Extremely poor performance crunching random numbers under PIV-FC5
Andy Green
andy at warmcat.com
Fri May 19 16:45:00 UTC 2006
BankHacker wrote:
> 1.- Andy told me to make my own bankhacker_random_r() function and
> avoid glibc's (libc.so.6). I am going to work on it, but it is not
> easy, I think.
What I meant by this was to make an empty implementation of random_r()
in a tiny dynamic lib. In this way you isolate if the problems come
from something glibc random_r() does, or if there is some terrible
problem with dynamic libs for that processor/compiler/compile environment.
> 2.- Jakub told that "On PIV, atomic instructions are horribly
> expensive. Either you have preloaded some library that called
> pthread_create, or your CPU is unable to do the jump around lock
> prefix trick quickly." It sounds very interesting but I don´t know how
> to handle this ... any further explanation would be a great hint.
> Thanks!
I didn't really understand what Jakub was telling with this (it seems
that the compiler would react to expecting needing threadsafety in an
expensive way?) but as I understood it the random_r() test was intended
to test around this case.
-Andy
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