5 files changed, 44 insertions, 31 deletions

diff --git a/uts/common/fs/zfs/arc.c b/uts/common/fs/zfs/arc.c
index 66bbfae52b40..bd1a64621b88 100644
--- a/uts/common/fs/zfs/arc.c
+++ b/uts/common/fs/zfs/arc.c
@@ -21,7 +21,7 @@
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2012, Joyent, Inc. All rights reserved.
- * Copyright (c) 2011, 2016 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2017 by Delphix. All rights reserved.
  * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
  * Copyright 2015 Nexenta Systems, Inc.  All rights reserved.
  */
@@ -296,13 +296,6 @@ uint_t arc_reduce_dnlc_percent = 3;
  */
 int zfs_arc_evict_batch_limit = 10;
 
-/*
- * The number of sublists used for each of the arc state lists. If this
- * is not set to a suitable value by the user, it will be configured to
- * the number of CPUs on the system in arc_init().
- */
-int zfs_arc_num_sublists_per_state = 0;
-
 /* number of seconds before growing cache again */
 static int		arc_grow_retry = 60;
 
@@ -5775,43 +5768,43 @@ arc_state_init(void)
 	multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA],
 	    sizeof (arc_buf_hdr_t),
 	    offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
-	    zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+	    arc_state_multilist_index_func);
 	multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA],
 	    sizeof (arc_buf_hdr_t),
 	    offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
-	    zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+	    arc_state_multilist_index_func);
 	multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA],
 	    sizeof (arc_buf_hdr_t),
 	    offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
-	    zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+	    arc_state_multilist_index_func);
 	multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA],
 	    sizeof (arc_buf_hdr_t),
 	    offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
-	    zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+	    arc_state_multilist_index_func);
 	multilist_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA],
 	    sizeof (arc_buf_hdr_t),
 	    offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
-	    zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+	    arc_state_multilist_index_func);
 	multilist_create(&arc_mfu->arcs_list[ARC_BUFC_DATA],
 	    sizeof (arc_buf_hdr_t),
 	    offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
-	    zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+	    arc_state_multilist_index_func);
 	multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA],
 	    sizeof (arc_buf_hdr_t),
 	    offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
-	    zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+	    arc_state_multilist_index_func);
 	multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA],
 	    sizeof (arc_buf_hdr_t),
 	    offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
-	    zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+	    arc_state_multilist_index_func);
 	multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA],
 	    sizeof (arc_buf_hdr_t),
 	    offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
-	    zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+	    arc_state_multilist_index_func);
 	multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA],
 	    sizeof (arc_buf_hdr_t),
 	    offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
-	    zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+	    arc_state_multilist_index_func);
 
 	refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
 	refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
@@ -5969,9 +5962,6 @@ arc_init(void)
 	if (zfs_arc_p_min_shift > 0)
 		arc_p_min_shift = zfs_arc_p_min_shift;
 
-	if (zfs_arc_num_sublists_per_state < 1)
-		zfs_arc_num_sublists_per_state = MAX(boot_ncpus, 1);
-
 	/* if kmem_flags are set, lets try to use less memory */
 	if (kmem_debugging())
 		arc_c = arc_c / 2;
diff --git a/uts/common/fs/zfs/dbuf.c b/uts/common/fs/zfs/dbuf.c
index 6000ba0fda0c..fed6810a2f68 100644
--- a/uts/common/fs/zfs/dbuf.c
+++ b/uts/common/fs/zfs/dbuf.c
@@ -623,7 +623,6 @@ retry:
 
 	multilist_create(&dbuf_cache, sizeof (dmu_buf_impl_t),
 	    offsetof(dmu_buf_impl_t, db_cache_link),
-	    zfs_arc_num_sublists_per_state,
 	    dbuf_cache_multilist_index_func);
 	refcount_create(&dbuf_cache_size);
 
diff --git a/uts/common/fs/zfs/multilist.c b/uts/common/fs/zfs/multilist.c
index 82960571bcb4..291a8d329e0c 100644
--- a/uts/common/fs/zfs/multilist.c
+++ b/uts/common/fs/zfs/multilist.c
@@ -13,7 +13,7 @@
  * CDDL HEADER END
  */
 /*
- * Copyright (c) 2013, 2014 by Delphix. All rights reserved.
+ * Copyright (c) 2013, 2017 by Delphix. All rights reserved.
  */
 
