heap profiling

[Evan Laforge]

>> Indeed, though I don't think this is the case, because I get lots of
>> lag even when no logs are written.
>
> In the part you deleted I mentioned one source of lag that does
> not disappear when no logs are written, and a way of using
> profiling cost centers to track down other sources (the ones
> I mentioned accounted for 2/3 of lag in the "profile_logging"
> profile, according to "-hblag -hc -L40" on SCC-annotated
> source).

You mean !s on the intermediate numbers?  I could have sworn I tried
that but no luck.  Thanks for reminding me about manual SCC pragmas,
somehow I totally forgot you could add your own.  Just out of
curiosity, what affect could "return $! 1" have?  A constant should
never be a thunk, so 'seq' on it should have no effect, right?

>> I should go back to poking at the production version.  Even
>> if I don't understand the changes I'm making, at least when
>> I get a speedup I'm more sure it translates to a real speed
>> up in the application.
>
> That way lies madness. Not recommended unless you are
> producing code that noone is ever going to look at again,
> and even then you'll be writing similar code in the future,
> so it is better to put in the energy once to puzzle out
> those mysterious details!-)

Yes, you are right of course, and thank you for the help.  It's just
frustrating when every step toward simpler instead brings new problems
out of the woodwork... but I suppose with enough experience I can
begin to understand those too.  I will resume my testing when I get
some time again!