zfs: is it possible to set metaslab_debug to 1?

[Tom]

Hi,

Is it possible to set metaslab_debug to 1 on freebsd without recompiling:
usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/metaslab.c

/*
 * Metaslab debugging: when set, keeps all space maps in core to verify
frees.
 */
static int metaslab_debug = 0;

Is this even possible on FreeBSD? It often helps with ZFS perfomance
issues on Solaris with lots of ram.

Regards,
Tom