System extremely slow under light load

[Bartosz Fabianowski]

Hi list

I am having problems with my 8.2-STABLE laptop. At times, even a very 
light load makes the system grind to a halt. Once an application is in 
the foreground, I can interact with it just fine. But when I click on a 
long-unused menu item or try to switch applications, I have to wait 
dozens of seconds or even minutes. It feels as if things were being 
swapped in very slowly. However, top says otherwise:

The box has 4 GB of RAM with only 680 MB used. On top of that, 69 MB of 
swap are in used. That last number does not seem to be changing, so 
nothing is being swapped in or out.

The load that seems to cause the worst problems is an import of 
OpenStreetMap data into a PostgreSQL 9 database. This does not exercise 
the CPU (a Core i7 Quad) much as CPU load hovers around the 20% mark 
most of the time and powerd is happy to reduce the operating frequency 
down to a few hundred MHz. There also does not seem to be much disk 
activity.

So, memory, CPU and disk all seem fine. And still, whenever I try to 
switch applications, I have to wait minutes for them to appear. I am 
having a hard time figuring out what is going on. Any tips would be 
greatly appreciated.

I am including the outputs of vmstat -c 2 and iostat -c 2 in the hope 
that these may shed some light on this.

Thanks,
- Bartosz Fabianowski


vmstat -c 2
  procs      memory      page                    disks     faults 
   cpu
  r b w     avm    fre   flt  re  pi  po    fr  sr ad0 cd0   in   sy 
cs us sy id
  0 1 20  21376M   203M  1652   2   1   1  2993 289   0   0   90  949 
2764  5  2 93
  0 0 20  21378M   197M  1332   0   5   1  2165   0  58   0  208 7875 
3614  2  2 96


iostat -c 2
        tty            ada0              cd0            pass0 
   cpu
  tin  tout  KB/t tps  MB/s   KB/t tps  MB/s   KB/t tps  MB/s  us ni sy 
in id
  188  2367 51.73  22  1.12   0.00   0  0.00   0.00   0  0.00   3  1  2 
  0 93
    1   991 18.06  49  0.86   0.00   0  0.00   0.00   0  0.00   3  0  2 
  0 94