BW_MEM_CP(8) - LMBENCH man page


NAME

bw_mem_cp - time memory copy speeds

SYNOPSIS

bw_mem_cp size libc|unrolled aligned|unaligned

DESCRIPTION

bw_mem_cp allocates twice the specified amount of memory, zeros it, and then times the copying of the first half to the second half. Results are reported in megabytes moved per second.

The size specification may end with ``k'' or ``m'' to mean kilobytes (* 1024) or megabytes (* 1024 * 1024).

OUTPUT

Output format is "%0.2f %.2f\\n", megabytes, megabytes_per_second, i.e.,


8.00 25.33

MEMORY UTILIZATION

This benchmark can move up to three times the requested memory. Bcopy will use 2-3 times as much memory bandwidth: there is one read from the source and a write to the destionation. The write usually results in a cache line read and then a write back of the cache line at some later point. Memory utilization might be reduced by 1/3 if the processor architecture implemented ``load cache line'' and ``store cache line'' instructions (as well as ``getcachelinesize'').

SEE ALSO

lmbench(8).