Add TRIM support

UNMAP/TRIM support is a frequently-requested feature to help
prevent performance from degrading on SSDs and on various other
SAN-like storage back-ends.  By issuing UNMAP/TRIM commands for
sectors which are no longer allocated the underlying device can
often more efficiently manage itself.

This TRIM implementation is modeled on the `zpool initialize`
feature which writes a pattern to all unallocated space in the
pool.  The new `zpool trim` command uses the same vdev_xlate()
code to calculate what sectors are unallocated, the same per-
vdev TRIM thread model and locking, and the same basic CLI for
a consistent user experience.  The core difference is that
instead of writing a pattern it will issue UNMAP/TRIM commands
for those extents.

The zio pipeline was updated to accommodate this by adding a new
ZIO_TYPE_TRIM type and associated spa taskq.  This new type makes
is straight forward to add the platform specific TRIM/UNMAP calls
to vdev_disk.c and vdev_file.c.  These new ZIO_TYPE_TRIM zios are
handled largely the same way as ZIO_TYPE_READs or ZIO_TYPE_WRITEs.
This makes it possible to largely avoid changing the pipieline,
one exception is that TRIM zio's may exceed the 16M block size
limit since they contain no data.

In addition to the manual `zpool trim` command, a background
automatic TRIM was added and is controlled by the 'autotrim'
property.  It relies on the exact same infrastructure as the
manual TRIM.  However, instead of relying on the extents in a
metaslab's ms_allocatable range tree, a ms_trim tree is kept
per metaslab.  When 'autotrim=on', ranges added back to the
ms_allocatable tree are also added to the ms_free tree.  The
ms_free tree is then periodically consumed by an autotrim
thread which systematically walks a top level vdev's metaslabs.

Since the automatic TRIM will skip ranges it considers too small
there is value in occasionally running a full `zpool trim`.  This
may occur when the freed blocks are small and not enough time
was allowed to aggregate them.  An automatic TRIM and a manual
`zpool trim` may be run concurrently, in which case the automatic
TRIM will yield to the manual TRIM.

Reviewed-by: Jorgen Lundman <[email protected]>
Reviewed-by: Tim Chase <[email protected]>
Reviewed-by: Matt Ahrens <[email protected]>
Reviewed-by: George Wilson <[email protected]>
Reviewed-by: Serapheim Dimitropoulos <[email protected]>
Contributions-by: Saso Kiselkov <[email protected]>
Contributions-by: Tim Chase <[email protected]>
Contributions-by: Chunwei Chen <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #8419 
Closes #598 

1 files changed, 128 insertions, 13 deletions

diff --git a/module/zfs/metaslab.c b/module/zfs/metaslab.c
index 8380897a9..06d8383f0 100644
--- a/module/zfs/metaslab.c
+++ b/module/zfs/metaslab.c
@@ -181,7 +181,6 @@ int metaslab_lba_weighting_enabled = B_TRUE;
  */
 int metaslab_bias_enabled = B_TRUE;
 
-
 /*
  * Enable/disable remapping of indirect DVAs to their concrete vdevs.
  */
@@ -219,6 +218,12 @@ boolean_t metaslab_trace_enabled = B_TRUE;
 uint64_t metaslab_trace_max_entries = 5000;
 #endif
 
+/*
+ * Maximum number of metaslabs per group that can be disabled
+ * simultaneously.
+ */
+int max_disabled_ms = 3;
+
 static uint64_t metaslab_weight(metaslab_t *);
 static void metaslab_set_fragmentation(metaslab_t *);
 static void metaslab_free_impl(vdev_t *, uint64_t, uint64_t, boolean_t);
@@ -652,8 +657,8 @@ metaslab_group_create(metaslab_class_t *mc, vdev_t *vd, int allocators)
 
