Increase default user space stack size

Under RHEL6/CentOS6 the default stack size must be increased to 32K
to prevent overflowing the stack when running ztest.  This isn't an
issue for other distributions due to either the version of pthreads
or perhaps the compiler.  Doubling the stack size resolves the
issue safely for all distribution and leaves us some headroom.

$ sudo -E ztest -V -T 300 -f /var/tmp/
5 vdevs, 7 datasets, 23 threads, 300 seconds...

loading space map for vdev 0 of 1, metaslab 0 of 30 ...
...
loading space map for vdev 0 of 1, metaslab 14 of 30 ...
child died with signal 11
Exited ztest with error 3

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #4215

diff --git a/include/sys/zfs_context.h b/include/sys/zfs_context.h
index a967c05679ee1f3f8796694d4e2666d226a84077..6ff4d4302304fc742cfcd25a185e8f3684d40be1 100644 (file)
--- a/include/sys/zfs_context.h
+++ b/include/sys/zfs_context.h
@@ -222,7 +222,7 @@ extern int aok;
  */
 #define        TS_MAGIC                0x72f158ab4261e538ull
 #define        TS_RUN                  0x00000002
-#define        TS_STACK_MIN            PTHREAD_STACK_MIN
+#define        TS_STACK_MIN            MAX(PTHREAD_STACK_MIN, 32768)
 #define        TS_STACK_MAX            (256 * 1024)
 
 /* in libzpool, p0 exists only to have its address taken */

diff --git a/man/man1/ztest.1 b/man/man1/ztest.1
index f798bcfcb8e8152493423b5b6dc41074dac7317f..ebfacd46dcb0ac613f99dfd6720156685ddea83f 100644 (file)
--- a/man/man1/ztest.1
+++ b/man/man1/ztest.1
@@ -149,11 +149,10 @@ ztest -f / -V -T 120
 .TP
 .B "ZFS_STACK_SIZE=stacksize"
 Limit the default stack size to \fBstacksize\fR bytes for the purpose of
-detecting and debugging kernel stack overflows.  For x86_64 platforms this
-value should be set as follows to simulate these platforms: \fB8192\fR
-(Linux), \fB20480\fR (Illumos), \fB16384\fR (FreeBSD).
+detecting and debugging kernel stack overflows.  This value defaults to
+\fB32K\fR which is double the default \fB16K\fR Linux kernel stack size.
 
-In practice you may need to set these value slightly higher because
+In practice, setting the stack size slightly higher is needed because
 differences in stack usage between kernel and user space can lead to spurious
 stack overflows (especially when debugging is enabled).  The specified value
 will be rounded up to a floor of PTHREAD_STACK_MIN which is the minimum stack

diff --git a/module/zfs/txg.c b/module/zfs/txg.c
index d5dff58abb772a40b4187ddde638cff25a0f0f0d..ed8007e052385dd944a147cf656de076247ceb36 100644 (file)
--- a/module/zfs/txg.c
+++ b/module/zfs/txg.c
@@ -212,7 +212,7 @@ txg_sync_start(dsl_pool_t *dp)
         * 32-bit x86.  This is due in part to nested pools and
         * scrub_visitbp() recursion.
         */
-       tx->tx_sync_thread = thread_create(NULL, 32<<10, txg_sync_thread,
+       tx->tx_sync_thread = thread_create(NULL, 0, txg_sync_thread,
            dp, 0, &p0, TS_RUN, defclsyspri);
 
        mutex_exit(&tx->tx_sync_lock);