MFC r268859: MFV r268851:

When a sync task is waiting for a txg to complete, we should hurry it along
by increasing the number of outstanding async writes (i.e. make
vdev_queue_max_async_writes() return a larger number).

Illumos issue:
    4753 increase number of outstanding async writes when sync task is waiting

1 files changed, 19 insertions, 1 deletions

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/txg.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/txg.c
index 0201bef..83c6b5f76 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/txg.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/txg.c
@@ -21,7 +21,7 @@
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Portions Copyright 2011 Martin Matuska <mm@FreeBSD.org>
- * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
  */
 
 #include <sys/zfs_context.h>
@@ -727,6 +727,24 @@ txg_list_empty(txg_list_t *tl, uint64_t txg)
 }
 
 /*
+ * Returns true if all txg lists are empty.
+ *
+ * Warning: this is inherently racy (an item could be added immediately after this
+ * function returns). We don't bother with the lock because it wouldn't change the
+ * semantics.
+ */
+boolean_t
+txg_all_lists_empty(txg_list_t *tl)
+{
+	for (int i = 0; i < TXG_SIZE; i++) {
+		if (!txg_list_empty(tl, i)) {
+			return (B_FALSE);
+		}
+	}
+	return (B_TRUE);
+}
+
+/*
  * Add an entry to the list (unless it's already on the list).
  * Returns B_TRUE if it was actually added.
  */