On Mon, 3 Dec 2007, Neil Brown wrote:
On Sunday December 2, jpiszcz@xxxxxxxxxxxxxxx wrote:
Was curious if when running 10 DD's (which are writing to the RAID 5)
fine, no issues, suddenly all go into D-state and let the read/give it
100% priority?
So are you saying that the writes completely stalled while the read
was progressing? How exactly did you measure that?
Yes, 100%.
What kernel version are you running.
2.6.23.9
Is this normal?
It shouldn't be.
NeilBrown
I checked again with du -sb while it is writing, it is, just just VERY
slowly:
Before reading dd:
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
1 3 104 46088 8 7669416 0 0 0 102832 2683 21132 0 34 43 22
0 2 104 49140 8 7666724 0 0 0 137800 2662 6690 0 30 45 25
0 4 104 47344 8 7668884 0 0 0 93312 2637 19454 0 22 40 38
0 6 104 51292 8 7664688 0 0 0 89404 2538 7901 0 18 31 51
0 1 104 55476 8 7660424 0 0 0 172852 2669 13607 0 39 47 14
0 3 104 50428 8 7665036 0 0 0 135916 2711 22523 0 27 52 22
0 5 104 51836 8 7664152 0 0 0 101504 2491 2784 0 18 42 40
0 5 104 113468 8 7603016 0 0 0 63788 2568 7528 0 24 24 52
0 2 104 45780 8 7669364 0 0 1116 177604 2617 13521 0 34 33 33
After reading dd launched:
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
2 4 104 45076 2379348 5273588 0 0 7584 17753 548 301 0 17 45 39
0 5 104 46632 2617352 5043116 0 0 237908 0 2949 2647 0 10 35 54
1 5 104 45656 2846728 4814900 0 0 229376 0 2768 2360 0 10 36 54
1 4 104 46128 3104932 4551408 0 0 258308 2748 2918 2559 0 11 36 53
0 5 104 43804 3338248 4323996 0 0 233212 0 2815 2631 0 10 33 57
0 5 104 46580 3534856 4125848 0 0 196608 0 2736 2273 0 9 36 55
0 5 104 46164 3797000 3862936 0 0 262144 1396 2900 2834 0 11 37 51
1 4 104 46076 4026376 3633740 0 0 229376 0 2978 2586 0 11 37 53
0 5 104 46252 4288520 3371724 0 0 262144 0 2878 2316 0 11 37 53
0 5 104 46520 4517896 3142376 0 0 229440 0 2912 2406 0 10 35 56
0 5 104 47408 4747272 2913156 0 0 229376 0 2903 2619 0 10 36 54
1 4 104 46800 4976648 2683560 0 0 229376 0 2726 2346 0 10 37 53
0 5 104 45284 5206024 2456248 0 0 229376 0 2856 2482 0 10 36 54
0 5 104 46524 5468168 2192136 0 0 262144 0 2956 2750 0 11 36 54
0 5 104 47284 5697544 1962556 0 0 229376 0 2894 2589 0 10 37 53
Takes awhile before it writes anything..
l1:/r# du -sb .
1250921771135 .
l1:/r# du -sb .
1250921771135 .
l1:/r# du -sb .
1250921771135 .
l1:/r# du -sb .
1250921771135 .
l1:/r# du -sb .
1250921771135 .
l1:/r# du -sb .
1250921771135 .
l1:/r# du -sb .
1250921771135 .
l1:/r# du -sb .
1250921771135 .
l1:/r# du -sb .
1250921771135 .
l1:/r# du -sb .
1250921771135 .
l1:/r# du -sb .
1250921771135 .
l1:/r#
.. 5 minutes later ..
l1:/r# du -sb .
1251764138111 .
l1:/r#
l1:/r# du -sb .
1251885887615 .
l1:/r#
l1:/r# ps auxww | grep dd
root 2206 4.5 0.0 10356 1672 ? D Dec02 11:46 dd if /dev/zero of 1.out bs 1M
root 2207 4.5 0.0 10356 1672 ? D Dec02 11:47 dd if /dev/zero of 2.out bs 1M
root 2208 4.4 0.0 10356 1676 ? D Dec02 11:42 dd if /dev/zero of 3.out bs 1M
root 2209 4.5 0.0 10356 1676 ? D Dec02 11:53 dd if /dev/zero of 4.out bs 1M
root 2210 4.4 0.0 10356 1672 ? D Dec02 11:43 dd if /dev/zero of 5.out bs 1M
root 2211 4.4 0.0 10356 1676 ? D Dec02 11:43 dd if /dev/zero of 6.out bs 1M
root 2212 4.4 0.0 10356 1676 ? D Dec02 11:38 dd if /dev/zero of 7.out bs 1M
root 2213 4.5 0.0 10356 1672 ? D Dec02 11:50 dd if /dev/zero of 8.out bs 1M
root 2214 4.5 0.0 10356 1672 ? D Dec02 11:47 dd if /dev/zero of 9.out bs 1M
root 2215 4.4 0.0 10356 1676 ? D Dec02 11:44 dd if /dev/zero of 10.out bs 1M
root 3251 25.0 0.0 10356 1676 pts/2 D 02:21 0:14 dd if /dev/md3 of /dev/null bs 1M
root 3282 0.0 0.0 5172 780 pts/2 S+ 02:22 0:00 grep dd
l1:/r#
HP raid controllers (CCISS) allow a pct(%) utilization for read/write,
does Linux/mdadm's implementation offer this anywhere in a sys or proc
tunable?
Justin.
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