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Allow txg_kick() even there is a txg still syncing #11929

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Allow txg_kick() even there is a txg still syncing #11929

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184f4cd
Allow txg_kick() even there is a txg still syncing
jxdking Apr 22, 2021
6b40c56
Maximize txg size to improve throughput
jxdking Apr 30, 2021
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1 change: 1 addition & 0 deletions include/sys/dsl_pool.h
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Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,7 @@ struct dsl_deadlist;
extern unsigned long zfs_dirty_data_max;
extern unsigned long zfs_dirty_data_max_max;
extern int zfs_dirty_data_sync_percent;
extern unsigned long zfs_txg_quiesce_advance;
extern int zfs_dirty_data_max_percent;
extern int zfs_dirty_data_max_max_percent;
extern int zfs_delay_min_dirty_percent;
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2 changes: 1 addition & 1 deletion include/sys/txg.h
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,7 @@ extern void txg_register_callbacks(txg_handle_t *txghp, list_t *tx_callbacks);

extern void txg_delay(struct dsl_pool *dp, uint64_t txg, hrtime_t delta,
hrtime_t resolution);
extern void txg_kick(struct dsl_pool *dp);
extern void txg_kick(struct dsl_pool *dp, uint64_t txg);

/*
* Wait until the given transaction group has finished syncing.
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54 changes: 48 additions & 6 deletions module/zfs/dsl_pool.c
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Original file line number Diff line number Diff line change
Expand Up @@ -111,6 +111,16 @@ int zfs_dirty_data_max_max_percent = 25;
*/
int zfs_dirty_data_sync_percent = 20;

/*
* The open txg can be quiesced into the pipeline even there is a txg still
* syncing. When the dirty data in syncing txg is below
* zfs_txg_quiesce_advance, which also measns the sync is about to complete,
* quiesce the open txg into the pipeline.
* 0 means only quiesce the open txg when all the data in the previous txg
* is synced.
*/
unsigned long zfs_txg_quiesce_advance = 0;

/*
* Once there is this amount of dirty data, the dmu_tx_delay() will kick in
* and delay each transaction.
Expand Down Expand Up @@ -899,26 +909,46 @@ dsl_pool_need_dirty_delay(dsl_pool_t *dp)
{
uint64_t delay_min_bytes =
zfs_dirty_data_max * zfs_delay_min_dirty_percent / 100;
uint64_t dirty_min_bytes =
zfs_dirty_data_max * zfs_dirty_data_sync_percent / 100;
uint64_t dirty;

mutex_enter(&dp->dp_lock);
dirty = dp->dp_dirty_total;
uint64_t dirty = dp->dp_dirty_total;
mutex_exit(&dp->dp_lock);
if (dirty > dirty_min_bytes)
txg_kick(dp);

return (dirty > delay_min_bytes);
}

static boolean_t
dsl_pool_need_dirty_sync(dsl_pool_t *dp, uint64_t txg)
{
ASSERT(MUTEX_HELD(&dp->dp_lock));

uint64_t dirty_min_bytes =
zfs_dirty_data_max * zfs_dirty_data_sync_percent / 100;
uint64_t dirty = dp->dp_dirty_pertxg[txg & TXG_MASK];
uint64_t total = dp->dp_dirty_total;

/*
* Only quiesce new transaction group when previous syncing is
* getting close to completion, so that quiescing completed just
* in time for it. That's the time when the dirty data in
* syncing txg shrinks below zfs_txg_quiesce_advance.
*/
return (dirty > dirty_min_bytes &&
total - dirty <= zfs_txg_quiesce_advance);
}

void
dsl_pool_dirty_space(dsl_pool_t *dp, int64_t space, dmu_tx_t *tx)
{
if (space > 0) {
mutex_enter(&dp->dp_lock);
dp->dp_dirty_pertxg[tx->tx_txg & TXG_MASK] += space;
dsl_pool_dirty_delta(dp, space);
boolean_t needsync = dsl_pool_need_dirty_sync(dp, tx->tx_txg);
mutex_exit(&dp->dp_lock);

if (needsync)
txg_kick(dp, tx->tx_txg);
}
}

Expand All @@ -938,7 +968,16 @@ dsl_pool_undirty_space(dsl_pool_t *dp, int64_t space, uint64_t txg)
dp->dp_dirty_pertxg[txg & TXG_MASK] -= space;
ASSERT3U(dp->dp_dirty_total, >=, space);
dsl_pool_dirty_delta(dp, -space);

/* Assuming txg + 1 is in open stage, check if it needs to be synced. */
boolean_t needsync = dsl_pool_need_dirty_sync(dp, txg + 1);
mutex_exit(&dp->dp_lock);
/*
* Pass txg + 1 into txg_kick. Inside txg_kick(), it will kick only
* if txg + 1 is actually in open stage.
*/
if (needsync)
txg_kick(dp, txg + 1);
}

