Re: high system cpu load during intense disk i/o

Dimitrios Apostolou
2007-08-06T13:30:30Z

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Hello Andrew, thanks for your reply!

Andrew Morton wrote:
> On Sun, 5 Aug 2007 19:03:12 +0300 Dimitrios Apostolou <jimis@gmx.net> wrote:
>
>> was my report so complicated?
>
> We're bad.
>
> Seems that your context switch rate when running two instances of
> badblocks against two different disks went batshit insane. It doesn't
> happen here.
>
> Please capture the `vmstat 1' output while running the problematic
> workload.
>
> The oom-killing could have been unrelated to the CPU load problem. iirc
> badblocks uses a lot of memory, so it might have been genuine. Keep an eye
> on the /proc/meminfo output and send the kernel dmesg output from the
> oom-killing event.

Please see the attached files. Unfortunately I don't see any useful info
in them:
*_before: before running any badblocks process
*_while: while running badblocks process, but without any cron job
having kicked in
*_bad: 5 minutes later that some cron jobs kicked in

About the OOM killer, indeed I believe that it is unrelated. It started
killing after about 2 days, that hundreds of processes were stuck as
running and taking up memory, so I suppose the 256 MB RAM were truly
filled. I just mentioned it because its behaviour is completely
non-helpful. It doesn't touch the badblocks process, it rarely touches
the stuck as running cron jobs, but it kills other irrelevant processes.
If you still want the killing logs, tell me and I'll search for them.

Thanks,
Dimitris

[-- Attachment #2: meminfo_bad.txt --]
[-- Type: text/plain, Size: 728 bytes --]

MemTotal: 255912 kB
MemFree: 22928 kB
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Cached: 69168 kB
SwapCached: 0 kB
Active: 118440 kB
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SReclaimable: 18832 kB
SUnreclaim: 4960 kB
PageTables: 508 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
CommitLimit: 127956 kB
Committed_AS: 24928 kB
VmallocTotal: 770040 kB
VmallocUsed: 2852 kB
VmallocChunk: 766864 kB

[-- Attachment #3: meminfo_before.txt --]
[-- Type: text/plain, Size: 728 bytes --]

MemTotal: 255912 kB
MemFree: 26348 kB
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[-- Attachment #4: meminfo_while.txt --]
[-- Type: text/plain, Size: 728 bytes --]

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CommitLimit: 127956 kB
Committed_AS: 22060 kB
VmallocTotal: 770040 kB
VmallocUsed: 2852 kB
VmallocChunk: 766864 kB

[-- Attachment #5: vmstat_bad.txt --]
[-- Type: text/plain, Size: 936 bytes --]

procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
4 1 0 22688 123432 69172 0 0 7 78 45 21 3 0 96 1
4 2 0 22680 123432 69180 0 0 0 15872 249 461 34 66 0 0
4 2 0 22680 123432 69180 0 0 0 15872 247 468 37 63 0 0
4 2 0 22680 123432 69180 0 0 0 15872 251 472 38 62 0 0
4 2 0 22680 123432 69180 0 0 0 16000 252 495 43 57 0 0
4 2 0 22680 123432 69180 0 0 0 15872 252 471 32 68 0 0
3 2 0 22680 123440 69180 0 0 0 15984 251 516 73 27 0 0
3 1 0 22680 123440 69180 0 0 0 15872 250 482 33 67 0 0
4 2 0 22620 123440 69180 0 0 0 15872 251 467 30 70 0 0
4 2 0 22620 123440 69180 0 0 0 15872 250 460 45 55 0 0

[-- Attachment #6: vmstat_before.txt --]
[-- Type: text/plain, Size: 944 bytes --]

procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
0 0 0 26332 123196 68480 0 0 7 17 44 19 3 0 96 0
0 0 0 26324 123196 68484 0 0 0 0 45 16 0 0 100 0
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0 0 0 26324 123204 68484 0 0 0 0 29 16 0 0 100 0
0 0 0 26324 123204 68484 0 0 0 0 27 13 0 0 100 0
0 0 0 26324 123204 68484 0 0 0 0 13 14 0 0 100 0

[-- Attachment #7: vmstat_while.txt --]
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procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
2 2 0 25428 123288 69092 0 0 7 27 44 19 3 0 96 0
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2 2 0 25360 123292 69096 0 0 0 15872 283 442 0 2 0 98