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Prefetch on deadlists merge. #14402

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merged 1 commit into from
Jan 25, 2023
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Prefetch on deadlists merge. #14402

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1 change: 1 addition & 0 deletions include/sys/bpobj.h
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Original file line number Diff line number Diff line change
Expand Up @@ -87,6 +87,7 @@ int livelist_bpobj_iterate_from_nofree(bpobj_t *bpo, bpobj_itor_t func,
void *arg, int64_t start);

void bpobj_enqueue_subobj(bpobj_t *bpo, uint64_t subobj, dmu_tx_t *tx);
void bpobj_prefetch_subobj(bpobj_t *bpo, uint64_t subobj);
void bpobj_enqueue(bpobj_t *bpo, const blkptr_t *bp, boolean_t bp_freed,
dmu_tx_t *tx);

Expand Down
65 changes: 63 additions & 2 deletions module/zfs/bpobj.c
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Expand Up @@ -663,14 +663,13 @@ bpobj_enqueue_subobj(bpobj_t *bpo, uint64_t subobj, dmu_tx_t *tx)
}

VERIFY3U(0, ==, bpobj_open(&subbpo, bpo->bpo_os, subobj));
VERIFY3U(0, ==, bpobj_space(&subbpo, &used, &comp, &uncomp));

if (bpobj_is_empty(&subbpo)) {
/* No point in having an empty subobj. */
bpobj_close(&subbpo);
bpobj_free(bpo->bpo_os, subobj, tx);
return;
}
VERIFY3U(0, ==, bpobj_space(&subbpo, &used, &comp, &uncomp));

mutex_enter(&bpo->bpo_lock);
dmu_buf_will_dirty(bpo->bpo_dbuf, tx);
Expand Down Expand Up @@ -780,6 +779,68 @@ bpobj_enqueue_subobj(bpobj_t *bpo, uint64_t subobj, dmu_tx_t *tx)

}

/*
* Prefetch metadata required for bpobj_enqueue_subobj().
*/
void
bpobj_prefetch_subobj(bpobj_t *bpo, uint64_t subobj)
{
dmu_object_info_t doi;
bpobj_t subbpo;
uint64_t subsubobjs;
boolean_t copy_subsub = B_TRUE;
boolean_t copy_bps = B_TRUE;

ASSERT(bpobj_is_open(bpo));
ASSERT(subobj != 0);

if (subobj == dmu_objset_pool(bpo->bpo_os)->dp_empty_bpobj)
return;

if (bpobj_open(&subbpo, bpo->bpo_os, subobj) != 0)
return;
if (bpobj_is_empty(&subbpo)) {
bpobj_close(&subbpo);
return;
}
subsubobjs = subbpo.bpo_phys->bpo_subobjs;
bpobj_close(&subbpo);

if (subsubobjs != 0) {
if (dmu_object_info(bpo->bpo_os, subsubobjs, &doi) != 0)
return;
if (doi.doi_max_offset > doi.doi_data_block_size)
copy_subsub = B_FALSE;
}

if (dmu_object_info(bpo->bpo_os, subobj, &doi) != 0)
return;
if (doi.doi_max_offset > doi.doi_data_block_size || !copy_subsub)
copy_bps = B_FALSE;

if (copy_subsub && subsubobjs != 0) {
if (bpo->bpo_phys->bpo_subobjs) {
dmu_prefetch(bpo->bpo_os, bpo->bpo_phys->bpo_subobjs, 0,
bpo->bpo_phys->bpo_num_subobjs * sizeof (subobj), 1,
ZIO_PRIORITY_ASYNC_READ);
}
dmu_prefetch(bpo->bpo_os, subsubobjs, 0, 0, 1,
ZIO_PRIORITY_ASYNC_READ);
}

if (copy_bps) {
dmu_prefetch(bpo->bpo_os, bpo->bpo_object, 0,
bpo->bpo_phys->bpo_num_blkptrs * sizeof (blkptr_t), 1,
ZIO_PRIORITY_ASYNC_READ);
dmu_prefetch(bpo->bpo_os, subobj, 0, 0, 1,
ZIO_PRIORITY_ASYNC_READ);
} else if (bpo->bpo_phys->bpo_subobjs) {
dmu_prefetch(bpo->bpo_os, bpo->bpo_phys->bpo_subobjs, 0,
bpo->bpo_phys->bpo_num_subobjs * sizeof (subobj), 1,
ZIO_PRIORITY_ASYNC_READ);
}
}

void
bpobj_enqueue(bpobj_t *bpo, const blkptr_t *bp, boolean_t bp_freed,
dmu_tx_t *tx)
Expand Down
71 changes: 67 additions & 4 deletions module/zfs/dsl_deadlist.c
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Original file line number Diff line number Diff line change
Expand Up @@ -438,6 +438,18 @@ dle_enqueue_subobj(dsl_deadlist_t *dl, dsl_deadlist_entry_t *dle,
}
}

/*
* Prefetch metadata required for dle_enqueue_subobj().
*/
static void
dle_prefetch_subobj(dsl_deadlist_t *dl, dsl_deadlist_entry_t *dle,
uint64_t obj)
{
if (dle->dle_bpobj.bpo_object !=
dmu_objset_pool(dl->dl_os)->dp_empty_bpobj)
bpobj_prefetch_subobj(&dle->dle_bpobj, obj);
}

void
dsl_deadlist_insert(dsl_deadlist_t *dl, const blkptr_t *bp, boolean_t bp_freed,
dmu_tx_t *tx)
Expand Down Expand Up @@ -810,6 +822,27 @@ dsl_deadlist_insert_bpobj(dsl_deadlist_t *dl, uint64_t obj, uint64_t birth,
dle_enqueue_subobj(dl, dle, obj, tx);
}

