From owner-freebsd-hackers  Tue Sep  5  2:43: 4 2000
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Date: Tue, 05 Sep 2000 10:30:05 +0100
From: John Toon <j.a.toon@btinternet.com>
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To: freebsd-hackers@freebsd.org
Subject: Shared Memory Issues
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Hi,

I've scoured through the net and the mailing archives, but was unable to
find any satisfactory information on a certain problem I'm suffering at
the moment.

After getting the dreaded "shmget() failed" error message, I have since
tried several recompiles of the kernel to fix the problem.

I added 

options SHMMAXPGS=16385
options SHMMAX=(SHMMAXPGS*PAGE_SIZE+1)

to my new kernel and recompiled.

However, under XFree86 4.0, I still seem to be getting shared memory
issues.

Compupic refuses to start under GNOME issuing

X Error of failed request:  BadAccess (attempt to access private
resource denied)
  Major opcode of failed request:  146 (MIT-SHM)
  Minor opcode of failed request:  1 (X_ShmAttach)
  Serial number of failed request:  2961
  Current serial number in output stream:  2962

Yet works under VTWM - until I load up a few applications, when it
terminates again, with the same problem. More annoyingly, FXTV also dies
with the same problem. 

Next, I tried another kernel, this time with the following options:

options         SEMMNI=100
options         SEMMNS=300
options         SEMUME=100
options         SEMMNU=150
options         SHMMAXPGS=16385

I omitted the SHMMAX option, as I have read that this option is now
deprecated. Unfortunately, this kernel was not better.

I'm currently running FreeBSD 4.0-RELEASE.

Several questions;

1. If I upgrade to 4.1-STABLE (which I will be soon), will the shared
memory issue disappear?
2. I am not sure as to the exact options (and combination of options I
should be choosing). My computer has 384MB of RAM - I want to be able to
make *optimum* use of all that memory, and run X sessions with heavy
loads - can someone suggest the particular values I should be using?
3. ...and of course, how do I fix this? With the amount of RAM I've got,
getting memory issues is silly, so I would like to resolve this.

Finally, can anyone recommend any books/URLs on the SYSV shared memory
management? I'm curious to know more about the way different
applications utilize memory; most applications run perfectly; the GIMP
loads up in about 1 second.

Thanks,

John.



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