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Date:      Tue, 20 Jan 2015 13:09:12 +0000 (UTC)
From:      Alexander Motin <mav@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r277419 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs
Message-ID:  <201501201309.t0KD9Cid002762@svn.freebsd.org>
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Author: mav
Date: Tue Jan 20 13:09:12 2015
New Revision: 277419
URL: https://svnweb.freebsd.org/changeset/base/277419

Log:
  Allow skipping dmu_buf_will_dirty() call in dsl_dir_transfer_space().
  
  dsl_dir_transfer_space() is mostly called after dsl_dir_diduse_space(),
  which already calls dmu_buf_will_dirty() for the same dbuf and tx, so
  its duplicate call in those cases will change nothing, only spend time.
  
  Skipping this call by four times reduces time spent in dbuf_write_done()
  and descendants, updating dataset statistics with several congested lock
  acquisitions.  When rewriting 8K zvol blocks at 1GB/s rate, this reduces
  CPU time spent inside dbuf_write_done(), according to profiling, from 45%
  of 683K samples to 18% of 422K.
  
  MFC after:	2 weeks

Modified:
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dir.c

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c	Tue Jan 20 12:28:24 2015	(r277418)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c	Tue Jan 20 13:09:12 2015	(r277419)
@@ -136,7 +136,7 @@ dsl_dataset_block_born(dsl_dataset_t *ds
 	dsl_dir_diduse_space(ds->ds_dir, DD_USED_HEAD, delta,
 	    compressed, uncompressed, tx);
 	dsl_dir_transfer_space(ds->ds_dir, used - delta,
-	    DD_USED_REFRSRV, DD_USED_HEAD, tx);
+	    DD_USED_REFRSRV, DD_USED_HEAD, NULL);
 }
 
 int
@@ -179,7 +179,7 @@ dsl_dataset_block_kill(dsl_dataset_t *ds
 		dsl_dir_diduse_space(ds->ds_dir, DD_USED_HEAD,
 		    delta, -compressed, -uncompressed, tx);
 		dsl_dir_transfer_space(ds->ds_dir, -used - delta,
-		    DD_USED_REFRSRV, DD_USED_HEAD, tx);
+		    DD_USED_REFRSRV, DD_USED_HEAD, NULL);
 	} else {
 		dprintf_bp(bp, "putting on dead list: %s", "");
 		if (async) {
@@ -2837,7 +2837,7 @@ dsl_dataset_clone_swap_sync_impl(dsl_dat
 		    origin_head->ds_dir->dd_origin_txg, UINT64_MAX,
 		    &odl_used, &odl_comp, &odl_uncomp);
 		dsl_dir_transfer_space(origin_head->ds_dir, cdl_used - odl_used,
-		    DD_USED_HEAD, DD_USED_SNAP, tx);
+		    DD_USED_HEAD, DD_USED_SNAP, NULL);
 	}
 
 	/* swap ds_*_bytes */

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dir.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dir.c	Tue Jan 20 12:28:24 2015	(r277418)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dir.c	Tue Jan 20 13:09:12 2015	(r277419)
@@ -1389,7 +1389,7 @@ dsl_dir_diduse_space(dsl_dir_t *dd, dd_u
 		    accounted_delta, compressed, uncompressed, tx);
 		dsl_dir_transfer_space(dd->dd_parent,
 		    used - accounted_delta,
-		    DD_USED_CHILD_RSRV, DD_USED_CHILD, tx);
+		    DD_USED_CHILD_RSRV, DD_USED_CHILD, NULL);
 	}
 }
 
@@ -1397,7 +1397,7 @@ void
 dsl_dir_transfer_space(dsl_dir_t *dd, int64_t delta,
     dd_used_t oldtype, dd_used_t newtype, dmu_tx_t *tx)
 {
-	ASSERT(dmu_tx_is_syncing(tx));
+	ASSERT(tx == NULL || dmu_tx_is_syncing(tx));
 	ASSERT(oldtype < DD_USED_NUM);
 	ASSERT(newtype < DD_USED_NUM);
 
@@ -1405,7 +1405,8 @@ dsl_dir_transfer_space(dsl_dir_t *dd, in
 	    !(dsl_dir_phys(dd)->dd_flags & DD_FLAG_USED_BREAKDOWN))
 		return;
 
-	dmu_buf_will_dirty(dd->dd_dbuf, tx);
+	if (tx != NULL)
+		dmu_buf_will_dirty(dd->dd_dbuf, tx);
 	mutex_enter(&dd->dd_lock);
 	ASSERT(delta > 0 ?
 	    dsl_dir_phys(dd)->dd_used_breakdown[oldtype] >= delta :

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