Author: avg
Date: Tue Feb 21 21:09:21 2017
New Revision: 314058
URL: https://svnweb.freebsd.org/changeset/base/314058
Log:
zfs: lower priority of zio_write_issue threads by four
The difference of one was insignificant because zio_write_issue threads
ended up on the same run queues as other zio threads.
See sys/priority.h and sys/runq.h for more details.
Add a comment describing FreeBSD priority considerations and restore
the illumos variant of the code for comparison.
Obtained from: Panzura
MFC after: 2 weeks
Sponsored by: Panzura
Modified:
head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c
Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c Tue Feb 21
21:06:12 2017 (r314057)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c Tue Feb 21
21:09:21 2017 (r314058)
@@ -922,9 +922,17 @@ spa_taskqs_init(spa_t *spa, zio_type_t t
* The write issue taskq can be extremely CPU
* intensive. Run it at slightly lower priority
* than the other taskqs.
+ * FreeBSD notes:
+ * - numerically higher priorities are lower priorities;
+ * - if priorities divided by four (RQ_PPQ) are equal
+ * then a difference between them is insignificant.
*/
if (t == ZIO_TYPE_WRITE && q == ZIO_TASKQ_ISSUE)
- pri++;
+#ifdef illumos
+ pri--;
+#else
+ pri += 4;
+#endif
tq = taskq_create_proc(name, value, pri, 50,
INT_MAX, spa->spa_proc, flags);
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