Re: [gentoo-user] genlop times was: migrating to gcc-3.4.4

[Willie Wong]

On Thu, Aug 25, 2005 at 11:51:32AM +0000, Fernando Meira wrote:
> I have a P4-2.4GHz laptop.
> I forgot to say that the estimation time was made by genlop. And was quite
> wrong! It took something like 11h to compile 112 packages, (though I've
> interrupted while compiling gcc-3.3.6.. so it had to restart it anew). From
> this, I don't know if I should trust genlop anymore.. or is there something
> to configure so that it is more accurate?
>
> Just for the record, the migration to gcc-3.4.4 went just fine.. until now
> at least. :)

hum. Genlop looks at the past emerge times of the packages, calculates
an average based on that. 

The one thing genlop can't do is figure out how long it takes to merge
new packages. So it just skips them. That is the only way I see genlop
being wrong by so much. (The other possibility is that you were
running the box with a high load WHILE compiling, though I guess you
won't be complaining if that were the case.)

To be honest, I've found the genlop time quite reliable... I've
rebuilt my systems with --emptytree a few times in the past 6 months.
(Once after killing PAM and LDAP, once after changing to hardened,
once after changing from ~x86 to x86, and once after a major rehaul of
my USE flags; these are on my desktop machine only). The 500 or so
packages came up to be 1 day and 15 hours from genlop. The actual
compiles never took more than 2 days, and that was while the computer
was still in use. Once it actually finished before the estimated time. 

Do note that, however, genlop can only calculate its merge time based
on past averages. So if you made major changes to your system, or if
the codebase changed significantly upstream, genlop can be completely
wrong. For example, looking at past emerges of glibc, I see the
compile time goes from everything between 28 minutes to 3 hours.
genlop tells me that if I were to remerge glibc it would take me 1
hour and 9 minutes. But I know from experience if I were to install
2.3.5-r1, it will most likely only take me 40 minutes, and if I were
to compile glibc-2.3.4.20050125-r1, it will take me about 2 hour and
10 minutes. Why the funky discrepancy I don't know. So I think that
while genlop is generally rather reliable for a rough idea on how long
I need to wait for the compile (i.e. is it worth it just sitting here
reading a book or should I just go to bed), the numbers it give should
be taken with a grain of salt if you don't have a large number of
history of emerges for it to base its guesses on. 

W

-- 
"Anyone who is capable of getting themselves made President 
should on no account be allowed to do the job." 

- Some wisdom from The Book. 
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