metaslab: expose df_alloc_threshold and df_free_pct on Linux

Expose metaslab_df_alloc_threshold and metaslab_df_free_pct as module
parameters on Linux, matching their existing FreeBSD sysctls.

Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Christos Longros <chris.longros@gmail.com>
Closes #18632

man/man4/zfs.4

@@ -390,6 +390,18 @@ this is
 or
 .Em 2*1024 Pq with Sy ashift Ns = Ns Sy 12 .
 .
+.It Sy metaslab_df_alloc_threshold Ns = Ns Sy 131072 Ns B Po 128 KiB Pc Pq u64
+Minimum size which forces the dynamic allocator to change its allocation
+strategy.
+Once the space map cannot satisfy an allocation of this size, it switches to a
+more aggressive strategy (searching by size rather than offset).
+.
+.It Sy metaslab_df_free_pct Ns = Ns Sy 4 Ns % Pq uint
+The minimum free space, in percent, which must be available in a space map to
+continue allocations in a first-fit fashion.
+Once free space drops below this level, allocations switch to a best-fit
+strategy.
+.
 .It Sy metaslab_df_use_largest_segment Ns = Ns Sy 0 Ns | Ns 1 Pq int
 If not searching forward (due to
 .Sy metaslab_df_max_search , metaslab_df_free_pct ,

module/os/freebsd/zfs/sysctl_os.c

@@ -289,32 +289,6 @@ param_set_active_allocator(SYSCTL_HANDLER_ARGS)
 	return (param_set_active_allocator_common(buf));
 }
 
-/*
- * Minimum size which forces the dynamic allocator to change
- * it's allocation strategy.  Once the space map cannot satisfy
- * an allocation of this size then it switches to using more
- * aggressive strategy (i.e search by size rather than offset).
- */
-extern uint64_t metaslab_df_alloc_threshold;
-
-SYSCTL_QUAD(_vfs_zfs_metaslab, OID_AUTO, df_alloc_threshold,
-	CTLFLAG_RWTUN, &metaslab_df_alloc_threshold, 0,
-	"Minimum size which forces the dynamic allocator to change its"
-	" allocation strategy");
-
-/*
- * The minimum free space, in percent, which must be available
- * in a space map to continue allocations in a first-fit fashion.
- * Once the space map's free space drops below this level we dynamically
- * switch to using best-fit allocations.
- */
-extern uint_t metaslab_df_free_pct;
-
-SYSCTL_UINT(_vfs_zfs_metaslab, OID_AUTO, df_free_pct,
-	CTLFLAG_RWTUN, &metaslab_df_free_pct, 0,
-	"The minimum free space, in percent, which must be available in a"
-	" space map to continue allocations in a first-fit fashion");
-
 /* mmp.c */
 
 int

module/zfs/metaslab.c

@@ -6443,6 +6443,14 @@ ZFS_MODULE_PARAM(zfs_metaslab, metaslab_, df_max_search, UINT, ZMOD_RW,
 ZFS_MODULE_PARAM(zfs_metaslab, metaslab_, df_use_largest_segment, INT, ZMOD_RW,
 	"When looking in size tree, use largest segment instead of exact fit");
 
+ZFS_MODULE_PARAM(zfs_metaslab, metaslab_, df_alloc_threshold, U64, ZMOD_RW,
+	"Minimum size which forces the dynamic allocator to change its "
+	"allocation strategy");
+
+ZFS_MODULE_PARAM(zfs_metaslab, metaslab_, df_free_pct, UINT, ZMOD_RW,
+	"The minimum free space, in percent, to continue allocations in a "
+	"first-fit fashion");
+
 ZFS_MODULE_PARAM(zfs_metaslab, zfs_metaslab_, max_size_cache_sec, U64,
 	ZMOD_RW, "How long to trust the cached max chunk size of a metaslab");