The SPUs seem to become VERY irrealistic

Matthias Benkmann matthias at winterdrache.de
Fri Oct 18 14:41:51 PDT 2002


On Fri, 18 Oct 2002 23:25:10 +0200 "Florian Hess (FLoH)" <hipabos at web.de>
wrote:

> Hi lfs-experts,
> 
> All went well - until the gcc compilation in ch5 (lfs4.0). My 
> measurement of 1 SPU = 892sec is no more realistic at all. The 
> compilation has been started 6:28p, and 10:35p (for 4h instead of 
> approx 2,5h) the process was still in the make phase. I get more and 
> more uneasy (Why I don't know. "coolness" is not really one of my 
> strengths). How long will the glibc take, then?

Looooooooooooooooooooooooooooooooooong.

> 
> Can that happen, and how? 

Yes. There's more to computer speed than just MHz. Processor cache size
for instance plays a role. And these factors are all non-linear. A
processor with twice the amount of cache is not twice as fast. For a
program that is very localized, the cache may not have an effect, but some
other program might get a large speed boost.
In other words: Your old Pentium 150MHz won't just take 10 times the time
of an Athlon 1.5GHz for the same task. On some tasks it may take 20 times
or more time because of architectural differences.

>My system is: P150, 16mb + 300mb Swap space, 
> Debian Potato, CD1 (all development tasks installed).

That system is very old. I don't think many systems of this type went into
the SBU average. I think 6h is still a reasonable time for gcc on such a
system. I wouldn't worry if I were you. Programs hanging in endless loop
are very rare. Usually they'll crap out with a segfault or something
similar.

MSB

-- 
If everything seems to be going well, you have obviously overlooked
something.

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