Add metaslab_debug option

Enabling metaslab debugging will prevent space maps from being
automatically unloaded.  This can significantly increase the
memory footprint but being able to dynamically control this is
helpful for debugging and certain performance testing.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

diff --git a/module/zfs/metaslab.c b/module/zfs/metaslab.c
index d199921b7edf1a17d6bc7ab2c20275941a340d91..03d5a1d9c75ee865a907ba8d5ac3d6b2a86b9a22 100644 (file)
--- a/module/zfs/metaslab.c
+++ b/module/zfs/metaslab.c
@@ -58,7 +58,7 @@ int zfs_mg_alloc_failures;
 /*
  * Metaslab debugging: when set, keeps all space maps in core to verify frees.
  */
-static int metaslab_debug = 0;
+int metaslab_debug = 0;
 
 /*
  * Minimum size which forces the dynamic allocator to change
@@ -1746,3 +1746,8 @@ void metaslab_fastwrite_unmark(spa_t *spa, const blkptr_t *bp)
 
        spa_config_exit(spa, SCL_VDEV, FTAG);
 }
+
+#if defined(_KERNEL) && defined(HAVE_SPL)
+module_param(metaslab_debug, int, 0644);
+MODULE_PARM_DESC(metaslab_debug, "keep space maps in core to verify frees");
+#endif /* _KERNEL && HAVE_SPL */