Re: ksoftirqd uses 99% CPU triggered by network traffic (maybeRLT-8139 related)

[Pasi Sjoholm]

On Wed, 28 Jul 2004, Robert Olsson wrote:

>> It would be nice that one could use the full capacity of his/her computer.
>> This is not a big problem for everyday use for a workstation but prevents 
>> 2.6-series to be used in production-enviroments in the servers.
>> But hey.. we need to do some work and maybe we will resolve this. =)
> this now. But it does not address userland starvation so if you your workload 
> can give reproduceably results wrt starvation (Alexey's app) we can do some
> tests. First I think should be collect data from current system and check 
> that results a reproduceable. 

It takes about 2 minutes to reproduce the symptoms so it's not a problem 
anymore when I know exactly what I have to do.
 
> Below is a patch to monitor softirq's it uses fastroute stats in softnet_stat
> you may have to hack it.

Ok, I had to do some modifications but here are the results:

while true; cat /proc/net/softnet_stat | tee -a log.txt; sleep 5; done

The first log is when running exact same patch you sent.

--
000401f1 00000000 00000000 00000000 000002ec 000000d8 00084026
0004495c 00000000 00000000 00000000 00000326 000000d8 0008ae93
0004820b 00000000 00000000 00000000 0000034a 000000d8 00090755
0004a613 00000000 00000000 00000000 00000358 000000d8 00093f0f
0004ca12 00000000 00000000 00000000 00000370 000000da 000976c9
000500f2 00000000 00000000 00000000 0000045e 000000da 0009cf4b
0005417b 00000000 00000000 00000000 000005f8 000000da 000a36b5
00056a66 00000000 00000000 00000000 0000064c 000000da 000a7619
0005a94b 00000000 00000000 00000000 000007bf 000000da 000ad9da
0005d9b7 00000000 00000000 00000000 00000816 000000db 000b1fff
00060286 00000000 00000000 00000000 00000834 000000db 000b5dee
00064ffb 00000000 00000000 00000000 00000a0c 000000db 000bd33c
00069498 00000000 00000000 00000000 00000b97 000000db 000c3d62
0006cdf1 00000000 00000000 00000000 00000cc5 000000db 000c972b
0006f9cc 00000000 00000000 00000000 00000d43 000000db 000cde12
0007280d 00000000 00000000 00000000 00000dea 000000db 000d268d
00074f33 00000000 00000000 00000000 00000e3e 000000db 000d655b
00078271 00000000 00000000 00000000 00000f45 000000db 000db849
0007beee 00000000 00000000 00000000 0000106e 000000db 000e18ae
0007e402 00000000 00000000 00000000 00001086 000000db 000e513b
000815c4 00000000 00000000 00000000 0000114d 000000db 000e9d33
00082abc 00000000 0000076c 00000000 000011f0 000001ad 000ec552
00082abc 00000000 00001180 00000000 000014e8 00000207 000ecc14
00082abc 00000000 00001b44 00000000 000014e8 00000257 000ed588
00082abc 00000000 0000251c 00000000 000018bc 000002bb 000edb28
00082abc 00000000 00002ee0 00000000 00001970 0000033d 000ee3b6
00082abc 00000000 000038e0 00000000 00001eac 0000038d 000ee82a
00082abc 00000000 0000443e 00000000 00002244 00000405 000eef78
00082abc 00000000 00004e02 00000000 000024c4 00000469 000ef658
00082abc 00000000 000057c6 00000000 000026cc 000004c3 000efdba
00082abc 00000000 000061da 00000000 00002910 00000513 000f053a
00082abc 00000000 00006bbc 00000000 00002b2c 0000056d 000f0ca6
00082abe 00000000 000075c6 00000000 00002e10 000005d1 000f1368
00082abe 00000000 00007f9e 00000000 000030a4 00000635 000f1a48
00082abe 00000000 000089da 00000000 00003338 000006a3 000f2182
00082abe 00000000 00009420 00000000 00003554 000006fd 000f2952
00082abe 00000000 00009e70 00000000 00003c34 00000829 000f2b96
00082ac0 00000000 0000a8c0 00000000 000044cc 00000991 000f2be6
00082ac0 00000000 0000b2e8 00000000 00004814 00000fd1 000f2c86
00082ac0 00000000 0000bcfc 00000000 00004814 0000199f 000f2ccc
00082ac0 00000000 0000c72e 00000000 00004814 00002377 000f2d26
00082ac2 00000000 0000d142 00000000 00004864 00002c19 000f2e48
00082ac2 00000000 0000db56 00000000 00004864 0000358d 000f2ee8
00082ac2 00000000 0000e574 00000000 00004864 00003f33 000f2f60
00082ac2 00000000 0000ef9c 00000000 0000497c 000047e9 000f2fba
00082ac2 00000000 0000f9b0 00000000 0000497c 000051ad 000f300a
00082ac2 00000000 000103ce 00000000 0000497c 00005b7b 000f305a
00082ac4 00000000 00010dec 00000000 0000497c 00006549 000f30aa
00082ac4 00000000 0001180a 00000000 0000497c 00006f17 000f30fa
00082ac4 00000000 0001225a 00000000 00004a94 00007809 000f3140
--

and the second one is when that if-condition is true (just wanted to try 
if that would make any difference):

