I can confirm this problem in Hardy. It is an easily visible regression
on my laptop somewhere between kernels 2.6.24-7-generic and
2.6.24-11-generic. Fortunately I kept the old -7 kernel so I can compare
the results. Today I upgraded to 2.6.24-12-generic and the problem still
persists.

I don't know if there's any archive of kernel deb binaries for all the
versions between -7 and -11 -- if I had them I could exactly pinpoint
the version which caused the regression.

The problem is clearly related to disk I/O. With a large I/O operation,
like copying an ISO file, the system becomes very unresponsive, mouse is
jerky, I have trouble switching between terminal windows or from X to
the virtual terminal (ctrl-alt-f1). If I start a large enough disk
operation, it can starve the system resources so that only a hard reboot
can help.

The laptop is HP Compaq nx5000 with Pentium M 1.7 GHz, 1GB RAM, 80GB
SATA disk, latest Hardy Heron.

Here's a comparison of:
$ time cp -p valhalla-i386-disc1.iso z
(copying a 650M file on the same filesystem -- XFS)

Linux fafik 2.6.24-7-generic #1 SMP Thu Feb 7 01:29:58 UTC 2008 i686 GNU/Linux
real    0m35.307s
user    0m0.060s
sys     0m2.556s

Linux fafik 2.6.24-12-generic #1 SMP Wed Mar 12 23:01:54 UTC 2008 i686 GNU/Linux
real    5m31.690s
user    0m0.340s
sys     1m11.932s

$ cat /proc/version_signature
Ubuntu 2.6.24-12.22-generic

During the slow I/O operation, top seems to indicate that some kernel
daemons like kondemand, kblockd take a significant amount of CPU.
Obviously load average skyrockets.

top - 21:57:33 up 6 min,  3 users,  load average: 8.87, 6.21, 2.68
Tasks: 117 total,   3 running, 112 sleeping,   0 stopped,   2 zombie
Cpu(s):  3.7%us, 27.4%sy,  0.0%ni,  0.0%id,  2.0%wa,  5.0%hi, 61.9%si,  0.0%st
Mem:   1027128k total,  1012132k used,    14996k free,      100k buffers
Swap:        0k total,        0k used,        0k free,   802832k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND            
 6389 wanted    20   0  3140  772  644 R 42.9  0.1   0:52.41 cp                 
 1812 root      15  -5     0    0    0 S  8.6  0.0   0:02.76 scsi_eh_1          
 5347 uml-net   20   0  1708  428  360 S  5.3  0.0   0:03.76 uml_switch         
   43 root      15  -5     0    0    0 S  4.6  0.0   0:05.78 kblockd/0          
 4223 root      15  -5     0    0    0 S  4.6  0.0   0:00.84 kcryptd            
 5585 root      20   0  3408 1128  976 S  4.6  0.1   0:03.12 hald-addon-stor    
 4970 root      15  -5     0    0    0 S  4.0  0.0   0:06.80 kondemand/0        
 1479 root      15  -5     0    0    0 S  3.3  0.0   0:01.50 ata/0              
 2994 root      15  -5     0    0    0 S  3.3  0.0   0:09.86 ipw2200/0          
 5678 root      20   0  210m  10m 6720 S  3.3  1.0   0:08.70 Xorg           

** Attachment added: "lspci-vvnn.log"
   http://launchpadlibrarian.net/12676983/lspci-vvnn.log

-- 
Occasionally, disk goes crazy, system freezes
https://bugs.launchpad.net/bugs/174185
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