From: Clifford Heath <no@...>
Date: 2007-11-11T08:45:04+09:00
Subject: Re: enterprise ruby

M. Edward (Ed) Borasky wrote:
> I'm in the process of re-factoring the Rakefile from my profiling 
> efforts. I'd be happy to profile your source as part of that. By the 
> way, are you starting with 1.9 or 1.8? I'm still profiling 1.8 only, but 
> I expect to have 1.9 profiling working within a week or so.

What profiler are you using Ed? I just ask because I wrote a profiler
a decade ago that used gcc's -pg (gprof profiling) with a custom prof
library that used tail patching and the TSC register to get real-time
nano-second resolution on profiled functions, including parent/child
rollups.

The use of *real-time* in profiling is fantastic, because it tells you
where, for example, I/O or excessive page-faulting is hurting some
function. I also hooked the memory allocation functions to gather
memory info, including both growth and flow (in/out). To carefully
select functions to profile, rather than profiling all, also helps a
lot. Finally, the TSC register counts processor cycles, so you get
nanosecond-resolution.

A lot of Unix-based systems are designed using flawed performance data
from the kernel (statistical) profiling, that simply doesn't see I/O
or VM times.

I've no idea whether the hacks I used to do the tail-patching still
work with a current gcc, but it would be good to reactivate tprof if
possible. It'd be great to have a Ruby that can do such profiling.
I still have the code somewhere...

Clifford Heath.