 	mg = kmem_zalloc(sizeof (metaslab_group_t), KM_SLEEP);
 	mutex_init(&mg->mg_lock, NULL, MUTEX_DEFAULT, NULL);
-	mutex_init(&mg->mg_ms_initialize_lock, NULL, MUTEX_DEFAULT, NULL);
-	cv_init(&mg->mg_ms_initialize_cv, NULL, CV_DEFAULT, NULL);
+	mutex_init(&mg->mg_ms_disabled_lock, NULL, MUTEX_DEFAULT, NULL);
+	cv_init(&mg->mg_ms_disabled_cv, NULL, CV_DEFAULT, NULL);
 	mg->mg_primaries = kmem_zalloc(allocators * sizeof (metaslab_t *),
 	    KM_SLEEP);
 	mg->mg_secondaries = kmem_zalloc(allocators * sizeof (metaslab_t *),
@@ -700,8 +705,8 @@ metaslab_group_destroy(metaslab_group_t *mg)
 	kmem_free(mg->mg_secondaries, mg->mg_allocators *
 	    sizeof (metaslab_t *));
 	mutex_destroy(&mg->mg_lock);
-	mutex_destroy(&mg->mg_ms_initialize_lock);
-	cv_destroy(&mg->mg_ms_initialize_cv);
+	mutex_destroy(&mg->mg_ms_disabled_lock);
+	cv_destroy(&mg->mg_ms_disabled_cv);
 
 	for (int i = 0; i < mg->mg_allocators; i++) {
 		zfs_refcount_destroy(&mg->mg_alloc_queue_depth[i]);
@@ -1846,8 +1851,10 @@ metaslab_init(metaslab_group_t *mg, uint64_t id, uint64_t object, uint64_t txg,
 	 */
 	ms->ms_allocatable = range_tree_create_impl(&rt_avl_ops,
 	    &ms->ms_allocatable_by_size, metaslab_rangesize_compare, 0);
-	metaslab_group_add(mg, ms);
 
+	ms->ms_trim = range_tree_create(NULL, NULL);
+
+	metaslab_group_add(mg, ms);
 	metaslab_set_fragmentation(ms);
 
 	/*
@@ -1921,6 +1928,9 @@ metaslab_fini(metaslab_t *msp)
 	for (int t = 0; t < TXG_SIZE; t++)
 		ASSERT(!txg_list_member(&vd->vdev_ms_list, msp, t));
 
+	range_tree_vacate(msp->ms_trim, NULL, NULL);
+	range_tree_destroy(msp->ms_trim);
+
 	mutex_exit(&msp->ms_lock);
 	cv_destroy(&msp->ms_load_cv);
 	mutex_destroy(&msp->ms_lock);
@@ -2727,6 +2737,7 @@ metaslab_sync(metaslab_t *msp, uint64_t txg)
 	ASSERT3P(msp->ms_freeing, !=, NULL);
 	ASSERT3P(msp->ms_freed, !=, NULL);
 	ASSERT3P(msp->ms_checkpointing, !=, NULL);
+	ASSERT3P(msp->ms_trim, !=, NULL);
 
 	/*
 	 * Normally, we don't want to process a metaslab if there are no
@@ -3000,6 +3011,24 @@ metaslab_sync_done(metaslab_t *msp, uint64_t txg)
 	metaslab_load_wait(msp);
 
 	/*
+	 * When auto-trimming is enabled, free ranges which are added to
+	 * ms_allocatable are also be added to ms_trim.  The ms_trim tree is
+	 * periodically consumed by the vdev_autotrim_thread() which issues
+	 * trims for all ranges and then vacates the tree.  The ms_trim tree
+	 * can be discarded at any time with the sole consequence of recent
+	 * frees not being trimmed.
+	 */
+	if (spa_get_autotrim(spa) == SPA_AUTOTRIM_ON) {
+		range_tree_walk(*defer_tree, range_tree_add, msp->ms_trim);
+		if (!defer_allowed) {
+			range_tree_walk(msp->ms_freed, range_tree_add,
+			    msp->ms_trim);
+		}
+	} else {
+		range_tree_vacate(msp->ms_trim, NULL, NULL);
+	}
+
+	/*
 	 * Move the frees from the defer_tree back to the free
 	 * range tree (if it's loaded). Swap the freed_tree and
 	 * the defer_tree -- this is safe to do because we've
@@ -3047,7 +3076,7 @@ metaslab_sync_done(metaslab_t *msp, uint64_t txg)
 	 * from it in 'metaslab_unload_delay' txgs, then unload it.
 	 */
 	if (msp->ms_loaded &&
-	    msp->ms_initializing == 0 &&
+	    msp->ms_disabled == 0 &&
 	    msp->ms_selected_txg + metaslab_unload_delay < txg) {
 
