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Speed up 'zfs list -t snapshot -o name -s name'

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FreeBSD #xxx:  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

NOTE: This patch only appears in FreeBSD.  If/when Illumos picks up
the change we may want to drop this patch and adopt their version.
However, for now this addresses a real issue.

Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #450
This commit is contained in:
Pawel Jakub Dawidek
2012-05-29 10:50:50 -07:00
committed by Brian Behlendorf
parent 74497b7ab6
commit 0cee24064a
8 changed files with 85 additions and 18 deletions
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module/zfs/zfs_ioctl.c
+3 -2
View File
@@ -21,6 +21,7 @@
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Portions Copyright 2011 Martin Matuska
* Portions Copyright 2012 Pawel Jakub Dawidek <pawel@dawidek.net>
* Copyright (c) 2012, Joyent, Inc. All rights reserved.
*/
@@ -1973,7 +1974,7 @@ zfs_ioc_snapshot_list_next(zfs_cmd_t *zc)
int error;
top:
if (zc->zc_cookie == 0)
if (zc->zc_cookie == 0 && !zc->zc_simple)
(void) dmu_objset_find(zc->zc_name, dmu_objset_prefetch,
NULL, DS_FIND_SNAPSHOTS);
@@ -1995,7 +1996,7 @@ top:
zc->zc_name + strlen(zc->zc_name), &zc->zc_obj, &zc->zc_cookie,
NULL);
if (error == 0) {
if (error == 0 && !zc->zc_simple) {
dsl_dataset_t *ds;
dsl_pool_t *dp = os->os_dsl_dataset->ds_dir->dd_pool;