HP-UX Reference (11i v1 05/09) - 5 Miscellaneous Topics (vol 9)

shmmni(5) shmmni(5)

(Tunable Kernel Parameters)

What Are the Side Effects of Raising the Value?

Kernel memory usage will be slightly increased, as the data structures used to track the segments are

preallocated based on this tunable.

When Should the Value of This Tunable Be Lowered?

If kernel memory is at a premium, or it is known that few segments will be needed, a slight savings can be

gained from decreasing this tunable, and thus decreasing the data structure memory usage associated with

it.

If System V shared memory is not to be used at all, simply set the

shmem tunable to off instead.

What Are the Side Effects of Lowering the Value?

Kernel memory usage will be slightly reduced.

What Other Tunable Values Should Be Changed at the Same Time?

shmmax and shmseg should be considered. shmseg

should be changed in the same manner as shmmni,

since lowering the total number of segments but raising the number available per process only makes sense

if you want a few processes taking all the segments.

shmmax is more complex and any changes to it really depend on the effect desired. Refer to the

shmmax(5) manpage for more information before changing this tunable.

WARNINGS

All HP-UX kernel tunable parameters are release speciﬁc. This parameter may be removed or have its

meaning changed in future releases of HP-UX.

AUTHOR

shmmni was developed by HP.