Warnings

If you optimize at –xO3 or –xO4 with very large procedures (thousands of lines of code in a single procedure), the optimizer might require an unreasonable amount of memory. In such cases, machine performance can be degraded.

To prevent this degradation from taking place, use the limit command to limit the amount of virtual memory available to a single process (see the csh(1) man page). For example, to limit virtual memory to 4 gigabytes:

example% limit datasize 4G

This command causes the optimizer to try to recover if it reaches 4 gigabytes of data space.

The limit cannot be greater than the total available swap space of the machine, and should be small enough to permit normal use of the machine while a large compilation is in progress.

The best setting for data size depends on the degree of optimization requested, the amount of real memory, and virtual memory available.

To find the actual swap space, type: swap– l

To find the actual real memory, type: dmesg | grep mem