svn commit: r349381 - in head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs: . sys

[Alexander Motin]

Author: mav
Date: Tue Jun 25 18:35:23 2019
New Revision: 349381
URL: https://svnweb.freebsd.org/changeset/base/349381

Log:
  Avoid extra taskq_dispatch() calls by DMU.
  
  DMU sync code calls taskq_dispatch() for each sublist of os_dirty_dnodes
  and os_synced_dnodes.  Since the number of sublists by default is equal
  to number of CPUs, it will dispatch equal, potentially large, number of
  tasks, waking up many CPUs to handle them, even if only one or few of
  sublists actually have any work to do.
  
  This change adds check for empty sublists to avoid this.

Modified:
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/multilist.c
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/multilist.h

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c	Tue Jun 25 18:13:39 2019	(r349380)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c	Tue Jun 25 18:35:23 2019	(r349381)
@@ -1334,6 +1334,8 @@ dmu_objset_sync(objset_t *os, zio_t *pio, dmu_tx_t *tx
 	zio_t *zio;
 	list_t *list;
 	dbuf_dirty_record_t *dr;
+	int num_sublists;
+	multilist_t *ml;
 	blkptr_t *blkptr_copy = kmem_alloc(sizeof (*os->os_rootbp), KM_SLEEP);
 	*blkptr_copy = *os->os_rootbp;
 
@@ -1402,10 +1404,13 @@ dmu_objset_sync(objset_t *os, zio_t *pio, dmu_tx_t *tx
 		}
 	}
 
-	for (int i = 0;
-	    i < multilist_get_num_sublists(os->os_dirty_dnodes[txgoff]); i++) {
+	ml = os->os_dirty_dnodes[txgoff];
+	num_sublists = multilist_get_num_sublists(ml);
+	for (int i = 0; i < num_sublists; i++) {
+		if (multilist_sublist_is_empty_idx(ml, i))
+			continue;
 		sync_dnodes_arg_t *sda = kmem_alloc(sizeof (*sda), KM_SLEEP);
-		sda->sda_list = os->os_dirty_dnodes[txgoff];
+		sda->sda_list = ml;
 		sda->sda_sublist_idx = i;
 		sda->sda_tx = tx;
 		(void) taskq_dispatch(dmu_objset_pool(os)->dp_sync_taskq,
@@ -1619,6 +1624,8 @@ userquota_updates_task(void *arg)
 void
 dmu_objset_do_userquota_updates(objset_t *os, dmu_tx_t *tx)
 {
+	int num_sublists;
+
 	if (!dmu_objset_userused_enabled(os))
 		return;
 
@@ -1632,8 +1639,10 @@ dmu_objset_do_userquota_updates(objset_t *os, dmu_tx_t
 		    DMU_OT_USERGROUP_USED, DMU_OT_NONE, 0, tx));
 	}
 
-	for (int i = 0;
-	    i < multilist_get_num_sublists(os->os_synced_dnodes); i++) {
+	num_sublists = multilist_get_num_sublists(os->os_synced_dnodes);
+	for (int i = 0; i < num_sublists; i++) {
+		if (multilist_sublist_is_empty_idx(os->os_synced_dnodes, i))
+			continue;
 		userquota_updates_arg_t *uua =
 		    kmem_alloc(sizeof (*uua), KM_SLEEP);
 		uua->uua_os = os;

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/multilist.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/multilist.c	Tue Jun 25 18:13:39 2019	(r349380)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/multilist.c	Tue Jun 25 18:35:23 2019	(r349381)
@@ -360,6 +360,28 @@ multilist_sublist_remove(multilist_sublist_t *mls, voi
 	list_remove(&mls->mls_list, obj);
 }
 
+int
+multilist_sublist_is_empty(multilist_sublist_t *mls)
+{
+	ASSERT(MUTEX_HELD(&mls->mls_lock));
+	return (list_is_empty(&mls->mls_list));
+}
+
+int
+multilist_sublist_is_empty_idx(multilist_t *ml, unsigned int sublist_idx)
+{
+	multilist_sublist_t *mls;
+	int empty;
+
+	ASSERT3U(sublist_idx, <, ml->ml_num_sublists);
+	mls = &ml->ml_sublists[sublist_idx];
+	ASSERT(!MUTEX_HELD(&mls->mls_lock));
+	mutex_enter(&mls->mls_lock);
+	empty = list_is_empty(&mls->mls_list);
+	mutex_exit(&mls->mls_lock);
+	return (empty);
+}
+
 void *
 multilist_sublist_head(multilist_sublist_t *mls)
 {

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/multilist.h
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/multilist.h	Tue Jun 25 18:13:39 2019	(r349380)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/multilist.h	Tue Jun 25 18:35:23 2019	(r349381)
@@ -89,6 +89,8 @@ void multilist_sublist_insert_head(multilist_sublist_t
 void multilist_sublist_insert_tail(multilist_sublist_t *, void *);
 void multilist_sublist_move_forward(multilist_sublist_t *mls, void *obj);
 void multilist_sublist_remove(multilist_sublist_t *, void *);
+int  multilist_sublist_is_empty(multilist_sublist_t *);
+int  multilist_sublist_is_empty_idx(multilist_t *, unsigned int);
 
 void *multilist_sublist_head(multilist_sublist_t *);
 void *multilist_sublist_tail(multilist_sublist_t *);