Code optimization and performance tweaking"

Modified dsl_pool_wrlog_delay().Signed-off-by: jxdking <lostking2008@hotmail.com>

module/zfs/dsl_pool.c

@@ -612,10 +612,15 @@ dsl_pool_dirty_delta(dsl_pool_t *dp, int64_t delta)
 void
 dsl_pool_wrlog_delay(int64_t size, dsl_pool_t *dp, uint64_t txg)
 {
+	ASSERT3S(size, >=, 0);
+	ASSERT3U(txg, >=, TXG_INITIAL);
+
 	uint64_t last_total;
+	uint64_t txg_total;
 
 	mutex_enter(&dp->dp_wrlog_lock);
 	last_total = dp->dp_wrlog_total;
+	txg_total = dp->dp_wrlog_pertxg[txg & TXG_MASK];
 	dp->dp_wrlog_total += size;
 	dp->dp_wrlog_pertxg[txg & TXG_MASK] += size;
 	mutex_exit(&dp->dp_wrlog_lock);
@@ -625,18 +630,26 @@ dsl_pool_wrlog_delay(int64_t size, dsl_pool_t *dp, uint64_t txg)
 		    "dp_wrlog_total: %llu", last_total);
 
 		/*
-		 * Current txg need to stay open to process current
-		 * write transaction. We only can wait until txg - 1
-		 * is synced.
+		 * Current txg needs to stay open to process current
+		 * write transaction. Under heavy load, persumably txg - 2
+		 * is one syncing. Wait on it.
 		 */
-		if (txg > 2) {
-			txg_wait_synced(dp, txg - 1);
-		}
+		txg_wait_synced(dp, txg - 2);
 	}
 
 	if (last_total >=
 	    zfs_wrlog_data_sync_percent * zfs_wrlog_data_max / 100) {
-		txg_kick(dp);
+		if (txg_total == last_total) {
+			// All data is in current txg, push it out
+			txg_kick(dp);
+		} else if (txg_total >= zfs_wrlog_data_max / 3) {
+			/*
+			 * There is some data in previous txgs that are
+			 * not synced yet. Hold it until current txg
+			 * is 1/3 full as zfs_wrlog_data_max.
+			 */
+			txg_kick(dp);
+		}
 	}
 }
 
@@ -649,7 +662,7 @@ dsl_pool_wrlog_clear(dsl_pool_t *dp, uint64_t txg)
 	mutex_exit(&dp->dp_wrlog_lock);
 
 	dprintf("write log total cleared for txg: %llu, "
-	    "dp_wrlog_total: %llu", txg, dp->dp_wrlog_total);
+	    "remaining dp_wrlog_total: %llu", txg, dp->dp_wrlog_total);
 }
 
 #ifdef ZFS_DEBUG