> On 07/25/2011 06:42 AM, Xinliang David Li wrote: >> FYI the performance impact of this option with SPEC06 (built with >> google_46 compiler and measured on a core2 box). The base line number >> is FDO, and ref number is FDO + reorder_with_partitioning. >> >> xalancbmk improves> 3.5% >> perlbench improves> 1.5% >> dealII and bzip2 degrades about 1.4%. >> >> Note the partitioning scheme is not tuned at all -- there is not even >> a tunable parameter to play with. >
I looked at the bzip2 slowdown years ago and back then it was code layout issue: i.e. adding a nops at place code was offlined actually returned the performance. It was couple years back and thus deifnitely on different CPY than what David use. Bzip2 has tight internal loops sorting the strings, so the layout issues are however quite likely explanation. Honza
