On 30/04/2016 12:10 AM, Peter Relson wrote:
Since the origin for the starting post apparently lay in branching around the eyecatcher (which really is not necessarily at all the same as a branch in a 2 instruction loop), I was surprised that none of the posts that I glanced at mentioned Instruction-cache misses.
Good point well made but can you explain why changing a B to a BE in a tight loop results in 43% difference?
Just because you think something is high frequency does not mean that the operating system or the machine agrees with you. If the module's first instruction is not in I-cache, then whether that first instruction is a branch or anything else, it will show up as a lot hotter than a somewhat similar instruction that is in the I-cache.
Indeed. But why would there be a slowdown on a z13 when compared to older hardware?
Peter Relson z/OS Core Technology Design ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
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