XL Fortran Enterprise Edition for AIX : User's Guide - IBM

2 Level-2 cache or the table lookaside buffer (TLB) if the machine has
no level-2 cache
3 TLB in a machine that does have a level-2 cache
Other levels are possible but are currently undefined. If a system has more
than one level of cache, use a separate -qcache option to describe each
level.
line=bytes
Specifies the line size of the cache.
size=Kbytes
Specifies the total size of this cache.
type={C|c| D|d|I|i}
Specifies the type of cache that the settings apply to, as follows:
v C or c for a combined data and instruction cache
v D or d for the data cache
v I or i for the instruction cache
Restrictions
If you specify the wrong values for the cache configuration or run the program on
a machine with a different configuration, the program may not be as fast as
possible but will still work correctly. Remember, if you are not sure of the exact
values for cache sizes, use a conservative estimate.
Currently, the -qcache option only has an effect when you also specify the -qhot
option.
Examples
To tune performance for a system with a combined instruction and data level-1
cache where the cache is two-way associative, 8 KB in size, and has 64-byte cache
lines:
xlf95 -O3 -qhot -qcache=type=c:level=1:size=8:line=64:assoc=2 file.f
To tune performance for a system with two levels of data cache, use two -qcache
options:
xlf95 -O3 -qhot -qcache=type=D:level=1:size=256:line=256:assoc=4 \
-qcache=type=D:level=2:size=512:line=256:assoc=2 file.f
To tune performance for a system with two types of cache, again use two -qcache
options:
xlf95 -O3 -qhot -qcache=type=D:level=1:size=256:line=256:assoc=4 \
-qcache=type=I:level=1:size=512:line=256:assoc=2 file.f
Related Information
See “-qtune Option” on page 251, “-qarch Option” on page 127, and “-qhot
Option” on page 171.
138 XL Fortran Enterprise Edition for AIX : User’s Guide