[erlang-questions] HiPE performance gain (Was: Re: [erlang-questions] Erlang static linked interpreter)

[Thomas Lindgren]

----- Original Message ----
> From: Ciprian Dorin Craciun <ciprian.craciun@REDACTED>
...
>      More exactly what are the use-cases which are likely to benefit
> from  HiPE? I would guess that in a CPU bound application HiPE would do
> better than  without, but what about network I/O bound applications, or
> applications that  deal mainly with strings (represented as lists), or
> applications that deal  mostly with binary matching?


As far as I'm aware, Hipe mostly can't optimize the runtime system. Sockets, 
drivers, etc, are just invoked. Some BIFs are inlined, but the more complex ones 
are just invoked. Binary matching is (mostly or entirely?) native compiled. List 
traversal should be fast, though the emulator cheats (or at least used to cheat) 
by invoking C code for some common operations. Pattern matching is generally 
fast, though (some?) guards may be invoked instead of inlined.

Our experience on AXD 301 way back was ambiguous, though part of that was due to 
insufficient I-cache on the Ultrasparc -- cache misses ate the other performance 
gains. (This is one of the classic arguments for using an emulator instead of 
native compilation.) Perhaps modern hardware would make better use of the native 
code. 

Anecdotes I've heard from people working on other big code bases indicate no 
clear gains, basically. But I can't claim to comprehensively cover the whole 
field by any means. It would be interesting to hear some testimonials.

(The core erlang app used at my current company is estimated to max out the 
network interfaces without native compilation, so we haven't tried it.)

One system that might have gained is Wings3D, since Hipe spent a good deal of 
effort on floating point optimization. Haven't measured it myself, but it would 
be interesting to hear of any experiences.

Finally, you can always have a look at the Hipe output for a function or module, 
if you want to know the gory details.

Best regards,
Thomas