speed up by taking shorter naps * tests/nap.h (lt_mtime, get_mtime, nap_works, guess_delay): New functions. (nap): Use them, to do a better job of guessing the delay. On Fedora 17 with ext4 atop md atop hard disks, this made test-utimens run 10x faster, because the test napped for 1 ms at a time rather than 20 ms. Reported by Stefano Lattarini in . diff --git a/ChangeLog b/ChangeLog --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,14 @@ +2012-11-07 Paul Eggert + + test-utimens: speed up by taking shorter naps + * tests/nap.h (lt_mtime, get_mtime, nap_works, guess_delay): + New functions. + (nap): Use them, to do a better job of guessing the delay. + On Fedora 17 with ext4 atop md atop hard disks, this made + test-utimens run 10x faster, because the test napped for + 1 ms at a time rather than 20 ms. Reported by Stefano Lattarini in + . + 2012-11-07 Jim Meyering mountlist.c: fix a compilation failure diff --git a/tests/nap.h b/tests/nap.h --- a/tests/nap.h +++ b/tests/nap.h @@ -19,48 +19,85 @@ #ifndef GLTEST_NAP_H # define GLTEST_NAP_H +static int +lt_mtime (struct stat const *a, struct stat const *b) +{ + time_t as = a->st_mtime; + time_t bs = b->st_mtime; + int ans = get_stat_mtime_ns (a); + int bns = get_stat_mtime_ns (b); + + return as < bs || (as == bs && ans < bns); +} + +static void +get_mtime (int fd, struct stat *st, int do_write) +{ + if (do_write) + ASSERT (write (fd, "\n", 1) == 1); + ASSERT (fstat (fd, st) == 0); +} + +/* Given a file whose descriptor is FD, see whether delaying by DELAY + microseconds causes a change in a file's time stamp. If the time + stamps differ, repeat the test one more time, in case we crossed a + quantization boundary on a file system with lower resolution. *ST + is the file's status, recently gotten. Update *ST to reflect the + latest status gotten. */ +static int +nap_works (int fd, int delay, struct stat *st) +{ + struct stat old_st; + int result = 0; + old_st = *st; + usleep (delay); + get_mtime (fd, st, 1); + if (! lt_mtime (&old_st, st)) + return 0; + old_st = *st; + usleep (delay); + get_mtime (fd, st, 1); + return lt_mtime (&old_st, st); +} + +static int +guess_delay (void) +{ + /* Try a 1-microsecond sleep first, for speed. If that doesn't + work, try a 1 ms sleep; that should work with ext. If it doesn't + work, try a 20 ms sleep. xfs has a quantization of about 10 + milliseconds, even though it has a granularity of 1 nanosecond, + and NTFS has a default quantization of 15.25 milliseconds, even + though it has a granularity of 100 nanoseconds, so 20 ms is a + good quantization to try. If that doesn't work, try 1 second. + The worst case is 2 seconds, needed for FAT. */ + static int const delaytab[] = {1, 1000, 20000, 1000000 }; + int fd = creat (BASE "tmp", 0600); + int i; + int delay = 2000000; + struct stat st; + ASSERT (0 <= fd); + get_mtime (fd, &st, 0); + for (i = 0; i < sizeof delaytab / sizeof delaytab[0]; i++) + if (nap_works (fd, delaytab[i], &st)) + { + delay = delaytab[i]; + break; + } + ASSERT (close (fd) == 0); + ASSERT (unlink (BASE "tmp") == 0); + return delay; +} + /* Sleep long enough to notice a timestamp difference on the file system in the current directory. Assumes that BASE is defined, and requires that the test module depends on usleep. */ static void nap (void) { - static long delay; + static int delay; if (!delay) - { - /* Initialize only once, by sleeping for 20 milliseconds (needed - since xfs has a quantization of about 10 milliseconds, even - though it has a granularity of 1 nanosecond, and since NTFS - has a default quantization of 15.25 milliseconds, even though - it has a granularity of 100 nanoseconds). If the seconds - differ, repeat the test one more time (in case we crossed a - quantization boundary on a file system with 1 second - resolution). If we can't observe a difference in only the - nanoseconds, then fall back to 1 second if the time is odd, - and 2 seconds (needed for FAT) if time is even. */ - struct stat st1; - struct stat st2; - ASSERT (close (creat (BASE "tmp", 0600)) == 0); - ASSERT (stat (BASE "tmp", &st1) == 0); - ASSERT (unlink (BASE "tmp") == 0); - delay = 20000; - usleep (delay); - ASSERT (close (creat (BASE "tmp", 0600)) == 0); - ASSERT (stat (BASE "tmp", &st2) == 0); - ASSERT (unlink (BASE "tmp") == 0); - if (st1.st_mtime != st2.st_mtime) - { - /* Seconds differ, give it one more shot. */ - st1 = st2; - usleep (delay); - ASSERT (close (creat (BASE "tmp", 0600)) == 0); - ASSERT (stat (BASE "tmp", &st2) == 0); - ASSERT (unlink (BASE "tmp") == 0); - } - if (! (st1.st_mtime == st2.st_mtime - && get_stat_mtime_ns (&st1) < get_stat_mtime_ns (&st2))) - delay = (st1.st_mtime & 1) ? 1000000 : 2000000; - } + delay = guess_delay (); usleep (delay); }