Improve performance by locking memory on HP-UX 10.2

ModelSim 5.3 and later versions contain a feature to allow HP-UX 10.2 to use locked memory. This feature provides significant acceleration of simulation time for large designs - i.e. with a memory footprint > 500Mb. (Test cases showed 2x acceleration of large simulations.) The following steps show how to set up the HP-UX 10.2 so memory can be locked.

1. Allow the average-user to lock memory. By default, this privilege is not allowed, so it has to be enabled. To allow everyone MLOCK privileges, the administrator needs to execute this command on the machine that will be running ModelSim:

/usr/sbin/setprivgrp -g MLOCK 

To only allow a particular group MLOCK privileges, use the command:

/usr/sbin/setprivgrp <group-name> MLOCK

This allows you to lock memory. No other privileges are enabled.

2. Once the MLOCK privilege is enabled, you merely have to modify the modelsim.ini file, and add the following entry to the [vsim] section:

LockedMemory = <some-value> 

Where <some-value> is an integer representing the number of megabytes of memory to be locked. Once this is done, the memory will be locked when vsim invokes (using this .ini file).

ModelSim will not lock more memory than is available in the system. The maximum memory that can be locked is: system physical memory (RAM) - 100 Mb = locked memory

When ModelSim locks memory, other processes will not have access to it. Therefore, you should consider how much memory is locked on a per-design basis to avoid locking more than is needed.

System parameters used for shared/locked memory may not be set (by default) high enough to take full advantage of this feature in later generations of HP-UX. Using the "sam" program, go to the "Configurable Parameters" window (under "Kernel Configuration"). There are several values that may need to be increased.

First, enable shared memory. The value for "shmem" should be equal to 1. Set the value for "shmmax" as large as possible. The defaults for the values of "shmmin" and "shmseg" should be ok. To change these parameters, you have to rebuild the kernel and reboot.

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