OpenZFS 7968 - multi-threaded spa_sync()

Reviewed by: Pavel Zakharov <[email protected]>
Reviewed by: Brad Lewis <[email protected]>
Reviewed by: Saso Kiselkov <[email protected]>
Reviewed by: Brian Behlendorf <[email protected]>
Ported-by: Matthew Ahrens <[email protected]>

spa_sync() iterates over all the dirty dnodes and processes each of them
by calling dnode_sync(). If there are many dirty dnodes (e.g. because we
created or removed a lot of files), the single thread of spa_sync()
calling dnode_sync() can become a bottleneck. Additionally, if many
dnodes are dirtied concurrently in open context (e.g. due to concurrent
file creation), the os_lock will experience lock contention via
dnode_setdirty().

The solution is to track dirty dnodes on a multilist_t, and for
spa_sync() to use separate threads to process each of the sublists in
the multilist.

OpenZFS-issue: https://www.illumos.org/issues/7968
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4a2a54c
Closes #5752 

1 files changed, 2 insertions, 2 deletions

diff --git a/include/sys/multilist.h b/include/sys/multilist.h
index 9b19d016d..439540685 100644
--- a/include/sys/multilist.h
+++ b/include/sys/multilist.h
@@ -72,8 +72,7 @@ struct multilist {
 };
 
 void multilist_destroy(multilist_t *);
-void multilist_create(multilist_t *, size_t, size_t,
-    multilist_sublist_index_func_t *);
+multilist_t *multilist_create(size_t, size_t, multilist_sublist_index_func_t *);
 
 void multilist_insert(multilist_t *, void *);
 void multilist_remove(multilist_t *, void *);
@@ -83,6 +82,7 @@ unsigned int multilist_get_num_sublists(multilist_t *);
 unsigned int multilist_get_random_index(multilist_t *);
 
 multilist_sublist_t *multilist_sublist_lock(multilist_t *, unsigned int);
+multilist_sublist_t *multilist_sublist_lock_obj(multilist_t *, void *);
 void multilist_sublist_unlock(multilist_sublist_t *);
 
 void multilist_sublist_insert_head(multilist_sublist_t *, void *);