On 03/29/10 15:41, ольга крыжановская wrote:
The libc mem* instructions use VIS but they are still suboptimal for
small fixed size copies because they impose a significant overhead by
*always* testing the size and alignment. For copies smaller than 48
bytes the overhead is even greater than the size of data copied,
making it inefficient compared to an inlined chain of VIS
instructions.
Olga
I would be surprised if VIS offered any real advantages in
copies of less than 48 bytes; perhaps if the copies are
misaligned VIS may help. Be very careful about inlining
memcpy; while this improves performance on microbenchmarks,
the adverse effects of icache hit rate on real world code
generally leads one in the other direction.
- Bart
--
Bart Smaalders Solaris Kernel Performance
bart.smaald...@oracle.com http://blogs.sun.com/barts
"You will contribute more with mercurial than with thunderbird."
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