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Fast Clone Deletion

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Deleting a clone requires finding blocks are clone-only, not shared
with the snapshot. This was done by traversing the entire block tree
which results in a large performance penalty for sparsely
written clones.

This is new method keeps track of clone blocks when they are
modified in a "Livelist" so that, when it’s time to delete,
the clone-specific blocks are already at hand.

We see performance improvements because now deletion work is
proportional to the number of clone-modified blocks, not the size
of the original dataset.

Reviewed-by: Sean Eric Fagan <sef@ixsystems.com>
Reviewed-by: Matt Ahrens <matt@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com>
Signed-off-by: Sara Hartse <sara.hartse@delphix.com>
Closes #8416
This commit is contained in:
Sara Hartse
2019-07-26 10:54:14 -07:00
committed by Brian Behlendorf
parent d274ac5460
commit 37f03da8ba
38 changed files with 2583 additions and 205 deletions
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module/zfs/dbuf.c
+30
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@@ -3286,6 +3286,13 @@ dbuf_hold_impl_arg(struct dbuf_hold_arg *dh)
*(dh->dh_dbp) = NULL;
/* If the pool has been created, verify the tx_sync_lock is not held */
spa_t *spa = dh->dh_dn->dn_objset->os_spa;
dsl_pool_t *dp = spa->spa_dsl_pool;
if (dp != NULL) {
ASSERT(!MUTEX_HELD(&dp->dp_tx.tx_sync_lock));
}
/* dbuf_find() returns with db_mtx held */
dh->dh_db = dbuf_find(dh->dh_dn->dn_objset, dh->dh_dn->dn_object,
dh->dh_level, dh->dh_blkid);
@@ -4479,6 +4486,29 @@ dbuf_remap_impl(dnode_t *dn, blkptr_t *bp, krwlock_t *rw, dmu_tx_t *tx)
drica.drica_tx = tx;
if (spa_remap_blkptr(spa, &bp_copy, dbuf_remap_impl_callback,
&drica)) {
/*
* If the blkptr being remapped is tracked by a livelist,
* then we need to make sure the livelist reflects the update.
* First, cancel out the old blkptr by appending a 'FREE'
* entry. Next, add an 'ALLOC' to track the new version. This
* way we avoid trying to free an inaccurate blkptr at delete.
* Note that embedded blkptrs are not tracked in livelists.
*/
if (dn->dn_objset != spa_meta_objset(spa)) {
dsl_dataset_t *ds = dmu_objset_ds(dn->dn_objset);
if (dsl_deadlist_is_open(&ds->ds_dir->dd_livelist) &&
bp->blk_birth > ds->ds_dir->dd_origin_txg) {
ASSERT(!BP_IS_EMBEDDED(bp));
ASSERT(dsl_dir_is_clone(ds->ds_dir));
ASSERT(spa_feature_is_enabled(spa,
SPA_FEATURE_LIVELIST));
bplist_append(&ds->ds_dir->dd_pending_frees,
bp);
bplist_append(&ds->ds_dir->dd_pending_allocs,
&bp_copy);
}
}
/*
* The db_rwlock prevents dbuf_read_impl() from
* dereferencing the BP while we are changing it. To