Lockable Memory

[ln_unix]

Can any one please help me understand Lockable memory as am not able to understand from internet and pdf's also.....

Need your help.....
&
Thanks in Advance....

Regards,
LN

[Matti_Kurkela · Accepted solution]

As far as I understand:

"Lockable memory" indicates how much virtual memory pages applications may _optionally_ lock into physical memory so that they won't be paged out. This locking can be done using system calls like mlock(), plock() or shmctl().

If a process locks its memory, it allows that one process to be very responsive to user requests; however, this limits the amount of usable memory available for other processes and may lead to increased paging activity for them.

The amount of lockable memory = physical memory - (memory used by kernel + unlockable_mem kernel tunable)

The default value for the unlockable_mem tunable is 0 (in 11.23 at least). If you have a badly-behaving program that tries to lock all the memory it can get, this tunable could be used to force some of the memory to be left unlocked, so that one process cannot monopolize the entire system.

MK