K 10
svn:author
V 2
mm
K 8
svn:date
V 27
2012-02-20T21:10:14.207050Z
K 7
svn:log
V 810
MFC r230397, r230438:

MFC r230397 (pjd):
By default turn off prefetch when listing snapshots.
In my tests it makes listing snapshots 19% faster with cold cache and
47% faster with warm cache.

MFC r230438 (pjd):
Dramatically optimize listing snapshots when user requests only snapshot
names and wants to sort them by name, ie. when executes:

	# zfs list -t snapshot -o name -s name

Because only name is needed we don't have to read all snapshot properties.

Below you can find how long does it take to list 34509 snapshots from a single
disk pool before and after this change with cold and warm cache:

before:

	# time zfs list -t snapshot -o name -s name > /dev/null
	cold cache: 525s
	warm cache: 218s

after:

	# time zfs list -t snapshot -o name -s name > /dev/null
	cold cache: 1.7s
	warm cache: 1.1s

END