NAME
eqmemsize — determines the minimum size (in pages) of the equivalently mapped reserve pool
VALUES
Allowed values
0
or any positive integer.
However, because this represents physical pages no longer available for general
system use, caution is urged before using large values.
DESCRIPTION
Equivalently mapped memory is a page which has the same physical and virtual
address.
This is useful for some applications, and for I/O.
Since most memory is to be used in the traditional swapper/virtual address model,
it is useful for the system to reserve some pages for this type of access
at boot while the most physical memory is available.
eqmemsize
provides the bottom value for the size of this reserved pool.
The actual pool size is the sum of
eqmemsize
and a value determined dynamically at boot using the available size of physical
memory, to account for large memory systems automatically.
The scaled value increases the pool size by 1 page per 256 MB.
Who is Expected to Change This Tunable?
Anyone.
Restrictions on Changing
Changes to this tunable take effect at the next reboot.
When Should the Value of This Tunable Be Raised?
This tunable should raised if the customer sees the error message:
Equivalently mapped reserve pool exhausted;
Overall application performance may be improved by
increasing the eqmemsize" tunable parameter"
(currently set to {X}")."
What Are the Side Effects of Raising the Value?
Physical memory is reserved for this use and unavailable for the rest of
the system.
Increasing this tunable by a substantial amount would be roughly equivalent
to removing the same amount of physical memory.
It is not likely to be used for equivalent memory, and no one else
can get to it either.
When Should the Value of This Tunable Be Lowered?
In general, if the tunable is set to more than 10 pages over
15+(physical_memory/256 MB), it's probably too high.
Specifically, if the system swaps heavily, and the above is true, the
value should be lowered to free the physical memory back to the system.
What Are the Side Effects of Lowering the Value?
Requests for equivalent memory may be denied.
This is not a fatal error, but it should be avoided.
What Other Tunable Values Should Be Changed at the Same Time?
None.
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
eqmemsize
was developed by HP.
Printable version
