I did try Very Sleepy, but nothing stood out. Can you recommend a profiler for windows?

Hm. That's the one I use for profiling C code; and I've found it very effective. Effective to the point of detecting a difference between two identical opcodes where one causes a cache miss and the other doesn't.

I'd love to take a look at the output from identical runs with the two builds.

the ones that stand out most (ie, 80%+ worse) do create more perl/xs objects than typical, so perhaps that is where I should start looking?

I'd start by rebuilding the 5.24 without PERL_COPY_ON_WRITE & PERL_HASH_FUNC_ONE_AT_A_TIME_HARD individually and together and see what effect they have.

I believe (perhaps wrongly) that the first is a space for speed tradeoff which might be factor.

The second is an (IMO) unnecessary fix for a non-problem that substitutes a different, more time consuming hashing function for the one used in 5.8.9 for "security reasons". Try replacing PERL_HASH_FUNC_ONE_AT_A_TIME_HARD with PERL_HASH_FUNC_ONE_AT_A_TIME_OLD and see if that makes any difference.

Beyond those guesses, I'd need to see the profiler output.

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"Science is about questioning the status quo. Questioning authority". The enemy of (IT) success is complexity.
In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re^3: Our perl/xs/c app is 30% slower with 64bit 5.24.0, than with 32bit 5.8.9. Why? by BrowserUk
in thread Our perl/xs/c app is 30% slower with 64bit 5.24.0, than with 32bit 5.8.9. Why? by Anonymous Monk

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