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From: df@phx.mcd.mot.com (Dale Farnsworth)
Newsgroups: comp.unix.wizards
Subject: Re: shared memory
Message-ID: <12158@mcdphx.phx.mcd.mot.com>
Date: 13 Dec 89 23:59:00 GMT
References: <11383@csli.Stanford.EDU> <1989Dec12.005555.20618@virtech.uucp> <21223@mimsy.umd.edu>
Sender: listen@mcdphx.phx.mcd.mot.com
Reply-To: df@phx.mcd.mot.com (Dale Farnsworth)
Organization: Motorola Microcomputer Division, Tempe, Az.
Lines: 19

Chris Torek (chris@mimsy.umd.edu) writes:
> 
> As I understand it---which is not to say that it is so, for I have
> never seen the SysRel% 1, 2, or 3# code itself---the total amount of
> shared memory allowed per-system is reserved at boot time, is not
> pageable, and is effectively taken away from the rest of the system.
> For processes not using it, it is as if some of the machine's memory
> had been physically removed.
> 
> This would mitigate against raising SHMMAX arbitrarily....

I'm glad you started with a disclaimer.  I've seen several System V shared
memory implementations, and *none* of them reserve shared memory at boot
time.  If the system supports paging, the shared memory is paged as well.

-Dale

-- 
Dale Farnsworth