 #include <sys/zfs_context.h>
@@ -23,6 +23,12 @@
 #include <sys/spa.h>
 
 /*
+ * This overrides the number of sublists in each multilist_t, which defaults
+ * to the number of CPUs in the system (see multilist_create()).
+ */
+int zfs_multilist_num_sublists = 0;
+
+/*
  * Given the object contained on the list, return a pointer to the
  * object's multilist_node_t structure it contains.
  */
@@ -59,9 +65,9 @@ multilist_d2l(multilist_t *ml, void *obj)
  *     requirement, but a general rule of thumb in order to garner the
  *     best multi-threaded performance out of the data structure.
  */
-void
-multilist_create(multilist_t *ml, size_t size, size_t offset, unsigned int num,
-    multilist_sublist_index_func_t *index_func)
+static void
+multilist_create_impl(multilist_t *ml, size_t size, size_t offset,
+    unsigned int num, multilist_sublist_index_func_t *index_func)
 {
 	ASSERT3P(ml, !=, NULL);
 	ASSERT3U(size, >, 0);
@@ -86,6 +92,26 @@ multilist_create(multilist_t *ml, size_t size, size_t offset, unsigned int num,
 }
 
 /*
+ * Initialize a new sublist, using the default number of sublists
+ * (the number of CPUs, or at least 4, or the tunable
+ * zfs_multilist_num_sublists).
+ */
+void
+multilist_create(multilist_t *ml, size_t size, size_t offset,
+    multilist_sublist_index_func_t *index_func)
+{
+	int num_sublists;
+
+	if (zfs_multilist_num_sublists > 0) {
+		num_sublists = zfs_multilist_num_sublists;
+	} else {
+		num_sublists = MAX(boot_ncpus, 4);
+	}
+
+	multilist_create_impl(ml, size, offset, num_sublists, index_func);
+}
+
+/*
  * Destroy the given multilist object, and free up any memory it holds.
  */
 void
diff --git a/uts/common/fs/zfs/sys/arc.h b/uts/common/fs/zfs/sys/arc.h
index ad42cf7bcc9d..10c920ff9d97 100644
--- a/uts/common/fs/zfs/sys/arc.h
+++ b/uts/common/fs/zfs/sys/arc.h
@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2017 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
  */
 
@@ -64,8 +64,6 @@ typedef void arc_done_func_t(zio_t *zio, arc_buf_t *buf, void *private);
 arc_done_func_t arc_bcopy_func;
 arc_done_func_t arc_getbuf_func;
 
-extern int zfs_arc_num_sublists_per_state;
-
 typedef enum arc_flags
 {
 	/*
diff --git a/uts/common/fs/zfs/sys/multilist.h b/uts/common/fs/zfs/sys/multilist.h
index 5ebb7fe1a1d5..3f01b886c31c 100644
--- a/uts/common/fs/zfs/sys/multilist.h
+++ b/uts/common/fs/zfs/sys/multilist.h
@@ -13,7 +13,7 @@
  * CDDL HEADER END
  */
 /*
- * Copyright (c) 2013, 2014 by Delphix. All rights reserved.
+ * Copyright (c) 2013, 2017 by Delphix. All rights reserved.
  */
 
 #ifndef	_SYS_MULTILIST_H
@@ -73,7 +73,7 @@ struct multilist {
 };
 
 void multilist_destroy(multilist_t *);
-void multilist_create(multilist_t *, size_t, size_t, unsigned int,
+void multilist_create(multilist_t *, size_t, size_t,
     multilist_sublist_index_func_t *);
 
 void multilist_insert(multilist_t *, void *);