RFC: make UMTX hash table size configurable

[Adrian Chadd]

Hi,

This patch makes the umtx hash table size configurable. It saves ~40k
of footprint from embedded images.

(I can't seem to get phabricator to create a diff based on a set of
files, rather than the whole tree. Sigh.)

adrian at lucy-11i386:~/work/freebsd/head-embedded/src % svn diff
sys/kern/ sys/conf/options
Index: sys/kern/kern_umtx.c
===================================================================
--- sys/kern/kern_umtx.c    (revision 282934)
+++ sys/kern/kern_umtx.c    (working copy)
@@ -29,7 +29,7 @@
 __FBSDID("$FreeBSD$");

 #include "opt_compat.h"
-#include "opt_umtx_profiling.h"
+#include "opt_umtx.h"

 #include <sys/param.h>
 #include <sys/kernel.h>
@@ -184,7 +184,11 @@
              PRI_MAX_TIMESHARE : (td)->td_user_pri)

 #define    GOLDEN_RATIO_PRIME    2654404609U
+#ifdef    UMTX_NUM_CHAINS
+#define    UMTX_CHAINS        UMTX_NUM_CHAINS
+#else
 #define    UMTX_CHAINS        512
+#endif    /* UMTX_NUM_CHAINS */
 #define    UMTX_SHIFTS        (__WORD_BIT - 9)

 #define    GET_SHARE(flags)    \
Index: sys/conf/options
===================================================================
--- sys/conf/options    (revision 282934)
+++ sys/conf/options    (working copy)
@@ -209,7 +209,8 @@
 SYSVSHM        opt_sysvipc.h
 SW_WATCHDOG    opt_watchdog.h
 TURNSTILE_PROFILING
-UMTX_PROFILING
+UMTX_PROFILING    opt_umtx.h
+UMTX_NUM_CHAINS    opt_umtx.h
 VFS_AIO
 VERBOSE_SYSINIT
 WLCACHE        opt_wavelan.h