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SubjectRe: Linux 2.4.20-SMP: where is all my CPU time going?
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> > I have been running Linux-2.4.20-SMP on my dual PIII-9333MHz machine
> > (1 GB RAM) for over 3 weeks as a desktop machine, with 2 instances of
> > SETI@Home running at nice 19 in the background the whole time:
>
> but other unknown factors have changed, right? like daily use
> of the desktop?

Yes, I do *use* my destop occasionally... ;-). However, my full "SETI
statistics" file contains daily data going back to October 2000. For
example, here is a excerpt from September 2002:

TIMESTAMP [2002] CLIENT NAME RUN-TIME SYS-TIME
Sep 22 23:08:00: SETI-5 20606.560000 190.480000
Sep 23 02:19:22: SETI-1 31343.990000 289.770000
Sep 23 08:47:07: SETI-2 32592.250000 273.890000
Sep 23 11:19:43: SETI-3 30795.910000 265.160000
Sep 23 18:10:38: SETI-4 32877.130000 270.660000
Sep 23 20:11:08: SETI-6 30946.050000 265.570000
Sep 24 03:51:53: SETI-5 33192.640000 270.920000
Sep 24 05:53:52: SETI-1 33039.560000 279.380000
Sep 24 13:32:49: SETI-2 32785.650000 271.290000
Sep 24 15:38:35: SETI-3 33046.460000 282.480000
Sep 24 23:16:30: SETI-4 32947.420000 279.430000
Sep 25 00:12:22: SETI-6 28678.120000 259.580000
Sep 25 07:52:13: SETI-5 28920.640000 268.700000
Sep 25 10:57:25: SETI-1 33598.060000 554.140000
Sep 25 22:24:01: SETI-3 16284.640000 2286.710000
Sep 26 00:34:02: SETI-2 31303.880000 2678.700000
Sep 26 08:17:12: SETI-6 33268.100000 281.640000
Sep 26 09:52:11: SETI-5 31248.750000 276.190000
Sep 26 18:00:18: SETI-1 32560.010000 274.440000
Sep 26 19:08:24: SETI-3 31045.920000 269.040000
Sep 27 03:54:47: SETI-2 33266.910000 276.200000
Sep 27 04:46:27: SETI-4 32386.510000 272.180000
Sep 27 13:27:50: SETI-6 33058.870000 267.090000
Sep 27 14:21:14: SETI-5 33171.320000 271.520000
Sep 27 21:45:00: SETI-1 28743.730000 251.880000
Sep 27 23:59:34: SETI-3 33474.890000 261.430000
Sep 28 07:17:16: SETI-2 33210.900000 256.300000

I have not changed the way I have used this machine, and yet these
"sys-spikes" only appear for two work units. This box should also not
suffer from memory starvation:

$ free -t
total used free shared buffers cached
Mem: 1033532 839516 194016 0 57468 596040
-/+ buffers/cache: 186008 847524
Swap: 498004 12000 486004
Total: 1531536 851516 680020

> > Feb 07 18:20:19: SETI-1 33722.820000 203.570000
> > Feb 09 06:14:08: SETI-1 33391.280000 2165.590000
>
> do you have any other data? if the kernel happens to pull pages away
> from the seti process, it could easily cause this sort of thing.

Well, I actually have no idea what sort of activity counts towards the
sys-time total. Is this time spent in spinlocks? Semaphores? Waiting
for DMA transfers to complete? And we're talking 36 minutes-worth of
sys-time here! It sounds as if some in-kernel process is going
completely off the deep end.

> check your cron jobs; I'm guessing you simply run updatedb or something
> at that interval. it does enough IO to flush pages in the seti client's
> working set.

My only cron job is one that runs "rmmod -a" every hour.

> that's just one possible perturber, though: there are plenty of other
> mechanisms that would work fine to produce this kind of effect.
> some sort of cache-thrashing in particular.

Could cache-thrashing account for the 9 hours of missing run-time? I
didn't see or hear any unusual disc activity last night, and the only
processes in my run-queue were the two setiathome ones.

Chris
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