 		for (int t = 1; t < TXG_CONCURRENT_STATES; t++) {
@@ -3330,7 +3359,7 @@ metaslab_block_alloc(metaslab_t *msp, uint64_t size, uint64_t txg)
 	metaslab_class_t *mc = msp->ms_group->mg_class;
 
 	VERIFY(!msp->ms_condensing);
-	VERIFY0(msp->ms_initializing);
+	VERIFY0(msp->ms_disabled);
 
 	start = mc->mc_ops->msop_alloc(msp, size);
 	if (start != -1ULL) {
@@ -3341,6 +3370,7 @@ metaslab_block_alloc(metaslab_t *msp, uint64_t size, uint64_t txg)
 		VERIFY0(P2PHASE(size, 1ULL << vd->vdev_ashift));
 		VERIFY3U(range_tree_space(rt) - size, <=, msp->ms_size);
 		range_tree_remove(rt, start, size);
+		range_tree_clear(msp->ms_trim, start, size);
 
 		if (range_tree_is_empty(msp->ms_allocating[txg & TXG_MASK]))
 			vdev_dirty(mg->mg_vd, VDD_METASLAB, msp, txg);
@@ -3391,10 +3421,10 @@ find_valid_metaslab(metaslab_group_t *mg, uint64_t activation_weight,
 		}
 
 		/*
-		 * If the selected metaslab is condensing or being
-		 * initialized, skip it.
+		 * If the selected metaslab is condensing or disabled,
+		 * skip it.
 		 */
-		if (msp->ms_condensing || msp->ms_initializing > 0)
+		if (msp->ms_condensing || msp->ms_disabled > 0)
 			continue;
 
 		*was_active = msp->ms_allocator != -1;
@@ -3566,9 +3596,9 @@ metaslab_group_alloc_normal(metaslab_group_t *mg, zio_alloc_list_t *zal,
 			    ~METASLAB_ACTIVE_MASK);
 			mutex_exit(&msp->ms_lock);
 			continue;
-		} else if (msp->ms_initializing > 0) {
+		} else if (msp->ms_disabled > 0) {
 			metaslab_trace_add(zal, mg, msp, asize, d,
-			    TRACE_INITIALIZING, allocator);
+			    TRACE_DISABLED, allocator);
 			metaslab_passivate(msp, msp->ms_weight &
 			    ~METASLAB_ACTIVE_MASK);
 			mutex_exit(&msp->ms_lock);
@@ -4294,6 +4324,7 @@ metaslab_claim_concrete(vdev_t *vd, uint64_t offset, uint64_t size,
 	VERIFY3U(range_tree_space(msp->ms_allocatable) - size, <=,
 	    msp->ms_size);
 	range_tree_remove(msp->ms_allocatable, offset, size);
+	range_tree_clear(msp->ms_trim, offset, size);
 
 	if (spa_writeable(spa)) {	/* don't dirty if we're zdb(1M) */
 		if (range_tree_is_empty(msp->ms_allocating[txg & TXG_MASK]))
@@ -4606,6 +4637,7 @@ metaslab_check_free_impl(vdev_t *vd, uint64_t offset, uint64_t size)
 		    offset, size);
 	}
 
