ZIL: Improve write log size accounting

Before this change write log size TXG throttling mechanism was
accounting only user payload bytes.  But the actual ZIL both on
disk and especially in memory include headers of hundred(s) of
bytes.  Not accouting those may allow applications like
bonnie++, in their wisdom writing one byte at a time, to consume
excessive amount of memory and ZIL/SLOG in one TXG.

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Rob Norris <[email protected]>
Signed-off-by:	Alexander Motin <[email protected]>
Sponsored by:	iXsystems, Inc.
Closes #17373

Author: amotin

module/zfs/zfs_log.c

@@ -617,8 +617,7 @@ zfs_log_write(zilog_t *zilog, dmu_tx_t *tx, int txtype,
 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)sa_get_db(zp->z_sa_hdl);
 	uint32_t blocksize = zp->z_blksz;
 	itx_wr_state_t write_state;
-	uint64_t gen = 0;
-	ssize_t size = resid;
+	uint64_t gen = 0, log_size = 0;
 
 	if (zil_replaying(zilog, tx) || zp->z_unlinked ||
 	    zfs_xattr_owner_unlinked(zp)) {
@@ -680,6 +679,10 @@ zfs_log_write(zilog_t *zilog, dmu_tx_t *tx, int txtype,
 			}
 		}
 
+		log_size += itx->itx_size;
+		if (wr_state == WR_NEED_COPY)
+			log_size += len;
+
 		itx->itx_wr_state = wr_state;
 		lr->lr_foid = zp->z_id;
 		lr->lr_offset = off;
@@ -699,9 +702,7 @@ zfs_log_write(zilog_t *zilog, dmu_tx_t *tx, int txtype,
 		resid -= len;
 	}
 
-	if (write_state == WR_COPIED || write_state == WR_NEED_COPY) {
-		dsl_pool_wrlog_count(zilog->zl_dmu_pool, size, tx->tx_txg);
-	}
+	dsl_pool_wrlog_count(zilog->zl_dmu_pool, log_size, tx->tx_txg);
 }
 
 /*

module/zfs/zvol.c

@@ -871,7 +871,7 @@ zvol_log_write(zvol_state_t *zv, dmu_tx_t *tx, uint64_t offset,
 	uint32_t blocksize = zv->zv_volblocksize;
 	zilog_t *zilog = zv->zv_zilog;
 	itx_wr_state_t write_state;
-	uint64_t sz = size;
+	uint64_t log_size = 0;
 
 	if (zil_replaying(zilog, tx))
 		return;
@@ -909,6 +909,10 @@ zvol_log_write(zvol_state_t *zv, dmu_tx_t *tx, uint64_t offset,
 			wr_state = WR_NEED_COPY;
 		}
 
+		log_size += itx->itx_size;
+		if (wr_state == WR_NEED_COPY)
+			log_size += len;
+
 		itx->itx_wr_state = wr_state;
 		lr->lr_foid = ZVOL_OBJ;
 		lr->lr_offset = offset;
@@ -924,9 +928,7 @@ zvol_log_write(zvol_state_t *zv, dmu_tx_t *tx, uint64_t offset,
 		size -= len;
 	}
 
-	if (write_state == WR_COPIED || write_state == WR_NEED_COPY) {
-		dsl_pool_wrlog_count(zilog->zl_dmu_pool, sz, tx->tx_txg);
-	}
+	dsl_pool_wrlog_count(zilog->zl_dmu_pool, log_size, tx->tx_txg);
 }
 
 /*