BRT: Rework structures and locks to be per-vdev

While block cloning operation from the beginning was made per-vdev,
before this change most of its data were protected by two pool-
wide locks.  It created lots of lock contention in many workload.

This change makes most of block cloning data structures per-vdev,
which allows to lock them separately.  The only pool-wide lock now
it spa_brt_lock, protecting array of per-vdev pointers and in most
cases taken as reader.  Also this splits per-vdev locks into three
different ones: bv_pending_lock protects the AVL-tree of pending
operations in open context, bv_mos_entries_lock protects BRT ZAP
object from while being prefetched, and bv_lock protects the rest
of per-vdev context during TXG commit process.  There should be
no functional difference aside of some optimizations.

Signed-off-by:	Alexander Motin <[email protected]>
Sponsored by:	iXsystems, Inc.

cmd/zdb/zdb.c

@@ -2119,9 +2119,6 @@ dump_brt(spa_t *spa)
 		return;
 	}
 
-	brt_t *brt = spa->spa_brt;
-	VERIFY(brt);
-
 	char count[32], used[32], saved[32];
 	zdb_nicebytes(brt_get_used(spa), used, sizeof (used));
 	zdb_nicebytes(brt_get_saved(spa), saved, sizeof (saved));
@@ -2132,11 +2129,8 @@ dump_brt(spa_t *spa)
 	if (dump_opt['T'] < 2)
 		return;
 
-	for (uint64_t vdevid = 0; vdevid < brt->brt_nvdevs; vdevid++) {
-		brt_vdev_t *brtvd = &brt->brt_vdevs[vdevid];
-		if (brtvd == NULL)
-			continue;
-
+	for (uint64_t vdevid = 0; vdevid < spa->spa_brt_nvdevs; vdevid++) {
+		brt_vdev_t *brtvd = spa->spa_brt_vdevs[vdevid];
 		if (!brtvd->bv_initiated) {
 			printf("BRT: vdev %" PRIu64 ": empty\n", vdevid);
 			continue;
@@ -2160,20 +2154,21 @@ dump_brt(spa_t *spa)
 	if (!do_histo)
 		printf("\n%-16s %-10s\n", "DVA", "REFCNT");
 
-	for (uint64_t vdevid = 0; vdevid < brt->brt_nvdevs; vdevid++) {
-		brt_vdev_t *brtvd = &brt->brt_vdevs[vdevid];
-		if (brtvd == NULL || !brtvd->bv_initiated)
+	for (uint64_t vdevid = 0; vdevid < spa->spa_brt_nvdevs; vdevid++) {
+		brt_vdev_t *brtvd = spa->spa_brt_vdevs[vdevid];
+		if (!brtvd->bv_initiated)
 			continue;
 
 		uint64_t counts[64] = {};
 
 		zap_cursor_t zc;
 		zap_attribute_t *za = zap_attribute_alloc();
-		for (zap_cursor_init(&zc, brt->brt_mos, brtvd->bv_mos_entries);
+		for (zap_cursor_init(&zc, spa->spa_meta_objset,
+		    brtvd->bv_mos_entries);
 		    zap_cursor_retrieve(&zc, za) == 0;
 		    zap_cursor_advance(&zc)) {
 			uint64_t refcnt;
-			VERIFY0(zap_lookup_uint64(brt->brt_mos,
+			VERIFY0(zap_lookup_uint64(spa->spa_meta_objset,
 			    brtvd->bv_mos_entries,
 			    (const uint64_t *)za->za_name, 1,
 			    za->za_integer_length, za->za_num_integers,
@@ -8227,14 +8222,11 @@ dump_mos_leaks(spa_t *spa)
 		}
 	}
 
-	if (spa->spa_brt != NULL) {
-		brt_t *brt = spa->spa_brt;
-		for (uint64_t vdevid = 0; vdevid < brt->brt_nvdevs; vdevid++) {
-			brt_vdev_t *brtvd = &brt->brt_vdevs[vdevid];
-			if (brtvd != NULL && brtvd->bv_initiated) {
-				mos_obj_refd(brtvd->bv_mos_brtvdev);
-				mos_obj_refd(brtvd->bv_mos_entries);
-			}
+	for (uint64_t vdevid = 0; vdevid < spa->spa_brt_nvdevs; vdevid++) {
+		brt_vdev_t *brtvd = spa->spa_brt_vdevs[vdevid];
+		if (brtvd->bv_initiated) {
+			mos_obj_refd(brtvd->bv_mos_brtvdev);
+			mos_obj_refd(brtvd->bv_mos_entries);
 		}
 	}
 

include/sys/brt_impl.h

@@ -86,28 +86,38 @@ typedef struct brt_vdev_phys {
 	uint64_t	bvp_savedspace;
 } brt_vdev_phys_t;
 
