Specifying cache sizes
If your program is intended to run exclusively on a single machine or configuration, you can help the compiler tune your program to the memory layout of that machine by using the FORTRAN -qcache option.
You must also specify the -qhot option for -qcache to have any effect. The -qhot option uses the -qcache information to determine appropriate memory-management optimizations.
There are three types of cache: data, instruction, and combined. Models generally fall into two categories: those with both data and instruction caches, and those with a single, combined data/instruction cache. The TYPE suboption lets you identify which type of cache the -qcache option refers to.
The -qcache option can also be used to identify the size and set associativity of a model's level-2 cache and the Translation Lookaside Buffer (TLB), which is a table used to locate recently referenced pages of memory. In most cases, you do not need to specify the -qcache entry for a TLB unless your program uses more than 512 KB of data space.
There may be cases where a lower setting for the SIZE attribute gives enhanced performance, depending on the system load at the time of a run.