Re: [2.6.10-rc1 and prev] System unuseable while writing to disk

[Nick Piggin <nickpiggin@yahoo.com.au>]

Prakash K. Cheemplavam wrote:

> 100  0
>  0  0      0 774876  14532 136460    0    0     0     0 1180   436  1 0 
> 99  0
>  1  1      0 571740  14732 333736    0    0    32 42628 1325   633  3 43 
> 52  2
>  2  2      0 217812  15072 676648    0    0     0 45184 1523  1771 14 
> 78  0  8
>  1  2      0 220436  15072 676648    0    0     0 49664 1582  1365  9 6  
> 0 85
>  0  2      0  85460  15984 808012    0    0   164 73984 1487  1143 18 
> 32  0 49
>  0  1      0  85716  15984 808140    0    0     0 29056 1493  1381  4 6  
> 0 90
>  0  1      0  86100  15984 808140    0    0     0 40320 1420  1367  3 2  
> 0 95
>  0  1      0  86100  15984 808140    0    0     0 44416 1386   693  0 2  
> 0 98
>  0  1      0  86100  15984 808140    0    0     0 50304 1518  1413  5 6  
> 0 89
>  0  1      0  86164  15984 808140    0    0     0 28544 1452   827  1 2  
> 0 97
>  0  1      0  86292  15984 808140    0    0     0 35840 1386   809  1 2  
> 0 97
>  0  1      0  86356  15984 808140    0    0     0 37376 1450  1373  3 3  
> 0 94
> procs -----------memory---------- ---swap-- -----io---- --system-- 
> ----cpu----
>  r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy 
> id wa
>  1  1      0  86484  15984 808140    0    0     0 42880 1752  2494  7 6  
> 0 87
>  0  1      0  86484  15984 808140    0    0     0 31872 1608  2098  7 4  
> 0 89
>  0  1      0  86484  15984 808140    0    0     0 45952 1530   795  1 2  
> 0 97
>  0  1      0  86484  15984 808140    0    0     0 44288 1515   814  0 3  
> 0 97
>  0  1      0  90580  15984 808140    0    0     0 29052 1471  1365  5 5  
> 0 90
>  1  0      0  90148  16108 809356    0    0   976  2088 1383  1319 22 
> 11  0 67
>  0  0      0  90148  16108 809360    0    0     4    16 1444   833 10 5 
> 84  1
>  0  0      0  90148  16108 809360    0    0     0     0 1256   473  0 0 
> 100  0
>  0  0      0  90148  16108 809360    0    0     0     0 1379   611  3 1 
> 96  0
>  0  0      0  90148  16108 809360    0    0     0     0 1526  2439 16 5 
> 79  0
>  0  0      0  90148  16164 809360    0    0     0   120 1563  1824 16 4 
> 80  0
> 
> 
> Beginning and end the system is idle and then I start writing down the 
> file. During that time thunderbird gets unusable.
> 

It looks like it may be a CPU scheduler issue: Nothing needs to
be read, no swap activity, enough free memory.

However, it also does look like there is a lot of CPU power free,
which makes the cpu scheduler less likely... Maybe interrupts are
using a lot of CPU time or latency, and that is being hidden from
CPU time accounting.

I think Ingo did notice quite large latencies in disk interrupts,
although whether that would be enough to make thunderbird "unusable",
I'm not sure.