2.6.27 - 2.6.29 upgrade.. RAID 0 CCISS now slower

[touchtecservers]

I am using Gentoo on a HP DL380 G3. Intel Xeon (P4) 3.06ghz processors,
with a HP COMPAQ CCISS ARRAY in RAID 0 mode (hardware, linux just sees one single drive)

hdparm on 2.6.27 shows the speed at ~ 130mbs

After performing an upgrade of the kernel

hdparm on 2.6.29 shows the speed at ~ 30mbs (30-50mbs varies)

I looked at the DMESG comparisons,
and the only difference is that 2.6.29 mentions:
"IRQF_DISABLED is not guaranteed on shared IRQs"

Now I have looked for hours to see if it was a configuration issue, but to no avail.

Anyone ?

[falko]

Did you build the new kernel yourself? If so, did you use the old kernel configuration (the one from 2.6.27), or did you configure it manually?

[touchtecservers]

Yes the 2.6.27 kernel was self built, and it works fine. The 2.6.29 was built using the .config file from the 2.6.27.

I compiled this kernel on two servers, both same spec (well, one has 4GB ram other has 2GB ram), same setup - and both responded as above.

On the one, I recompiled the kernel to just use the new version (NO config changes). The other I re-compiled using config changes (removing things not relevant for the machine etc) - both end up having this problem.

I have done a "diff" compare on the configs, but there is nothing I can find that would explain this.

I know that this "IRQF_DISABLED" warning isn't present in 2.6.27 boots, and that the CISS driver works full speed in that one.

I thought it was originally that I changed the IO Scheduling, but as i said, on the one machine - all i did was copy the config file and recompile.

Do you know of anything that could be causing this?

I checked proc/interrupts on both kernel versions, and IRQ 30 is unshared (IO-APIC-FASTEOI cciss or something like that), i am just unsure what is causing the issue.

[falko]

Hm, I have no idea why this is happening.

[touchtecservers]

Fair enough. I was going to join the kernel mailing list - but i don't need that much spam! Any other places I could ask this?

[falko]

No, I think the kernel mailing list would be the best place.

[touchtecservers]

Okay... i've signed up.

If (hopefully when) I get a reply, I will post the answer here, maybe someone else will need the solution too (if there is one!)