2.6.27 - 2.6.29 upgrade.. RAID 0 CCISS now slower

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 ?

 

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?

 

Custom.. but

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.

 

Hm, I have no idea why this is happening.

 

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?

 

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

 

Mailing list it is

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!)