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Old 08-31-2005, 07:41 PM   #1
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ipcs -lm shows : max total shared memory (kbytes) = 0

when I am running the ipcs command I have the output:

ipcs -lm

------ Shared Memory Limits --------
max number of segments = 4096
max seg size (kbytes) = 1048576
max total shared memory (kbytes) = 0
min seg size (bytes) = 1

what can be done to change the max total shared memory (kbytes) = 0 from 0 to anything?



cat /proc/sys/kernel/shmmax

ipcs -a

------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x0052e2c1 0 postgres 600 18735104 14
0x00000000 4620289 root 600 46084 14 dest
0x00000002 131074 root 600 196608 2
0x00000003 163843 root 600 655360 2
0x00000000 5668868 gdm 777 196608 2 dest
0x00000000 5734405 gdm 777 196608 2 dest

------ Semaphore Arrays --------
key semid owner perms nsems status
0x0052e2c1 0 postgres 600 17
0x0052e2c2 32769 postgres 600 17
0x0052e2c3 65538 postgres 600 17
0x0052e2c4 98307 postgres 600 17
0x0052e2c5 131076 postgres 600 17
0x0052e2c6 163845 postgres 600 17
0x0052e2c7 196614 postgres 600 17
0x00000000 294919 helpdesk 600 1
0x00000200 262152 wire 666 1

------ Message Queues --------
key msqid owner perms used-bytes messages

ipcs -u

------ Shared Memory Status --------
segments allocated 6
pages allocated 4890
pages resident 4134
pages swapped 125
Swap performance: 0 attempts 0 successes

------ Semaphore Status --------
used arrays = 9
allocated semaphores = 121

------ Messages: Status --------
allocated queues = 0
used headers = 0
used space = 0 bytes

What is wrong?
Old 09-01-2005, 11:58 AM   #2
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Odd - if it is really 0 then I wouldn't have thought ipcs -u would have shown any shared memory segments.

The parameter that sets this is SHMALL as I just found out from my reading. This is the global shared memory allowed whereas SHMMAX is the shared memory allowed per segment.

It isn't unsual that setting a parameter to 0 means "unlimited" rather than 0. The fact that you DO have shared memory segments suggests to me that this is the case for SHMALL. If so there is no need to change it. Unfortunately in my breif search I didn't find anything to confirm this.

Also if the above is the case then your limit would of course be physical memory (actually somewhat less because memory is used for other things that don't show up in shared memory). You might want to see what "free" tells you about memory usage.
See if the total of the size listed for segments in use is. It may simply be that you are out of memory so can't allocate any more segments.

What I did note was that your postgress segment has 0 on it. Are you having an issue with postgress? If so it may be what you need to do is figure out how to tell postgress to grab a larger memory segment. Also it may just be it couldn't get any memory as discussed in the prior paragraph.


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