On Tue, Feb 11, 2014 at 01:28:01AM +0200, Marti Raudsepp wrote:
> On Tue, Feb 11, 2014 at 12:20 AM, Marti Raudsepp <marti@xxxxxxxxx> wrote:
> > This is on Ubuntu 13.10 (kernel 3.11) with XFS (mount ed with noatime,
> > no other customizations).
>
> I managed to track this down; XFS doesn't allow using O_DIRECT for
> writes smaller than the filesystem's sector size (probably same on
> other FSes). The XFS filesystem created by the Ubuntu installer uses
> 4kB sectors, for some weird reason:
I have added the attached, applied C comment about Direct I/O write
failures and mismatched block sizes.
--
Bruce Momjian <bruce@xxxxxxxxxx> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ Everyone has their own god. +
diff --git a/contrib/pg_test_fsync/pg_test_fsync.c b/contrib/pg_test_fsync/pg_test_fsync.c
new file mode 100644
index 669c419..682821a
*** a/contrib/pg_test_fsync/pg_test_fsync.c
--- b/contrib/pg_test_fsync/pg_test_fsync.c
*************** test_sync(int writes_per_op)
*** 369,374 ****
--- 369,380 ----
{
for (writes = 0; writes < writes_per_op; writes++)
if (write(tmpfile, buf, XLOG_BLCKSZ) != XLOG_BLCKSZ)
+ /*
+ * This can generate write failures if the filesystem
+ * has a large block size, e.g. 4k, and there is no
+ * support for O_DIRECT writes smaller than the
+ * file system block size, e.g. XFS.
+ */
die("write failed");
if (lseek(tmpfile, 0, SEEK_SET) == -1)
die("seek failed");
--
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