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Re: bug#12820: gnulib testsuite failure in latest master
From: |
Paul Eggert |
Subject: |
Re: bug#12820: gnulib testsuite failure in latest master |
Date: |
Wed, 07 Nov 2012 23:44:49 -0800 |
User-agent: |
Mozilla/5.0 (X11; Linux i686; rv:16.0) Gecko/20121028 Thunderbird/16.0.2 |
Ouch, I read your strace output incorrectly: it was napping
for 20 ms, not 2 s. Still, there should be no need to nap
for that long; 1 ms should suffice on your platform.
I installed the following patch to cause the test
to take shorter naps. This might affect your original
problem, and might not (hey! it's a timing problem)
but at least it should make the test run faster.
>From b1af052298f85650d85ea37d24f59ab99ff56db8 Mon Sep 17 00:00:00 2001
From: Paul Eggert <address@hidden>
Date: Wed, 7 Nov 2012 23:36:43 -0800
Subject: [PATCH] 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
<http://bugs.gnu.org/12820#11>.
---
ChangeLog | 11 +++++++
tests/nap.h | 107 ++++++++++++++++++++++++++++++++++++++++--------------------
2 files changed, 83 insertions(+), 35 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 1a1e8b7..bd05f3c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2012-11-07 Paul Eggert <address@hidden>
+
+ 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
+ <http://bugs.gnu.org/12820#11>.
+
2012-11-07 Jim Meyering <address@hidden>
mountlist.c: fix a compilation failure
diff --git a/tests/nap.h b/tests/nap.h
index 6dfb0a0..99d47b6 100644
--- 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);
}
--
1.7.11.7
- Re: bug#12820: gnulib testsuite failure in latest master,
Paul Eggert <=