Maximize txg size to improve throughput

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 previous txg's dirty size shrinks to about 5% of dp_dirty_total. (current txg takes 95% of dp_dirty_total) Some other style fixes regarding code review. Signed-off-by: jxdking <[email protected]>
openzfs · May 13, 2021 · e474b3a · e474b3a
1 parent 184f4cd
commit e474b3a
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Showing 3 changed files with 15 additions and 8 deletions.
diff --git a/module/zfs/dmu_tx.c b/module/zfs/dmu_tx.c
@@ -1056,9 +1056,8 @@ dmu_tx_assign(dmu_tx_t *tx, uint64_t txg_how)
 
 	txg_rele_to_quiesce(&tx->tx_txgh);
 
-	if (dsl_pool_need_dirty_sync(tx->tx_pool, tx->tx_txg)) {
+	if (dsl_pool_need_dirty_sync(tx->tx_pool, tx->tx_txg))
 		txg_kick(tx->tx_pool, tx->tx_txg);
-	}
 	return (0);
 }
 

diff --git a/module/zfs/dsl_pool.c b/module/zfs/dsl_pool.c
@@ -899,10 +899,9 @@ 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;
 
 	mutex_enter(&dp->dp_lock);
-	dirty = dp->dp_dirty_total;
+	uint64_t dirty = dp->dp_dirty_total;
 	mutex_exit(&dp->dp_lock);
 
 	return (dirty > delay_min_bytes);
@@ -911,15 +910,23 @@ dsl_pool_need_dirty_delay(dsl_pool_t *dp)
 boolean_t
 dsl_pool_need_dirty_sync(dsl_pool_t *dp, uint64_t txg)
 {
-	uint64_t dirty;
 	uint64_t dirty_min_bytes =
 	    zfs_dirty_data_max * zfs_dirty_data_sync_percent / 100;
 
 	mutex_enter(&dp->dp_lock);
-	dirty = dp->dp_dirty_pertxg[txg & TXG_MASK];
+	uint64_t dirty = dp->dp_dirty_pertxg[txg & TXG_MASK];
+	uint64_t total = dp->dp_dirty_total;
 	mutex_exit(&dp->dp_lock);
 
-	return (dirty > dirty_min_bytes);
+	/*
+	 * 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 previous txg's dirty size
+	 * shrinks to about 5% of dp_dirty_total (current txg takes 95%
+	 * of dp_dirty_total)
+	 */
+	return (dirty > dirty_min_bytes &&
+	    dirty * 100 > total *  95);
 }
 
 void

diff --git a/module/zfs/txg.c b/module/zfs/txg.c
@@ -779,6 +779,7 @@ txg_wait_open(dsl_pool_t *dp, uint64_t txg, boolean_t should_quiesce)
  * 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, uint64_t txg)
@@ -788,7 +789,7 @@ txg_kick(dsl_pool_t *dp, uint64_t txg)
 	ASSERT(!dsl_pool_config_held(dp));
 
 	mutex_enter(&tx->tx_sync_lock);
-	txg = txg == 0 ? tx->tx_open_txg : txg;
+	txg = (txg == 0 ? tx->tx_open_txg : txg);
 	if (txg == tx->tx_open_txg &&
 	    !txg_is_quiescing(dp) &&
 	    tx->tx_quiesce_txg_waiting <= tx->tx_open_txg &&