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May 27, 2021
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Improve scrub maxinflight_bytes math. #12046

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2 changes: 1 addition & 1 deletion man/man5/zfs-module-parameters.5
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Original file line number Diff line number Diff line change
Expand Up @@ -3326,7 +3326,7 @@ Default value: \fB0\fR.
Maximum amount of data that can be concurrently issued at once for scrubs and
resilvers per leaf device, given in bytes.
.sp
Default value: \fB41943040\fR.
Default value: \fB4194304\fR.
.RE

.sp
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40 changes: 15 additions & 25 deletions module/zfs/dsl_scan.c
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Original file line number Diff line number Diff line change
Expand Up @@ -126,7 +126,7 @@ static boolean_t scan_ds_queue_contains(dsl_scan_t *scn, uint64_t dsobj,
static void scan_ds_queue_insert(dsl_scan_t *scn, uint64_t dsobj, uint64_t txg);
static void scan_ds_queue_remove(dsl_scan_t *scn, uint64_t dsobj);
static void scan_ds_queue_sync(dsl_scan_t *scn, dmu_tx_t *tx);
static uint64_t dsl_scan_count_leaves(vdev_t *vd);
static uint64_t dsl_scan_count_data_disks(vdev_t *vd);

extern int zfs_vdev_async_write_active_min_dirty_percent;

Expand Down Expand Up @@ -451,7 +451,7 @@ dsl_scan_init(dsl_pool_t *dp, uint64_t txg)
* phase are done per top-level vdev and are handled separately.
*/
scn->scn_maxinflight_bytes = MAX(zfs_scan_vdev_limit *
dsl_scan_count_leaves(spa->spa_root_vdev), 1ULL << 20);
dsl_scan_count_data_disks(spa->spa_root_vdev), 1ULL << 20);

avl_create(&scn->scn_queue, scan_ds_queue_compare, sizeof (scan_ds_t),
offsetof(scan_ds_t, sds_node));
Expand Down Expand Up @@ -2759,22 +2759,16 @@ dsl_scan_visit(dsl_scan_t *scn, dmu_tx_t *tx)
}

static uint64_t
dsl_scan_count_leaves(vdev_t *vd)
dsl_scan_count_data_disks(vdev_t *rvd)
{
uint64_t i, leaves = 0;

/* we only count leaves that belong to the main pool and are readable */
if (vd->vdev_islog || vd->vdev_isspare ||
vd->vdev_isl2cache || !vdev_readable(vd))
return (0);

if (vd->vdev_ops->vdev_op_leaf)
return (1);

for (i = 0; i < vd->vdev_children; i++) {
leaves += dsl_scan_count_leaves(vd->vdev_child[i]);
for (i = 0; i < rvd->vdev_children; i++) {
vdev_t *vd = rvd->vdev_child[i];
if (vd->vdev_islog || vd->vdev_isspare || vd->vdev_isl2cache)
continue;
leaves += vdev_get_ndisks(vd) - vdev_get_nparity(vd);
}

return (leaves);
}

Expand Down Expand Up @@ -3017,18 +3011,16 @@ scan_io_queues_run_one(void *arg)
range_seg_t *rs = NULL;
scan_io_t *sio = NULL;
list_t sio_list;
uint64_t bytes_per_leaf = zfs_scan_vdev_limit;
uint64_t nr_leaves = dsl_scan_count_leaves(queue->q_vd);

ASSERT(queue->q_scn->scn_is_sorted);

list_create(&sio_list, sizeof (scan_io_t),
offsetof(scan_io_t, sio_nodes.sio_list_node));
mutex_enter(q_lock);

/* calculate maximum in-flight bytes for this txg (min 1MB) */
queue->q_maxinflight_bytes =
MAX(nr_leaves * bytes_per_leaf, 1ULL << 20);
/* Calculate maximum in-flight bytes for this vdev. */
queue->q_maxinflight_bytes = MAX(1, zfs_scan_vdev_limit *
(vdev_get_ndisks(queue->q_vd) - vdev_get_nparity(queue->q_vd)));

/* reset per-queue scan statistics for this txg */
queue->q_total_seg_size_this_txg = 0;
Expand Down Expand Up @@ -3665,16 +3657,14 @@ dsl_scan_sync(dsl_pool_t *dp, dmu_tx_t *tx)
/* Need to scan metadata for more blocks to scrub */
dsl_scan_phys_t *scnp = &scn->scn_phys;
taskqid_t prefetch_tqid;
uint64_t bytes_per_leaf = zfs_scan_vdev_limit;
uint64_t nr_leaves = dsl_scan_count_leaves(spa->spa_root_vdev);

/*
* Recalculate the max number of in-flight bytes for pool-wide
* scanning operations (minimum 1MB). Limits for the issuing
* phase are done per top-level vdev and are handled separately.
*/
scn->scn_maxinflight_bytes =
MAX(nr_leaves * bytes_per_leaf, 1ULL << 20);
scn->scn_maxinflight_bytes = MAX(zfs_scan_vdev_limit *
dsl_scan_count_data_disks(spa->spa_root_vdev), 1ULL << 20);

if (scnp->scn_ddt_bookmark.ddb_class <=
scnp->scn_ddt_class_max) {
Expand Down Expand Up @@ -4050,9 +4040,8 @@ scan_exec_io(dsl_pool_t *dp, const blkptr_t *bp, int zio_flags,
size_t size = BP_GET_PSIZE(bp);
abd_t *data = abd_alloc_for_io(size, B_FALSE);

ASSERT3U(scn->scn_maxinflight_bytes, >, 0);

if (queue == NULL) {
ASSERT3U(scn->scn_maxinflight_bytes, >, 0);
mutex_enter(&spa->spa_scrub_lock);
while (spa->spa_scrub_inflight >= scn->scn_maxinflight_bytes)
cv_wait(&spa->spa_scrub_io_cv, &spa->spa_scrub_lock);
Expand All @@ -4061,6 +4050,7 @@ scan_exec_io(dsl_pool_t *dp, const blkptr_t *bp, int zio_flags,
} else {
kmutex_t *q_lock = &queue->q_vd->vdev_scan_io_queue_lock;

ASSERT3U(queue->q_maxinflight_bytes, >, 0);
mutex_enter(q_lock);
while (queue->q_inflight_bytes >= queue->q_maxinflight_bytes)
cv_wait(&queue->q_zio_cv, q_lock);
Expand Down