/*
* Prefetch metadata required for dsl_deadlist_insert_bpobj().
*/
static void
dsl_deadlist_prefetch_bpobj(dsl_deadlist_t *dl, uint64_t obj, uint64_t birth)
{
dsl_deadlist_entry_t dle_tofind;
dsl_deadlist_entry_t *dle;
avl_index_t where;

ASSERT(MUTEX_HELD(&dl->dl_lock));

dsl_deadlist_load_tree(dl);

dle_tofind.dle_mintxg = birth;
dle = avl_find(&dl->dl_tree, &dle_tofind, &where);
if (dle == NULL)
dle = avl_nearest(&dl->dl_tree, where, AVL_BEFORE);
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dle_prefetch_subobj(dl, dle, obj);
}

static int
dsl_deadlist_insert_cb(void *arg, const blkptr_t *bp, boolean_t bp_freed,
dmu_tx_t *tx)
Expand All @@ -826,12 +859,12 @@ dsl_deadlist_insert_cb(void *arg, const blkptr_t *bp, boolean_t bp_freed,
void
dsl_deadlist_merge(dsl_deadlist_t *dl, uint64_t obj, dmu_tx_t *tx)
{
zap_cursor_t zc;
zap_attribute_t za;
zap_cursor_t zc, pzc;
zap_attribute_t za, pza;
dmu_buf_t *bonus;
dsl_deadlist_phys_t *dlp;
dmu_object_info_t doi;
int error;
int error, perror, i;

VERIFY0(dmu_object_info(dl->dl_os, obj, &doi));
if (doi.doi_type == DMU_OT_BPOBJ) {
Expand All @@ -843,15 +876,32 @@ dsl_deadlist_merge(dsl_deadlist_t *dl, uint64_t obj, dmu_tx_t *tx)
}

mutex_enter(&dl->dl_lock);
/*
* Prefetch up to 128 deadlists first and then more as we progress.
* The limit is a balance between ARC use and diminishing returns.
*/
for (zap_cursor_init(&pzc, dl->dl_os, obj), i = 0;
(perror = zap_cursor_retrieve(&pzc, &pza)) == 0 && i < 128;
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zap_cursor_advance(&pzc), i++) {
dsl_deadlist_prefetch_bpobj(dl, pza.za_first_integer,
zfs_strtonum(pza.za_name, NULL));
}
for (zap_cursor_init(&zc, dl->dl_os, obj);
(error = zap_cursor_retrieve(&zc, &za)) == 0;
zap_cursor_advance(&zc)) {
uint64_t mintxg = zfs_strtonum(za.za_name, NULL);
dsl_deadlist_insert_bpobj(dl, za.za_first_integer, mintxg, tx);
VERIFY0(zap_remove_int(dl->dl_os, obj, mintxg, tx));
if (perror == 0) {
dsl_deadlist_prefetch_bpobj(dl, pza.za_first_integer,
zfs_strtonum(pza.za_name, NULL));
zap_cursor_advance(&pzc);
perror = zap_cursor_retrieve(&pzc, &pza);
}
}
VERIFY3U(error, ==, ENOENT);
zap_cursor_fini(&zc);
zap_cursor_fini(&pzc);

VERIFY0(dmu_bonus_hold(dl->dl_os, obj, FTAG, &bonus));
dlp = bonus->db_data;
Expand All @@ -869,8 +919,9 @@ dsl_deadlist_move_bpobj(dsl_deadlist_t *dl, bpobj_t *bpo, uint64_t mintxg,
dmu_tx_t *tx)
{
dsl_deadlist_entry_t dle_tofind;
dsl_deadlist_entry_t *dle;
dsl_deadlist_entry_t *dle, *pdle;
avl_index_t where;
int i;

ASSERT(!dl->dl_oldfmt);

Expand All @@ -882,11 +933,23 @@ dsl_deadlist_move_bpobj(dsl_deadlist_t *dl, bpobj_t *bpo, uint64_t mintxg,
dle = avl_find(&dl->dl_tree, &dle_tofind, &where);
if (dle == NULL)
dle = avl_nearest(&dl->dl_tree, where, AVL_AFTER);
/*
* Prefetch up to 128 deadlists first and then more as we progress.
* The limit is a balance between ARC use and diminishing returns.
*/
for (pdle = dle, i = 0; pdle && i < 128; ) {
bpobj_prefetch_subobj(bpo, pdle->dle_bpobj.bpo_object);
pdle = AVL_NEXT(&dl->dl_tree, pdle);
}
while (dle) {
uint64_t used, comp, uncomp;
dsl_deadlist_entry_t *dle_next;

bpobj_enqueue_subobj(bpo, dle->dle_bpobj.bpo_object, tx);
if (pdle) {
bpobj_prefetch_subobj(bpo, pdle->dle_bpobj.bpo_object);
pdle = AVL_NEXT(&dl->dl_tree, pdle);
}

VERIFY0(bpobj_space(&dle->dle_bpobj,
&used, &comp, &uncomp));
Expand Down