metaslab: expose condense_pct and sm_blksz tunables on Linux

Expose zfs_metaslab_condense_pct and zfs_metaslab_sm_blksz_* as
module parameters on Linux, matching their existing FreeBSD sysctls.

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Alexander Motin <[email protected]>
Signed-off-by: Christos Longros <[email protected]>
Closes #18594

include/sys/metaslab_impl.h

@@ -330,7 +330,7 @@ struct metaslab_group {
  *
  * As the space map grows (as a result of the appends) it will
  * eventually become space-inefficient.  When the metaslab's in-core
- * free tree is zfs_condense_pct/100 times the size of the minimal
+ * free tree is zfs_metaslab_condense_pct/100 times the size of the minimal
  * on-disk representation, we rewrite it in its minimized form.  If a
  * metaslab needs to condense then we must set the ms_condensing flag to
  * ensure that allocations are not performed on the metaslab that is

man/man4/zfs.4

@@ -446,6 +446,32 @@ This improves performance, especially when there are many metaslabs per vdev
 and the allocation can't actually be satisfied
 (so we would otherwise iterate all metaslabs).
 .
+.It Sy zfs_metaslab_sm_blksz_no_log Ns = Ns Sy 16384 Ns B Po 16 KiB Pc Pq int
+Block size for the metaslab space maps in pools where the
+.Sy log_spacemap
+feature is disabled.
+Multiple metaslabs are modified per transaction group, so a smaller block size
+lets more, scattered I/O operations be issued.
+Must be a power of 2 greater than
+.Sy 4096 .
+This parameter can only be set at module load time.
+.
+.It Sy zfs_metaslab_sm_blksz_with_log Ns = Ns Sy 131072 Ns B Po 128 KiB Pc Pq int
+Block size for the metaslab space maps in pools where the
+.Sy log_spacemap
+feature is enabled.
+Changes are batched in the per-pool log spacemap and flushed to each metaslab's
+space map only occasionally, so a larger block size is more efficient.
+Must be a power of 2 greater than
+.Sy 4096 .
+This parameter can only be set at module load time.
+.
+.It Sy zfs_metaslab_condense_pct Ns = Ns Sy 200 Ns % Pq uint
+Condense an on-disk space map when its size exceeds this percentage of
+the in-memory representation.
+The minimum is
+.Sy 100 .
+.
 .It Sy zfs_vdev_default_ms_count Ns = Ns Sy 200 Pq uint
 When a vdev is added, target this number of metaslabs per top-level vdev.
 .

module/os/freebsd/zfs/sysctl_os.c

@@ -289,46 +289,6 @@ param_set_active_allocator(SYSCTL_HANDLER_ARGS)
 	return (param_set_active_allocator_common(buf));
 }
 
-/*
- * In pools where the log space map feature is not enabled we touch
- * multiple metaslabs (and their respective space maps) with each
- * transaction group. Thus, we benefit from having a small space map
- * block size since it allows us to issue more I/O operations scattered
- * around the disk. So a sane default for the space map block size
- * is 8~16K.
- */
-extern int zfs_metaslab_sm_blksz_no_log;
-
-SYSCTL_INT(_vfs_zfs_metaslab, OID_AUTO, sm_blksz_no_log,
-	CTLFLAG_RDTUN, &zfs_metaslab_sm_blksz_no_log, 0,
-	"Block size for space map in pools with log space map disabled.  "
-	"Power of 2 greater than 4096.");
-
-/*
- * When the log space map feature is enabled, we accumulate a lot of
- * changes per metaslab that are flushed once in a while so we benefit
- * from a bigger block size like 128K for the metaslab space maps.
- */
-extern int zfs_metaslab_sm_blksz_with_log;
-
-SYSCTL_INT(_vfs_zfs_metaslab, OID_AUTO, sm_blksz_with_log,
-	CTLFLAG_RDTUN, &zfs_metaslab_sm_blksz_with_log, 0,
-	"Block size for space map in pools with log space map enabled.  "
-	"Power of 2 greater than 4096.");
-
-/*
- * The in-core space map representation is more compact than its on-disk form.
- * The zfs_condense_pct determines how much more compact the in-core
- * space map representation must be before we compact it on-disk.
- * Values should be greater than or equal to 100.
- */
-extern uint_t zfs_condense_pct;
-
-SYSCTL_UINT(_vfs_zfs, OID_AUTO, condense_pct,
-	CTLFLAG_RWTUN, &zfs_condense_pct, 0,
-	"Condense on-disk spacemap when it is more than this many percents"
-	" of in-memory counterpart");
-
 /*
  * Minimum size which forces the dynamic allocator to change
  * it's allocation strategy.  Once the space map cannot satisfy