#if 1
        /* Avoid softirq's from DoS'ing user apps incl. RCU's etc */

--
00000082 00000000 00000000 00000000 00000010 00000116 0001fe40
00000082 00000000 00000000 00000000 00000010 00000119 000211f9
0000094d 00000000 00000000 00000000 00000014 0000011b 00022e69
00004ab8 00000000 00000000 00000000 00000032 0000011d 0002877e
00006b19 00000000 00000000 00000000 0000003f 0000011f 0002cb8e
0000c7a0 00000000 00000000 00000000 00000073 00000122 0003409e
0001334a 00000000 00000000 00000000 000000d6 00000124 0003dd4e
00017537 00000000 00000000 00000000 00000113 00000127 00044598
0001b528 00000000 00000000 00000000 0000015a 00000129 0004acb5
0001ec8f 00000000 00000000 00000000 000001ae 0000012b 0005024a
00021186 00000000 00000000 00000000 000001c1 0000012e 00053ace
000236f1 00000000 00000000 00000000 00000205 0000012e 000575c7
00026980 00000000 00000000 00000000 0000032b 0000012e 0005c601
0002a70a 00000000 00000000 00000000 000004aa 0000012e 0006258f
0002e715 00000000 00000000 00000000 00000664 0000012e 00068ddc
00030c8b 00000000 00000000 00000000 00000690 0000012e 0006c872
0003303e 00000000 00000000 00000000 000006a3 0000012e 0006ffc6
00036172 00000000 00000000 00000000 00000786 0000012e 00074e6d
0003a3c8 00000000 00000000 00000000 0000096a 0000012e 0007b998
0003d62b 00000000 00000000 00000000 00000a85 0000012e 000808b0
000401ab 00000000 00000000 00000000 00000aa4 0000012e 000847bf
000426ba 00000000 00000000 00000000 00000ab5 0000012e 0008807b
00046099 00000000 00000000 00000000 00000c57 0000012e 0008dd31
0004a27a 00000000 00000000 00000000 00000e0b 0000012e 00094686
0004c2dc 00000000 00000122 00000000 00000e2c 000001b0 000979c8
0004c2dc 00000000 00000bae 00000000 00000e2c 00000228 000983dc
0004c2dc 00000000 00001568 00000000 00001084 00000282 00098ae4
0004c2dc 00000000 00001f0e 00000000 00001084 000002f0 0009941c
0004c2dc 00000000 00002968 00000000 00001084 00000368 00099dfe
0004c2dc 00000000 00003354 00000000 00001426 000003ae 0009a402
0004c2dc 00000000 00003d04 00000000 0000150c 0000041c 0009ac5e
0004c2dc 00000000 00004790 00000000 00001548 00000494 0009b636
0004c2dc 00000000 00005140 00000000 00001548 00000502 0009bf78
0004c2de 00000000 00005b68 00000000 00001548 0000057a 0009c928
0004c2e0 00000000 000065ae 00000000 00001598 000005e8 0009d2b0
0004c2e2 00000000 00006f4a 00000000 00001598 00000660 0009dbd4
0004c2e2 00000000 000079a4 00000000 00001660 000006ce 0009e4f8
0004c2e2 00000000 000083d6 00000000 00001660 00000746 0009eeb2
0004c2e2 00000000 00008e08 00000000 00001764 000007b4 0009f772
0004c2ee 00000000 00009858 00000000 00001764 0000082c 000a014a
0004c2f6 00000000 0000a1fe 00000000 00001764 0000089a 000a0a82
0004c2fc 00000000 0000abcc 00000000 0000182c 000008f4 000a132e
0004c2fc 00000000 0000b626 00000000 0000182c 000011aa 000a14d2
0004c302 00000000 0000c03a 00000000 00001872 00001aec 000a155e
--

and it did not make any difference. I have cut out the output of "cat 
softnet_stat to show columns from 1 to 7. 

- When the ksoftirqd starts to eat cpu-time time_squeeze-value (3rd 
column) starts growing (in both cases it's same thing). 

- We are also getting more hits from SIRQ_FROM_KSOFTIRQD 
immediately after that. (6th column)

- Total-column's value stops growing although network file transfers 
are still on. (1st column)
 
> And maybe we should take the experiment disussions off the list.

I think that we should leave netdev as Francois requested it in first 
place but we can drop the lkml if you want to.

--
Pasi Sjöholm



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