-typedef struct brt_vdev {
+struct brt_vdev {
 	/*
-	 * VDEV id.
+	 * Pending changes from open contexts.
 	 */
-	uint64_t	bv_vdevid;
+	kmutex_t	bv_pending_lock;
+	avl_tree_t	bv_pending_tree[TXG_SIZE];
 	/*
-	 * Is the structure initiated?
-	 * (bv_entcount and bv_bitmap are allocated?)
+	 * Protects bv_mos_*.
 	 */
-	boolean_t	bv_initiated;
+	krwlock_t	bv_mos_entries_lock ____cacheline_aligned;
+	/*
+	 * Protects all the fields starting from bv_initiated.
+	 */
+	krwlock_t	bv_lock ____cacheline_aligned;
+	/*
+	 * VDEV id.
+	 */
+	uint64_t	bv_vdevid ____cacheline_aligned;
 	/*
 	 * Object number in the MOS for the entcount array and brt_vdev_phys.
 	 */
 	uint64_t	bv_mos_brtvdev;
 	/*
-	 * Object number in the MOS for the entries table.
+	 * Object number in the MOS and dnode for the entries table.
 	 */
 	uint64_t	bv_mos_entries;
+	dnode_t		*bv_mos_entries_dnode;
 	/*
-	 * Entries to sync.
+	 * Is the structure initiated?
+	 * (bv_entcount and bv_bitmap are allocated?)
 	 */
-	avl_tree_t	bv_tree;
+	boolean_t	bv_initiated;
 	/*
 	 * Does the bv_entcount[] array needs byte swapping?
 	 */
@@ -120,6 +130,26 @@ typedef struct brt_vdev {
 	 * This is the array with BRT entry count per BRT_RANGESIZE.
 	 */
 	uint16_t	*bv_entcount;
+	/*
+	 * bv_entcount[] potentially can be a bit too big to sychronize it all
+	 * when we just changed few entcounts. The fields below allow us to
+	 * track updates to bv_entcount[] array since the last sync.
+	 * A single bit in the bv_bitmap represents as many entcounts as can
+	 * fit into a single BRT_BLOCKSIZE.
+	 * For example we have 65536 entcounts in the bv_entcount array
+	 * (so the whole array is 128kB). We updated bv_entcount[2] and
+	 * bv_entcount[5]. In that case only first bit in the bv_bitmap will
+	 * be set and we will write only first BRT_BLOCKSIZE out of 128kB.
+	 */
+	ulong_t		*bv_bitmap;
+	/*
+	 * bv_entcount[] needs updating on disk.
+	 */
+	boolean_t	bv_entcount_dirty;
+	/*
+	 * brt_vdev_phys needs updating on disk.
+	 */
+	boolean_t	bv_meta_dirty;
 	/*
 	 * Sum of all bv_entcount[]s.
 	 */
@@ -133,45 +163,10 @@ typedef struct brt_vdev {
 	 */
 	uint64_t	bv_savedspace;
 	/*
-	 * brt_vdev_phys needs updating on disk.
-	 */
-	boolean_t	bv_meta_dirty;
-	/*
-	 * bv_entcount[] needs updating on disk.
-	 */
-	boolean_t	bv_entcount_dirty;
-	/*
-	 * bv_entcount[] potentially can be a bit too big to sychronize it all
-	 * when we just changed few entcounts. The fields below allow us to
-	 * track updates to bv_entcount[] array since the last sync.
-	 * A single bit in the bv_bitmap represents as many entcounts as can
-	 * fit into a single BRT_BLOCKSIZE.
-	 * For example we have 65536 entcounts in the bv_entcount array
-	 * (so the whole array is 128kB). We updated bv_entcount[2] and
-	 * bv_entcount[5]. In that case only first bit in the bv_bitmap will
-	 * be set and we will write only first BRT_BLOCKSIZE out of 128kB.
+	 * Entries to sync.
 	 */
-	ulong_t		*bv_bitmap;
-	uint64_t	bv_nblocks;
-} brt_vdev_t;
-
-/*
- * In-core brt
- */
-typedef struct brt {
-	krwlock_t	brt_lock;
-	spa_t		*brt_spa;
-#define	brt_mos		brt_spa->spa_meta_objset
-	uint64_t	brt_rangesize;
-	uint64_t	brt_usedspace;
-	uint64_t	brt_savedspace;
-	avl_tree_t	brt_pending_tree[TXG_SIZE];
-	kmutex_t	brt_pending_lock[TXG_SIZE];
-	/* Sum of all entries across all bv_trees. */
-	uint64_t	brt_nentries;
-	brt_vdev_t	*brt_vdevs;
-	uint64_t	brt_nvdevs;
-} brt_t;
+	avl_tree_t	bv_tree;
+};
 
 /* Size of bre_offset / sizeof (uint64_t). */
 #define	BRT_KEY_WORDS	(1)

include/sys/spa.h

@@ -53,6 +53,7 @@ extern "C" {
 /*
  * Forward references that lots of things need.
  */
+typedef struct brt_vdev brt_vdev_t;
 typedef struct spa spa_t;
 typedef struct vdev vdev_t;
 typedef struct metaslab metaslab_t;

include/sys/spa_impl.h

@@ -412,8 +412,12 @@ struct spa {
 	uint64_t	spa_dedup_dspace;	/* Cache get_dedup_dspace() */
 	uint64_t	spa_dedup_checksum;	/* default dedup checksum */
 	uint64_t	spa_dspace;		/* dspace in normal class */
+	uint64_t	spa_rdspace;		/* raw (non-dedup) --//-- */
 	boolean_t	spa_active_ddt_prune;	/* ddt prune process active */
-	struct brt	*spa_brt;		/* in-core BRT */
+	brt_vdev_t	**spa_brt_vdevs;	/* array of per-vdev BRTs */
+	uint64_t	spa_brt_nvdevs;		/* number of vdevs in BRT */
+	uint64_t	spa_brt_rangesize;	/* pool's BRT range size */
+	krwlock_t	spa_brt_lock;		/* Protects brt_vdevs/nvdevs */
 	kmutex_t	spa_vdev_top_lock;	/* dueling offline/remove */
 	kmutex_t	spa_proc_lock;		/* protects spa_proc* */
 	kcondvar_t	spa_proc_cv;		/* spa_proc_state transitions */