MFC r274276: MFV r274271:

Improve zdb -b performance:

 - Reduce gethrtime() call to 1/100th of blkptr's;
 - Skip manipulating the size-ordered tree;
 - Issue more (10, previously 3) async reads;
 - Use lighter weight testing in traverse_visitbp();

Illumos issue:
    5243 zdb -b could be much faster

1 files changed, 22 insertions, 19 deletions

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_traverse.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_traverse.c
index fb1ec07..5836549 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_traverse.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_traverse.c
@@ -59,6 +59,7 @@ typedef struct traverse_data {
 	int td_flags;
 	prefetch_data_t *td_pfd;
 	boolean_t td_paused;
+	uint64_t td_hole_birth_enabled_txg;
 	blkptr_cb_t *td_func;
 	void *td_arg;
 } traverse_data_t;
@@ -229,25 +230,20 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 	}
 
 	if (bp->blk_birth == 0) {
-		if (spa_feature_is_active(td->td_spa, SPA_FEATURE_HOLE_BIRTH)) {
-			/*
-			 * Since this block has a birth time of 0 it must be a
-			 * hole created before the SPA_FEATURE_HOLE_BIRTH
-			 * feature was enabled.  If SPA_FEATURE_HOLE_BIRTH
-			 * was enabled before the min_txg for this traveral we
-			 * know the hole must have been created before the
-			 * min_txg for this traveral, so we can skip it. If
-			 * SPA_FEATURE_HOLE_BIRTH was enabled after the min_txg
-			 * for this traveral we cannot tell if the hole was
-			 * created before or after the min_txg for this
-			 * traversal, so we cannot skip it.
-			 */
-			uint64_t hole_birth_enabled_txg;
-			VERIFY(spa_feature_enabled_txg(td->td_spa,
-			    SPA_FEATURE_HOLE_BIRTH, &hole_birth_enabled_txg));
-			if (hole_birth_enabled_txg < td->td_min_txg)
-				return (0);
-		}
+		/*
+		 * Since this block has a birth time of 0 it must be a
+		 * hole created before the SPA_FEATURE_HOLE_BIRTH
+		 * feature was enabled.  If SPA_FEATURE_HOLE_BIRTH
+		 * was enabled before the min_txg for this traveral we
+		 * know the hole must have been created before the
+		 * min_txg for this traveral, so we can skip it. If
+		 * SPA_FEATURE_HOLE_BIRTH was enabled after the min_txg
+		 * for this traveral we cannot tell if the hole was
+		 * created before or after the min_txg for this
+		 * traversal, so we cannot skip it.
+		 */
+		if (td->td_hole_birth_enabled_txg < td->td_min_txg)
+			return (0);
 	} else if (bp->blk_birth <= td->td_min_txg) {
 		return (0);
 	}
@@ -523,6 +519,13 @@ traverse_impl(spa_t *spa, dsl_dataset_t *ds, uint64_t objset, blkptr_t *rootbp,
 	td.td_flags = flags;
 	td.td_paused = B_FALSE;
 
+	if (spa_feature_is_active(spa, SPA_FEATURE_HOLE_BIRTH)) {
+		VERIFY(spa_feature_enabled_txg(spa,
+		    SPA_FEATURE_HOLE_BIRTH, &td.td_hole_birth_enabled_txg));
+	} else {
+		td.td_hole_birth_enabled_txg = 0;
+	}
+
 	pd.pd_blks_max = zfs_pd_blks_max;
 	pd.pd_flags = flags;
 	mutex_init(&pd.pd_mtx, NULL, MUTEX_DEFAULT, NULL);