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(ipc.info)semlimits

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Limits on Semaphore Resources
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Sizeof various structures:
     semid_ds    44   /* 1 per semaphore array .. dynamic */
     sem          8   /* 1 for each semaphore in system .. dynamic */
     sembuf       6   /* allocated by user */
     sem_undo    20   /* 1 for each undo request .. dynamic */

Limits :
   * SEMVMX  32767  semaphore maximum value (short).

   * SEMMNI  number of semaphore identifiers (or arrays) system
     wide...policy.

   * SEMMSL  maximum  number  of semaphores per id.  1 semid_ds per
     array, 1 struct sem per semaphore => SEMMSL =  (PAGE_SIZE -
     sizeof(semid_ds)) / sizeof(sem).  Implementation maximum SEMMSL =
     500.

   * SEMMNS  maximum number of semaphores system wide ... policy.
     Setting SEMMNS >= SEMMSL*SEMMNI makes it irrelevent.

   * SEMOPM 	Maximum number of operations in one semop
     call...policy.

Unused or unimplemented:
SEMAEM  adjust on exit max value.
SEMMNU  number of undo structures system-wide.
SEMUME  maximum number of undo entries per process.