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Bug#425355: dpt_i2o - disk IO causes very high load



Package: linux-image-2.6.18-4-k7
Version: 2.6.18.dfsg.1-12etch2

Doing any disk IO (> 10MB/s) causes the load on the system to rise into
extreme areas. This is bugging me, especially since the disks (4) are
on a separate RAID controller (Adaptec 2400A, module dpt_i2o).

For example: If I copy a big file via NFS onto the machine, the load
rises easily up to 8 (8 threads configured for nfsd). Copying the same
file via scp, the load gets still up to 5, so it doesn't look like it
is related to NFS. When I check with top what is causing this high
load, I can see that the system is spending all the time in iowaits.

I had this problem also with older kernels. I guess it was just not
that worse, because I just recently upgraded the NIC from 100MBit to
1GBit, causing extra stress for the disks.

Trying to debug things I found a something strange (at least for me).

PCI: Failed to allocate mem resource #6:10000@f8000000 for 0000:01:05.0
PCI: Bridge: 0000:00:01.0
  IO window: disabled.
  MEM window: e8000000-e8ffffff
  PREFETCH window: f0000000-f7ffffff
PCI: Bridge: 0000:02:05.1
  IO window: disabled.
  MEM window: disabled.
  PREFETCH window: disabled.
PCI: Bridge: 0000:00:10.0
  IO window: 2000-2fff
  MEM window: e9000000-e90fffff
  PREFETCH window: ea000000-ebffffff

0000:01:05.0 -> graphics card (AGP, nVidia nv15)
0000:02:05.1 -> PCI bridge of the RAID controller
                Why is the IO/MEM/PREFETCH window disabled?

Attached is also the full output of dmesg, lspci, /proc/interrupts,
/proc/iomem and /proc/ioports.

Could that be the reason for the high load?

cheers,
    Peter

-- 
Peter Hirdina <Peter.Hirdina@gmx.net>

Attachment: output.iomem
Description: Binary data

Attachment: output.ioports
Description: Binary data

Attachment: output.lspci
Description: Binary data

Attachment: output.dmesg
Description: Binary data

Attachment: output.interrupts
Description: Binary data


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