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fat zap should prefetch when iterating

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When iterating over a ZAP object, we're almost always certain to iterate
over the entire object. If there are multiple leaf blocks, we can
realize a performance win by issuing reads for all the leaf blocks in
parallel when the iteration begins.

For example, if we have 10,000 snapshots, "zfs destroy -nv
pool/fs@1%9999" can take 30 minutes when the cache is cold. This change
provides a >3x performance improvement, by issuing the reads for all ~64
blocks of each ZAP object in parallel.

Reviewed-by: Andreas Dilger <andreas.dilger@whamcloud.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
External-issue: DLPX-58347
Closes #8862
This commit is contained in:
Matthew Ahrens
2019-06-12 13:13:09 -07:00
committed by Brian Behlendorf
parent d9cd66e45f
commit d9b4bf0665
6 changed files with 140 additions and 9 deletions
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module/zfs/zap_micro.c
+26 -5
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@@ -21,7 +21,7 @@
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2011, 2017 by Delphix. All rights reserved.
* Copyright (c) 2011, 2018 by Delphix. All rights reserved.
* Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
* Copyright 2017 Nexenta Systems, Inc.
*/
@@ -1472,9 +1472,9 @@ zap_remove_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
* Routines for iterating over the attributes.
*/
void
zap_cursor_init_serialized(zap_cursor_t *zc, objset_t *os, uint64_t zapobj,
uint64_t serialized)
static void
zap_cursor_init_impl(zap_cursor_t *zc, objset_t *os, uint64_t zapobj,
uint64_t serialized, boolean_t prefetch)
{
zc->zc_objset = os;
zc->zc_zap = NULL;
@@ -1483,12 +1483,33 @@ zap_cursor_init_serialized(zap_cursor_t *zc, objset_t *os, uint64_t zapobj,
zc->zc_serialized = serialized;
zc->zc_hash = 0;
zc->zc_cd = 0;
zc->zc_prefetch = prefetch;
}
void
zap_cursor_init_serialized(zap_cursor_t *zc, objset_t *os, uint64_t zapobj,
uint64_t serialized)
{
zap_cursor_init_impl(zc, os, zapobj, serialized, B_TRUE);
}
/*
* Initialize a cursor at the beginning of the ZAP object. The entire
* ZAP object will be prefetched.
*/
void
zap_cursor_init(zap_cursor_t *zc, objset_t *os, uint64_t zapobj)
{
zap_cursor_init_serialized(zc, os, zapobj, 0);
zap_cursor_init_impl(zc, os, zapobj, 0, B_TRUE);
}
/*
* Initialize a cursor at the beginning, but request that we not prefetch
* the entire ZAP object.
*/
void
zap_cursor_init_noprefetch(zap_cursor_t *zc, objset_t *os, uint64_t zapobj)
{
zap_cursor_init_impl(zc, os, zapobj, 0, B_FALSE);
}
void