RFC: make UMTX hash table size configurable

[Eric van Gyzen]

Adrian,

Good idea.  Looks good to me.

Eric

On 05/20/2015 12:28, Adrian Chadd wrote:
> 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
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