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SubjectRE: 2.4.1 under heavy network load - more info
Date


> In that case, could I see some vmstat (and/or top) output of
> when the kernel is no longer able to keep up, or maybe even
> a way I could reproduce these things at the office ?

Interactive response is actually pretty OK, the only thing I'm seeing is
short (about 1 sec) pauses, they could be due to network problems or VM
stuff...
hard to say because I work with the machine over the net and not from
console.
What I do see during these short pauses is that sendq is building up on the
remote end, nothing happens for a short while and then things continue as
nothing bad happened ;)

It feels like a subtle problem, nothing terribly wrong, but the system does
not feel
100% OK either. Be it a networking or a VM-problem.

Some data from vmstat
root@mcquack:/root# vmstat 3
procs memory swap io system
cpu
r b w swpd free buff cache si so bi bo in cs us sy
id
1 0 0 76572 2400 324 48160 4 2 1 1 22 14 47 39
14
1 0 0 76572 2400 324 48160 0 0 0 1 3889 5 49 51
0
1 0 0 76572 2400 324 48160 0 0 0 1 3698 7 48 52
0
1 0 0 76572 2400 324 48160 0 0 0 0 3759 6 46 54
0
1 0 0 76572 2400 324 48160 0 0 0 0 2987 6 48 52
1
1 0 0 76572 2400 324 48160 0 0 0 0 3015 5 46 54
0
1 0 0 76572 2400 324 48160 0 0 0 0 4024 4 45 55
0
2 0 0 76572 2396 324 48160 0 0 0 0 4066 21 44 42
14
1 0 0 76572 2400 324 48160 0 0 0 0 3995 75 29 26
44
1 0 0 76572 2400 324 48160 0 0 0 0 3747 30 43 40
16
1 0 0 76572 2400 324 48160 0 0 0 0 3568 5 44 56
0
1 0 0 76572 2400 324 48160 0 0 0 0 3942 4 43 57
0
1 0 0 76572 2400 324 48160 0 0 0 0 3702 5 44 56
0
1 0 0 76572 2376 320 48176 0 0 0 0 3994 50 33 32
34
1 0 0 76572 2376 320 48176 0 0 0 0 3637 31 25 24
51
1 0 0 76572 2376 320 48176 0 0 0 0 3445 5 48 52
0
1 0 0 76572 2376 320 48176 0 0 0 0 3709 5 52 48
0

This goes on and on, long periods of zero idle time and then a short period
with some idle time and some more cs, the "short pauses" are (when they
happen to occur) just before or slightly after the period with more context
switches.

Top says:
4:53pm up 5 days, 13:42, 1 user, load average: 0.62, 0.69, 0.64
22 processes: 19 sleeping, 3 running, 0 zombie, 0 stopped
CPU states: 47.1% user, 52.8% system, 0.0% nice, 0.0% idle
Mem: 127264K av, 125052K used, 2212K free, 0K shrd, 452K
buff
Swap: 499960K av, 76680K used, 423280K free 48480K
cached

PID USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME COMMAND
1152 adm 20 0 110M 78M 42792 R 0 99.3 63.1 6772m ircd


Btw..the box is a PII-450 so it's not terribly slow ;)


> I'm really interested in things which make Linux 2.4 break
> performance-wise since I'd like to have them fixed before the
> distributions start shipping 2.4 as default.


As always, I'm happy to provide you with more information if I can!

Regards,
Magnus

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