IDE performances, 2.4 vs 2.5

[Stefano Rivoir <s.rivoir@gts.it>]

Noting that 2.5 is much slower than 2.4 on disk operations (you *touch* 
it when you have not-so-fast machine and use KDE, for example), I've 
written a silly test that fwrite/fread a single 100Mb file, char by 
char, and timing it I have results that I can't understand very well. Of 
course, same machine, same hdparm settings, same processes running 
(none, it's a notebook without server processes). I've run these test 
several time, the results are always more or less the same (ext2):

2.4.19

   read:    real    0m15.822s
            user    0m15.180s
            sys     0m0.270s

   write:   real    0m12.524s
            user    0m11.800s
            sys     0m0.690s

2.5.70 (up to -bk14, and -mm6)

   read:    real    0m20.790s
            user    0m14.372s
            sys     0m0.949s

   write:   real    0m13.148s
            user    0m11.901s
            sys     0m0.665

Writing does not drop, but reading has a 6 seconds difference between 
user+sys and real that I can't figure out. And the total difference is 
"huge". Actually, using anything that touches the disk (it can be a 
trivial "aptitude" loading the cache, or a complex KDE) slows down.

I've run these tests on a HP Omnibook w/Celeron, but I have the same 
slow down on a Athlon K7.

Is it anyway "normal", something I should expect upgrading from 2.4 to 
2.5/2.6? Or there should be something I should check more accurately?

Bye all.

-- 
Stefano RIVOIR