SUMMARY: Kernel modification: Semaphores

From: David Gunn (ldavis!woden!gunn@snowbird.Central.Sun.COM)
Date: Thu Jul 23 1992 - 14:26:03 CDT

Hi! Sorry it took me so long to get back to you, but the problem got put
on the backburner for a while.

Here's my original request:

---------- Original message ----------
Help! I am trying to increase the number of semaphores in our kernel, but
after changing the following values in /usr/include/sys/sem.h, then running
config and making a new kernel, the new kernel and the old kernel have the
same sizes. Shouldn't the kernel size increase? And is there a limit to
the number of semaphores supported (Sun 4.1.1, SPARC2)?

Contant Old sem.h values New sem.h values
------- ---------------- ----------------
SEMMNS 60 120
SEMMNU 30 60

kernel sizes
1307282 Jun 25 17:54 /vmunix
1307282 Mar 16 10:26 /vmunix.old

---------- End of Original ----------

The general consensus was to NOT modify sem.h, but rather to add options
lines to the kernel configuration file (ie "options SEMMNS = 120").

John pointed out that "include files do not come from /usr/include/... but
from /usr/sys. In particular, /usr/sys/sys/sem.h."

John, Matthew D., Dave and Perry added that the space allocated with the SEM*
constants is allocated dynamically, not at compile time.

Guy said "SUN told me that there is no physical limit to the number of
semaphores allowed on a system. The kernel size does not change much because
it's just a 'permission' given to the system to start more semaphores."

Many thanks to all who responded:
        Howie Kaye <!howie>
        Bill Bathurst <!bathurst>
        PE-Nelson.COM!milt (Milt Ratcliff)
        John Stanley <!stanley>
        Mike Raffety <!miker>!matthew (Matthew Donaldson)
        Dave Mitchell <!D.Mitchell>!boudreau (Guy Boudreault)!matt (Matt Goheen)
        Matt Crawford <!matt>!Perry_Hutchison.Portland!grover (Dean Grover)
        sdcc10.UCSD.EDU!mce (Mark Edwards)

- David

        David Gunn Voice: (801) 375-0177
        Larson-Davis, Inc. Fax: (801) 375-0182
        Provo, UT 84604 ldavis!

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