svn commit: r348548 - in vendor-sys/illumos/dist/uts/common/fs/zfs: . sys

[Alexander Motin]

Author: mav
Date: Mon Jun  3 16:57:06 2019
New Revision: 348548
URL: https://svnweb.freebsd.org/changeset/base/348548

Log:
  9617 too-frequent TXG sync causes excessive write inflation
  
  illumos/illumos-gate at 7928f4baf4ab3230557eb6289be68aa7a3003f38
  
  Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro at delphix.com>
  Reviewed by: Brad Lewis <brad.lewis at delphix.com>
  Reviewed by: George Wilson <george.wilson at delphix.com>
  Reviewed by: Andrew Stormont <andyjstormont at gmail.com>
  Approved by: Robert Mustacchi <rm at joyent.com>
  Author:     Matthew Ahrens <mahrens at delphix.com>

Modified:
  vendor-sys/illumos/dist/uts/common/fs/zfs/dsl_pool.c
  vendor-sys/illumos/dist/uts/common/fs/zfs/sys/dsl_pool.h
  vendor-sys/illumos/dist/uts/common/fs/zfs/txg.c

Modified: vendor-sys/illumos/dist/uts/common/fs/zfs/dsl_pool.c
==============================================================================
--- vendor-sys/illumos/dist/uts/common/fs/zfs/dsl_pool.c	Mon Jun  3 16:51:07 2019	(r348547)
+++ vendor-sys/illumos/dist/uts/common/fs/zfs/dsl_pool.c	Mon Jun  3 16:57:06 2019	(r348548)
@@ -103,9 +103,11 @@ uint64_t zfs_dirty_data_max_max = 4ULL * 1024 * 1024 *
 int zfs_dirty_data_max_percent = 10;
 
 /*
- * If there is at least this much dirty data, push out a txg.
+ * If there's at least this much dirty data (as a percentage of
+ * zfs_dirty_data_max), push out a txg.  This should be less than
+ * zfs_vdev_async_write_active_min_dirty_percent.
  */
-uint64_t zfs_dirty_data_sync = 64 * 1024 * 1024;
+uint64_t zfs_dirty_data_sync_pct = 20;
 
 /*
  * Once there is this amount of dirty data, the dmu_tx_delay() will kick in
@@ -824,10 +826,12 @@ 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_pct / 100;
 	boolean_t rv;
 
 	mutex_enter(&dp->dp_lock);
-	if (dp->dp_dirty_total > zfs_dirty_data_sync)
+	if (dp->dp_dirty_total > dirty_min_bytes)
 		txg_kick(dp);
 	rv = (dp->dp_dirty_total > delay_min_bytes);
 	mutex_exit(&dp->dp_lock);

Modified: vendor-sys/illumos/dist/uts/common/fs/zfs/sys/dsl_pool.h
==============================================================================
--- vendor-sys/illumos/dist/uts/common/fs/zfs/sys/dsl_pool.h	Mon Jun  3 16:51:07 2019	(r348547)
+++ vendor-sys/illumos/dist/uts/common/fs/zfs/sys/dsl_pool.h	Mon Jun  3 16:57:06 2019	(r348548)
@@ -53,7 +53,7 @@ struct dsl_scan;
 
 extern uint64_t zfs_dirty_data_max;
 extern uint64_t zfs_dirty_data_max_max;
-extern uint64_t zfs_dirty_data_sync;
+extern uint64_t zfs_dirty_data_sync_pct;
 extern int zfs_dirty_data_max_percent;
 extern int zfs_delay_min_dirty_percent;
 extern uint64_t zfs_delay_scale;

Modified: vendor-sys/illumos/dist/uts/common/fs/zfs/txg.c
==============================================================================
--- vendor-sys/illumos/dist/uts/common/fs/zfs/txg.c	Mon Jun  3 16:51:07 2019	(r348547)
+++ vendor-sys/illumos/dist/uts/common/fs/zfs/txg.c	Mon Jun  3 16:57:06 2019	(r348548)
@@ -484,6 +484,8 @@ txg_sync_thread(void *arg)
 		uint64_t timeout = zfs_txg_timeout * hz;
 		uint64_t timer;
 		uint64_t txg;
+		uint64_t dirty_min_bytes =
+		    zfs_dirty_data_max * zfs_dirty_data_sync_pct / 100;
 
 		/*
 		 * We sync when we're scanning, there's someone waiting
@@ -495,7 +497,7 @@ txg_sync_thread(void *arg)
 		    !tx->tx_exiting && timer > 0 &&
 		    tx->tx_synced_txg >= tx->tx_sync_txg_waiting &&
 		    !txg_has_quiesced_to_sync(dp) &&
-		    dp->dp_dirty_total < zfs_dirty_data_sync) {
+		    dp->dp_dirty_total < dirty_min_bytes) {
 			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);