/* ARGSUSED */
Expand Down Expand Up @@ -1400,6 +1439,9 @@ ZFS_MODULE_PARAM(zfs, zfs_, dirty_data_max_max, ULONG, ZMOD_RD,
ZFS_MODULE_PARAM(zfs, zfs_, dirty_data_sync_percent, INT, ZMOD_RW,
"Dirty data txg sync threshold as a percentage of zfs_dirty_data_max");

ZFS_MODULE_PARAM(zfs, zfs_, txg_quiesce_advance, ULONG, ZMOD_RW,
"Threshold of the dirty data in syncing txg to quiesce open txg");

ZFS_MODULE_PARAM(zfs, zfs_, delay_scale, ULONG, ZMOD_RW,
"How quickly delay approaches infinity");

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38 changes: 17 additions & 21 deletions module/zfs/txg.c
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Original file line number Diff line number Diff line change
Expand Up @@ -498,14 +498,6 @@ txg_wait_callbacks(dsl_pool_t *dp)
taskq_wait_outstanding(tx->tx_commit_cb_taskq, 0);
}

static boolean_t
txg_is_syncing(dsl_pool_t *dp)
{
tx_state_t *tx = &dp->dp_tx;
ASSERT(MUTEX_HELD(&tx->tx_sync_lock));
return (tx->tx_syncing_txg != 0);
}

static boolean_t
txg_is_quiescing(dsl_pool_t *dp)
{
Expand Down Expand Up @@ -539,8 +531,6 @@ txg_sync_thread(void *arg)
clock_t timeout = zfs_txg_timeout * hz;
clock_t timer;
uint64_t txg;
uint64_t dirty_min_bytes =
zfs_dirty_data_max * zfs_dirty_data_sync_percent / 100;

/*
* We sync when we're scanning, there's someone waiting
Expand All @@ -551,8 +541,7 @@ txg_sync_thread(void *arg)
while (!dsl_scan_active(dp->dp_scan) &&
!tx->tx_exiting && timer > 0 &&
tx->tx_synced_txg >= tx->tx_sync_txg_waiting &&
!txg_has_quiesced_to_sync(dp) &&
dp->dp_dirty_total < dirty_min_bytes) {
!txg_has_quiesced_to_sync(dp)) {
dprintf("waiting; tx_synced=%llu waiting=%llu dp=%p\n",
tx->tx_synced_txg, tx->tx_sync_txg_waiting, dp);
txg_thread_wait(tx, &cpr, &tx->tx_sync_more_cv, timer);
Expand All @@ -565,9 +554,11 @@ txg_sync_thread(void *arg)
* prompting it to do so if necessary.
*/
while (!tx->tx_exiting && !txg_has_quiesced_to_sync(dp)) {
if (tx->tx_quiesce_txg_waiting < tx->tx_open_txg+1)
tx->tx_quiesce_txg_waiting = tx->tx_open_txg+1;
cv_broadcast(&tx->tx_quiesce_more_cv);
if (!txg_is_quiescing(dp)) {
if (tx->tx_quiesce_txg_waiting < tx->tx_open_txg + 1)
tx->tx_quiesce_txg_waiting = tx->tx_open_txg + 1;
cv_broadcast(&tx->tx_quiesce_more_cv);
}
txg_thread_wait(tx, &cpr, &tx->tx_quiesce_done_cv, 0);
}

Expand Down Expand Up @@ -784,22 +775,27 @@ txg_wait_open(dsl_pool_t *dp, uint64_t txg, boolean_t should_quiesce)
}

/*
* If there isn't a txg syncing or in the pipeline, push another txg through
* the pipeline by quiescing the open txg.
* If there isn't a txg quiescing in the pipeline, push the txg
* through the pipeline by quiescing the open txg.
* It is fine there is a txg still syncing.
* Pass in the txg number of the transaction that should be closed and synced.
*/
void
txg_kick(dsl_pool_t *dp)
txg_kick(dsl_pool_t *dp, uint64_t txg)
{
tx_state_t *tx = &dp->dp_tx;

ASSERT(!dsl_pool_config_held(dp));

if (txg != tx->tx_open_txg ||
tx->tx_quiesce_txg_waiting > tx->tx_open_txg)
return;

mutex_enter(&tx->tx_sync_lock);
if (!txg_is_syncing(dp) &&
if (txg == tx->tx_open_txg &&
!txg_is_quiescing(dp) &&
tx->tx_quiesce_txg_waiting <= tx->tx_open_txg &&
tx->tx_sync_txg_waiting <= tx->tx_synced_txg &&
tx->tx_quiesced_txg <= tx->tx_synced_txg) {
tx->tx_sync_txg_waiting <= tx->tx_synced_txg) {
tx->tx_quiesce_txg_waiting = tx->tx_open_txg + 1;
cv_broadcast(&tx->tx_quiesce_more_cv);
}
Expand Down