Long IO pauses

[Jan Dittmer <jdi@l4x.org>]

Doing 10*bonnie++ and a cp of a 1 gb taking ages (2+h), this interesting
vmstat strace can be produced. Notice the ~28s of almost no i/o
activity.

Setup is ext3 on dm-crypt on loop on RAID5. Kernel 2.6.18, amd64,
cfq io scheduler. Changing the scheduler to deadline leads to the
same result. Seems to be seek bound would be my guess. But
virtually _no_ io for 30s??

Ideas?

Thanks,

Jan


procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
27  2      0  15948   7184 1671096    0    0    42   531   71   99 49  1 47  3
24  2      0  15496   7168 1669868    0    0    28 85196 2596 3840 33 67  0  0
26  2      0  14696   7212 1673868    0    0   104 71388 2384 7371 32 68  0  0
26  1      0  16368   7216 1662732    0    0   412 79600 2258 6644 37 63  0  0
26  0      0  16320   7232 1668900    0    0    40 97080 2212 9306 33 67  0  0
25  0      0  15324   7212 1668804    0    0     4 109204 2290 8091 34 66  0  0
27  0      0  16648   7232 1670416    0    0     0 100952 2329 10752 34 66  0  0
23  2      0  15628   7292 1675568    0    0    92 88624 1595 1853 30 64  0  7
26  1      0  16232   7356 1674360    0    0     0 101036 1926 5837 36 64  0  0
28  1      0  16368   7432 1671596    0    0     4 99812 1601 12745 32 69  0  0
27  2      0  15296   7460 1674416    0    0    20 101932 1641 4563 35 65  0  0
 1 22      0  17924   7440 1677156    0    0   416 67320  990 4569 31 54  0 15
 0 23      0  20668   7480 1677964    0    0   100 69324 2630 39412  0 23  4 73
 0 23      0  24756   7480 1677992    0    0     8  3368 1609 15392  0  6  0 94
 0 22      0  27740   7492 1678032    0    0    20  3840 1524 15311  0  4  1 95
 0 23      0  28368   7508 1678048    0    0    16 10460 1545 16908  0  8  1 91
 0 22      0  29368   7508 1678060    0    0    44 51828 2445 35456  0 18  4 77
 0 22      0  30244   7508 1678112    0    0     0 53984 2020 32759  0 19  2 79
 0 22      0  38400   7524 1678104    0    0     0 22644 3493 20678  0 14  3 83
 0 22      0  39284   7524 1678104    0    0     0    16  474  403  0  0  0 100
 0 22      0  40400   7524 1678112    0    0     0     0  458  310  0  0  0 100
11 22      0  41532   7532 1678112    0    0     0    32  567  532  0  1  0 99
 0 22      0  42540   7532 1678112    0    0     0    24  472  497  0  0  0 100
 0 22      0  43544   7532 1678112    0    0     0     8  467  374  0  0  0 100
 1 22      0  44668   7540 1678104    0    0    12     0  502  367  0  0  0 100
 0 22      0  47716   7540 1678112    0    0     0     0  466  322  0  0  0 100
 0 22      0  51932   7540 1678120    0    0     0     0  548  336  0  0  0 100
 0 22      0  55360   7540 1678120    0    0     0     0  464  320  0  0  0 100
 0 22      0  55492   7540 1678120    0    0     0     0  463  307  0  0 15 85
 4 22      0  55492   7568 1678108    0    0    12   100  504  705  0  1 24 76
 1 22      0  55616   7568 1678120    0    0     0     0  481  333  0  0 15 84
 0 22      0  55748   7568 1678120    0    0     0     0  585  373  0  0 50 50
 0 22      0  55872   7568 1678120    0    0     0    12  467  359  0  0 50 50
 0 22      0  55872   7568 1678120    0    0     0     8  463  341  0  0 50 50
 0 22      0  55996   7568 1678120    0    0     0     0  457  290  0  0 50 50
 0 22      0  55996   7588 1678112    0    0     4    76  490  499  0  0 50 50
 0 22      0  55988   7600 1678108    0    0     4    48  614  721  0  0 13 87
 0 22      0  55988   7600 1678120    0    0     0     0  501  371  0  0  0 100
 0 22      0  56112   7600 1678120    0    0     0     0  465  311  0  0  0 100
 0 23      0  56064   7660 1678184    0    0   120     0  488  449  2  1  0 97
 0 24      0  43684   7712 1682604    0    0  4416   104  600 1161  2  2  0 97
 0 24      0  43692   7712 1682568    0    0     0     0  550  363  0  0  0 100
25 19      0  26712   7752 1696056    0    0   264  5872  763  945 11  7  0 82
26 12      0  16496   7800 1712788    0    0   632 44172  515 4054 38 53  0  9
26 11      0  17012   7804 1712036    0    0    48 69440 1019 8243 38 61  0  1
24  4      0  16884   7704 1709856    0    0   128 107284 2580 3877 32 68  0  0
24  5      0  15908   7696 1713756    0    0   652 54496  810 7612 35 66  0  0
25  0      0  15840   7648 1716956    0    0     4 47380  487 3883 40 60  0  0
26  1      0  16592   7496 1714384    0    0   752 52372 1008 2668 40 60  0  0
26  2      0  15952   7348 1712756    0    0    16 79500 1483 2703 35 65  0  0
25  1      0  15888   7208 1710392    0    0   124 121924 1997 2713 35 65  0  0
25  0      0  16900   7048 1707220    0    0     0 107020 1829 2865 33 67  0  0
25  1      0  16804   6968 1715120    0    0   336 101068 1909 5316 33 65  0  2
29  2      0  15628   6928 1720472    0    0   712 51644  710 6218 38 62  0  0
26  0      0  15360   6708 1718540    0    0     0 78944  997 13772 30 70  1  0
24  5      0  16996   6588 1714992    0    0    20 120532 2318 10112 32 68  0  0
30  5      0  16972   6612 1712060    0    0   276 97880 1756 3526 37 63  0  0
27  3      0  16312   6512 1718500    0    0    20 102096 1981 4503 34 66  0  0
25 16      0  15672   6836 1712320    0    0  1324 29048  761 2265 39 36  0 25
28  8      0  16704   6760 1709436    0    0   100 73980 1172 3956 36 64  0  0
29  5      0  16640   6696 1707612    0    0     0 119576 2498 16484 31 69  0  0
27  8      0  16316   6504 1706384    0    0    12 96948 2601 11700 32 68  0  0
25  4      0  16100   6488 1714172    0    0    52 82184 1682 4525 33 67  0  0
24 20      0  16744   6532 1712988    0    0   532 51036  560 4602 38 62  0  0
29 14      0  17128   6528 1709740    0    0    32 74436 1342 5652 34 66  0  0
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