Date: Thu, 21 Mar 1996 02:44:57 -0700 (MST) From: Dave Andersen <angio@shell.aros.net> To: 103350.3250@compuserve.com (Weston Ruch) Cc: questions@freebsd.org Subject: Re: Shared Memory Question Message-ID: <199603210944.CAA03086@shell.aros.net> In-Reply-To: <960321032138_103350.3250_JHL113-1@CompuServe.COM> from Weston Ruch at "Mar 20, 96 10:21:39 pm"
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*ponder* If you're getting a segfault, something sounds wrong. The way
to change how much shared memory you can have is by putting the
options "SHMMAXPGS=XXXX" (in K blocks)
in your kernel config file.
However, the problem from that should arise when you try to allocate the
shared memory -- it should fail and return an error number to you in a
very polite fashion, not segfault.
(Unfortunatly, I haven't used enough of it to really say what *is*
happening. :)
-Dave Andersen
Lo and behold, Weston Ruch once said:
> I'm wondering if there is a problem with the shared memory implementation in
> FreeBSD 2.1.
>
> There is no problem when the shared memory segment is small. I've tested it
> extensively with 1 Kilobyte shared memory segments and everything is fine.
>
> But problems occur when I try to utilize large shared memory segments. When
> writing to the segment, the program always terminates due to an invalid memory
> reference. For example, when a 32 Kbyte segment is utilized, a SIGSEGV signal
> is encountered when writing to address 0x80b2000. When writing to a 64 Kbyte
> segment, the seg fault occurs at 0x80ba000.
>
> The system always allocates the memory at or about these address ranges and its
> no problem when shared memory segments are about 1 Kbyte. I don't quite
> understand the addresses though, since the former address corresponds to 127
> Mbytes, and the latter corresponds to 128 Mbytes and I don't have nearly that
> much memory or swap space.
>
> When I look at the core file for 32 Kbyte case in the debugger, the above
> addresses are verified, but it also states that the program had difficulty
> writing to address 0x7453203a, and I don't doubt it.
>
> I believe that either the kernel needs to be configured for more kernel memory
> (but there doesn't seem to be a parameter to do this), or perhaps there is a
> problem in the implementation.
>
> I hope I've described the situation adequately. Thanks for any info regarding
> this matter.
>
> Best Regards,
>
> Weston Ruch
>
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