+	range_tree_verify_not_present(msp->ms_trim, offset, size);
 	range_tree_verify_not_present(msp->ms_freeing, offset, size);
 	range_tree_verify_not_present(msp->ms_checkpointing, offset, size);
 	range_tree_verify_not_present(msp->ms_freed, offset, size);
@@ -4637,6 +4669,89 @@ metaslab_check_free(spa_t *spa, const blkptr_t *bp)
 	spa_config_exit(spa, SCL_VDEV, FTAG);
 }
 
+static void
+metaslab_group_disable_wait(metaslab_group_t *mg)
+{
+	ASSERT(MUTEX_HELD(&mg->mg_ms_disabled_lock));
+	while (mg->mg_disabled_updating) {
+		cv_wait(&mg->mg_ms_disabled_cv, &mg->mg_ms_disabled_lock);
+	}
+}
+
+static void
+metaslab_group_disabled_increment(metaslab_group_t *mg)
+{
+	ASSERT(MUTEX_HELD(&mg->mg_ms_disabled_lock));
+	ASSERT(mg->mg_disabled_updating);
+
+	while (mg->mg_ms_disabled >= max_disabled_ms) {
+		cv_wait(&mg->mg_ms_disabled_cv, &mg->mg_ms_disabled_lock);
+	}
+	mg->mg_ms_disabled++;
+	ASSERT3U(mg->mg_ms_disabled, <=, max_disabled_ms);
+}
+
+/*
+ * Mark the metaslab as disabled to prevent any allocations on this metaslab.
+ * We must also track how many metaslabs are currently disabled within a
+ * metaslab group and limit them to prevent allocation failures from
+ * occurring because all metaslabs are disabled.
+ */
+void
+metaslab_disable(metaslab_t *msp)
+{
+	ASSERT(!MUTEX_HELD(&msp->ms_lock));
+	metaslab_group_t *mg = msp->ms_group;
+
+	mutex_enter(&mg->mg_ms_disabled_lock);
+
+	/*
+	 * To keep an accurate count of how many threads have disabled
+	 * a specific metaslab group, we only allow one thread to mark
+	 * the metaslab group at a time. This ensures that the value of
+	 * ms_disabled will be accurate when we decide to mark a metaslab
+	 * group as disabled. To do this we force all other threads
+	 * to wait till the metaslab's mg_disabled_updating flag is no
+	 * longer set.
+	 */
+	metaslab_group_disable_wait(mg);
+	mg->mg_disabled_updating = B_TRUE;
+	if (msp->ms_disabled == 0) {
+		metaslab_group_disabled_increment(mg);
+	}
+	mutex_enter(&msp->ms_lock);
+	msp->ms_disabled++;
+	mutex_exit(&msp->ms_lock);
+
+	mg->mg_disabled_updating = B_FALSE;
+	cv_broadcast(&mg->mg_ms_disabled_cv);
+	mutex_exit(&mg->mg_ms_disabled_lock);
+}
+
+void
+metaslab_enable(metaslab_t *msp, boolean_t sync)
+{
+	metaslab_group_t *mg = msp->ms_group;
+	spa_t *spa = mg->mg_vd->vdev_spa;
+
+	/*
+	 * Wait for the outstanding IO to be synced to prevent newly
+	 * allocated blocks from being overwritten.  This used by
+	 * initialize and TRIM which are modifying unallocated space.
+	 */
+	if (sync)
+		txg_wait_synced(spa_get_dsl(spa), 0);
+
+	mutex_enter(&mg->mg_ms_disabled_lock);
+	mutex_enter(&msp->ms_lock);
+	if (--msp->ms_disabled == 0) {
+		mg->mg_ms_disabled--;
+		cv_broadcast(&mg->mg_ms_disabled_cv);
+	}
+	mutex_exit(&msp->ms_lock);
+	mutex_exit(&mg->mg_ms_disabled_lock);
+}
+
 #if defined(_KERNEL)
 /* BEGIN CSTYLED */
 module_param(metaslab_aliquot, ulong, 0644);