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, 25 insertions, 2 deletions

diff --git a/cddl/contrib/opensolaris/cmd/zdb/zdb.c b/cddl/contrib/opensolaris/cmd/zdb/zdb.c
index 1fce5b6..c2c47d5 100644
--- a/cddl/contrib/opensolaris/cmd/zdb/zdb.c
+++ b/cddl/contrib/opensolaris/cmd/zdb/zdb.c
@@ -77,9 +77,11 @@
 #ifndef lint
 extern boolean_t zfs_recover;
 extern uint64_t zfs_arc_max, zfs_arc_meta_limit;
+extern int zfs_vdev_async_read_max_active;
 #else
 boolean_t zfs_recover;
 uint64_t zfs_arc_max, zfs_arc_meta_limit;
+int zfs_vdev_async_read_max_active;
 #endif
 
 const char cmdname[] = "zdb";
@@ -2384,8 +2386,14 @@ zdb_blkptr_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
 
 	zcb->zcb_readfails = 0;
 
-	if (dump_opt['b'] < 5 &&
-	    gethrtime() > zcb->zcb_lastprint + NANOSEC) {
+	/* only call gethrtime() every 100 blocks */
+	static int iters;
+	if (++iters > 100)
+		iters = 0;
+	else
+		return (0);
+
+	if (dump_opt['b'] < 5 && gethrtime() > zcb->zcb_lastprint + NANOSEC) {
 		uint64_t now = gethrtime();
 		char buf[10];
 		uint64_t bytes = zcb->zcb_type[ZB_TOTAL][ZDB_OT_TOTAL].zb_asize;
@@ -2494,6 +2502,14 @@ zdb_leak_init(spa_t *spa, zdb_cb_t *zcb)
 					    (longlong_t)vd->vdev_ms_count);
 
 					msp->ms_ops = &zdb_metaslab_ops;
+
+					/*
+					 * We don't want to spend the CPU
+					 * manipulating the size-ordered
+					 * tree, so clear the range_tree
+					 * ops.
+					 */
+					msp->ms_tree->rt_ops = NULL;
 					VERIFY0(space_map_load(msp->ms_sm,
 					    msp->ms_tree, SM_ALLOC));
 					msp->ms_loaded = B_TRUE;
@@ -3508,6 +3524,13 @@ main(int argc, char **argv)
 	 */
 	zfs_arc_max = zfs_arc_meta_limit = 256 * 1024 * 1024;
 
+	/*
+	 * "zdb -c" uses checksum-verifying scrub i/os which are async reads.
+	 * "zdb -b" uses traversal prefetch which uses async reads.
+	 * For good performance, let several of them be active at once.
+	 */
+	zfs_vdev_async_read_max_active = 10;
+
 	kernel_init(FREAD);
 	g_zfs = libzfs_init();
 	ASSERT(g_zfs != NULL);