svn commit: r358312 - in stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs: . sys

[Alexander Motin]

Author: mav
Date: Tue Feb 25 15:52:35 2020
New Revision: 358312
URL: https://svnweb.freebsd.org/changeset/base/358312

Log:
  MFC r349381: 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:
  stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c
  stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/multilist.c
  stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/multilist.h
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c
==============================================================================
--- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c	Tue Feb 25 15:03:41 2020	(r358311)
+++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c	Tue Feb 25 15:52:35 2020	(r358312)
@@ -1353,6 +1353,8 @@ 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;
 
@@ -1421,10 +1423,13 @@ 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,
@@ -1640,6 +1645,8 @@ 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;
 
@@ -1653,8 +1660,10 @@ 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: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/multilist.c
==============================================================================
--- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/multilist.c	Tue Feb 25 15:03:41 2020	(r358311)
+++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/multilist.c	Tue Feb 25 15:52:35 2020	(r358312)
@@ -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: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/multilist.h
==============================================================================
--- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/multilist.h	Tue Feb 25 15:03:41 2020	(r358311)
+++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/multilist.h	Tue Feb 25 15:52:35 2020	(r358312)
@@ -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 *);