Verified IDE performance issues in kernels newer than 2.4.20

[K. Hampf]

BRIEF:
I discovered the 2.4.21 and  2.4.22 kernels give me roughly 15% of the 
troughput compared to 2.4.20. Anyone working on this?

Dear Sirs!

I could not find any info about this issue that indicated you were aware of 
this issue. So I decided to send you a report. I've confirmed the issue on 
different i386 chipsets so I think it's a valid issue. Tried to mail the 
maintaners bug-report e-mail (bugs@xxxxxxxxxxxxx) but failed on delivery, 
"User unknown".

I'm a bit into tweaking kernels and I've made a discovery explaining getting 
poor performance in ATA transfers. Both experienced by using apps and with 
"hdparm -t -T" runs.

I verified this under my VIA KT333 and a SiS 735 (SiS 5513IDE) chipsets. The 
first on my Debian testing/unstable workstation, the latter on a 
Debian/stable. It's not debian-kernel specific as I use both "vanilla" stable 
kernel sources and debian sources, I know that I'm on to something.

I have no time to push the 2.4.20 IDE driver tree into 2.4.22 (tried quickly 
but the include headers break and it would take some time for me to make it 
work), I could however, if you take this bugreport seriously and make it 
meaningful, do some runs on vanilla 2.4.20 and 2.4.22 kernels with hdparm and 
send all results. All you need is to tell me. I will be able to test it on a 
newer P4 SATA system too if that's supported when I get to it.

I know this is not a proper nor well formatted bugreport but I could find no 
info on wether you knew of this performance issue already and are working on 
it, I'll throw you some extra info just to make you happy:

Both test systems are Athlon architectures (T-bird 1.2GHz and an XP2100+). 
I've confirmed the issue on different IDE chipsets and on both ATA66, ATA100 
and ATA133 drives. I'm experienced with linux and hardware and know I'm not 
ranting about some "might be" issue. I'm preparing my local LUG to test this 
out a bit more, hopefully on other architectures than i386 also (SPARC and 
Alpha I hope).

If this is relevant to your work on the IDE driver (as I can't get in touch 
with you guys directly) or you might think it's about some PCI issues or 
other things, do not hesitate to contact me, I can include statistics and do 
better testruns if you tell me it would be of any value to you and that you 
are the ones to handle it.

Best Regards,
K. Hampf <khampf@xxxxxxxxxxxxxxxxxxxxx>

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