Shared memory not enabled in 2.4.0?

For some reason shared memory is not being enabled on my system running kernel v2.4.0 (on RedHat v6.2, with all updates applied).

Per the documentation I have this line in my /etc/fstab:

none /dev/shm shm defaults 0 0

Yes, I have created this subdirectory:

     # ls -l /dev | grep shm
     drwxrwxrwt    1 root     root            0 Jan  7 11:54 shm

No complaints are seen at startup, yet I still have no shared memory:

     # cat /proc/meminfo
             total:    used:    free:  shared: buffers:  cached:
     Mem:  130293760 123133952  7159808        0 30371840 15179776
     Swap: 136241152        0 136241152
     MemTotal:       127240 kB
     MemFree:          6992 kB
     MemShared:           0 kB
     Buffers:         29660 kB
     Cached:          14824 kB
     Active:           3400 kB
     Inact_dirty:     37872 kB
     Inact_clean:      3212 kB
     Inact_target:        4 kB
     HighTotal:           0 kB
     HighFree:            0 kB
     LowTotal:       127240 kB
     LowFree:          6992 kB
     SwapTotal:      133048 kB
     SwapFree:       133048 kB

Is there some configuration option which I missed? Some trick not mentioned in the doc?

Thank you.

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[Snipped...]

You do have shared memory or else your shared libraries would not work. The problem is that somebody decided that the CPU cost to calculate the amount used was "too great", so it's not being shown.

Hopefully this will be resolved at a later date and we will again be able to see shared memory activity.

Cheers,
Dick Johnson

Penguin : Linux version 2.4.0 on an i686 machine (799.54 BogoMips).

"Memory is like gasoline. You use it up when you are running. Of course you get it all back when you reboot..."; Actual explanation obtained from the Micro$oft help desk.

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This is not SysV/POSIX shared memory. This used to mean the memory that was shared between processes (from librares etc.). It became too expensive to calculate so it was removed. It only remains in /proc/meminfo for backwards compatability with programs that parse that file.

--

Brian Gerst
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On Mon, Jan 08, 2001 at 01:11:19PM -0600, [email protected] wrote:
[snip]

[snip]

The shared field is currently unused in 2.4.
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Try 'ipcs' and you'll see your shared mem segments info...

J.A. Magallon                                                      $> cd pub
mailto:[email protected]                                          $> more beer

Linux werewolf 2.4.0-ac3 #2 SMP Sun Jan 7 02:13:37 CET 2001 i686

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You should check shared memory with "ipcs" instead.

Make sure you enabled "System V IPC" under "General Setup" (it's a default value, though).

Ernesto Hernández-Novich - Running Linux 2.4.0 i686 - Unix: Live free or die!
-----BEGIN GEEK CODE BLOCK-----
Version: 3.1
GCS/E d+(++) s+: a C+++$ UBLAVHIOSC*++++$ P++++$ L+++$ E- W+ N++ o K++ w--- O-
M- V PS+ PE Y+ PGP>++ t+ 5 X+ R* tv+ b++ DI+++$ D++ G++ e++ h r++ y+
-----END GEEK CODE BLOCK-----


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You are confusing System V shared memory (IPC) with VM shared memory. The
'0' for shared in /proc/meminfo means the system can't easily tell you how much memory the VM is sharing. But this has nothing whatsoever to do with IPC shared memory, which is what the /dev/shm thing is about.

DS

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                                         ^^^^^^^^^^

It means shared process memory, not shm.

One thing to watch : PowerTweak. Seems to set the max shm segments to 0

Igmar

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