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

From: Nick Piggin
Date: Thu Nov 11 2004 - 02:35:20 EST


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.
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