How to find Shared Memory Limits and Semaphore Limits in Solaris,HP-UX and AIX?

Question

I'm using the following commands to find Shared Memory Limits and Semaphore Limits in Linux.

To find Shared Memory Limits I used this command:

ipcs -lm

and I got the following output:

------ Shared Memory Limits --------
max number of segments = 4096
max seg size (kbytes) = 4194303
max total shared memory (kbytes) = 1073741824
min seg size (bytes) = 1

To find Semaphore Limits I used this command:

ipcs -ls

and I got the following output:

------ Semaphore Limits --------
max number of arrays = 128
max semaphores per array = 250
max semaphores system wide = 32000
max ops per semop call = 32
semaphore max value = 32767

I don't know how to get this output in Solaris,HP-UX and AIX. I have searched lot in internet but I couldn't get the fine solution. Share your ideas to get this thanks in advance.

Solution

Trial and error

The simplest and more robust method is to probe if you can allocate these resources, i.e.:

int shmid = shmget(key, LARGE_BUFFER_SIZE, 0644 | IPC_CREAT);
void* data = shmat(shmid, NULL, 0);

if (data == (char *)(-1)) {
    /* Log an error and exit */
}

I.e. Oracle Database does that.

Linux

On Linux these limits are handled via sysctl:

$ /usr/sbin/sysctl kernel.shmmax
kernel.shmmax = 18446744073709551615
$ /usr/sbin/sysctl kernel.sem
kernel.sem = 250        256000  32      1024
             ^ SEMMSL   ^ SEMMNI

You can get sysctl parameters from /proc/sys:

$ cat /proc/sys/kernel/sem
250     256000  32      1024
$ cat /proc/sys/kernel/shmmax
18446744073709551615

Solaris before 10

In Solaris before 10 kernel parameters were used. They are set in /etc/system. You can get actual values from kernel, but only when shmsys and semsys modules are loaded (Solaris lazy-loads them on first syscall):

# modload /kernel/sys/sparcv9/semsys
# modload /kernel/sys/sparcv9/shmsys
# echo 'shminfo_shmmax/J' | mdb -k
shminfo_shmmax:
shminfo_shmmax: 800000
# echo 'seminfo_semmni/J' | mdb -k
seminfo_semmni:
seminfo_semmni: a0000003c

Note that I used /J modifier in mdb which dumps 8-byte in hexademical. On 32-bits builds, you're probably will need /X which dumps 4-bytes.

Solaris 10 and later

Solaris 10 introduced projects, that allow to set these limits with granularity of user or even a process. Use prctl to get appropriate limits:

# prctl -n project.max-shm-memory $$
process: 3451: bash
NAME    PRIVILEGE       VALUE    FLAG   ACTION                       RECIPIENT
project.max-shm-memory
        privileged       474MB      -   deny                                 -
        system          16,0EB    max   deny                                 -
# prctl -n project.max-sem-ids $$
process: 3451: bash
NAME    PRIVILEGE       VALUE    FLAG   ACTION                       RECIPIENT
project.max-sem-ids
        privileged        128       -   deny                                 -
        system          16,8M     max   deny                                 -
# prctl -n process.max-sem-nsems $$
process: 3451: bash
NAME    PRIVILEGE       VALUE    FLAG   ACTION                       RECIPIENT
process.max-sem-nsems
        privileged        512       -   deny                                 -
        system          32,8K     max   deny                                 - 

priviliged values is what you seek