module/zfs/metaslab.c

@@ -82,11 +82,11 @@ int zfs_metaslab_sm_blksz_with_log = (1 << 17);
 
 /*
  * The in-core space map representation is more compact than its on-disk form.
- * The zfs_condense_pct determines how much more compact the in-core
+ * The zfs_metaslab_condense_pct determines how much more compact the in-core
  * space map representation must be before we compact it on-disk.
  * Values should be greater than or equal to 100.
  */
-uint_t zfs_condense_pct = 200;
+uint_t zfs_metaslab_condense_pct = 200;
 
 /*
  * Condensing a metaslab is not guaranteed to actually reduce the amount of
@@ -3826,8 +3826,8 @@ metaslab_group_preload(metaslab_group_t *mg)
  *    increase as a result of writing out the free space range tree.
  *
  * 2. Condense if the on on-disk space map representation is at least
- *    zfs_condense_pct/100 times the size of the optimal representation
- *    (i.e. zfs_condense_pct = 110 and in-core = 1MB, optimal = 1.1MB).
+ *    zfs_metaslab_condense_pct/100 times the size of the optimal representation
+ *    (i.e. zfs_metaslab_condense_pct = 110 and in-core = 1MB, optimal = 1.1MB).
  *
  * 3. Do not condense if the on-disk size of the space map does not actually
  *    decrease.
@@ -3863,7 +3863,8 @@ metaslab_should_condense(metaslab_t *msp)
 	uint64_t optimal_size = space_map_estimate_optimal_size(sm,
 	    msp->ms_allocatable, SM_NO_VDEVID);
 
-	return (object_size >= (optimal_size * zfs_condense_pct / 100) &&
+	return (object_size >=
+	    (optimal_size * zfs_metaslab_condense_pct / 100) &&
 	    object_size > zfs_metaslab_condense_block_threshold * record_size);
 }
 
@@ -6454,6 +6455,18 @@ ZFS_MODULE_PARAM(zfs_metaslab, zfs_metaslab_, try_hard_before_gang, INT,
 ZFS_MODULE_PARAM(zfs_metaslab, zfs_metaslab_, find_max_tries, UINT, ZMOD_RW,
 	"Normally only consider this many of the best metaslabs in each vdev");
 
+ZFS_MODULE_PARAM(zfs_metaslab, zfs_metaslab_, sm_blksz_no_log, INT, ZMOD_RW,
+	"Block size for space map in pools with log space map disabled.  "
+	"Power of 2 greater than 4096.");
+
+ZFS_MODULE_PARAM(zfs_metaslab, zfs_metaslab_, sm_blksz_with_log, INT, ZMOD_RW,
+	"Block size for space map in pools with log space map enabled.  "
+	"Power of 2 greater than 4096.");
+
 ZFS_MODULE_PARAM_CALL(zfs, zfs_, active_allocator,
 	param_set_active_allocator, param_get_charp, ZMOD_RW,
 	"SPA active allocator");
+
+ZFS_MODULE_PARAM(zfs_metaslab, zfs_metaslab_, condense_pct, UINT, ZMOD_RW,
+	"Condense on-disk spacemap when it is more than this many percents "
+	"of in-memory counterpart");