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

["Prakash K. Cheemplavam" <prakashkc@gmx.de>]

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Nick Piggin wrote:
> 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.

I see this behaviour with default scheduler in vanilla and with staircase...


> 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.

I tried preempt (inkl preempt "big kernel lock" in ck) which doesn't 
avoid above. (I don't rember whether it was better, though.)

bye,

Prakash

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