Re: [gentoo-amd64] Re: Identifying CPUs in the kernel

[Peter Humphrey]

On Saturday 23 June 2007 10:52:33 Duncan wrote:
> Peter Humphrey <prh@××××××××××.uk> posted
> > top - 09:04:59 up 23 min, 5 users, load average: 3.60, 4.79, 3.91
> > Tasks: 124 total, 2 running, 122 sleeping, 0 stopped, 0 zombie
> >
> > Cpu0: 0.3%us, 0.3%sy,  0.0%ni, 99.3%id, [zeroes]
> > Cpu1: 0.0%us, 0.3%sy, 99.7%ni,  0.0%id, [zeroes]
> >
> > PID USER  PR NI S %CPU %MEM  TIME+   P COMMAND
> > 5279 prh  34 19 S   50  1.0  6:53.97 1 setiathome-5.12
> > 5280 prh  34 19 S   50  1.0  6:54.08 0 setiathome-5.12
> >
> > I don't think this is a scheduling problem; it goes deeper, so that the
> > kernel doesn't have a consistent picture of which processor is which.
>
> Critical question here, is that in SMP Irix or SMP Solaris mode?  (See
> the top manpage if you don't know what I mean.)  Asked another way, is
> that displaying percent of total CPU time (both CPUs) or percent of
> total divided by number of CPUs (so percent of one CPU)?

That's another oddity. I press <I> (capital letter i) and /top/ says "Irix 
mode off" and shows half the previous percentage CPU in the process lines: 
25 in the example above. I then press <I> again and it says "Irix mode on" 
and shows the 50s again. Is this backwards, or is my utter confusion 
showing?  :-(

I want it to show:
  -	for each CPU, the percent to which it is loaded; and,
  -	for each process, how much of a CPU's time it is consuming.
The presence of two CPUs requires two CPU lines and allows for two lots of 
processes. That seems logical to me. Is it Irix mode or Solaris?

This morning /top/ is showing this:
--- 
top - 10:51:55 up  2:22,  5 users,  load average: 2.43, 2.34, 2.60
Tasks: 121 total,   4 running, 117 sleeping,   0 stopped,   0 zombie
Cpu0  :  0.3%us,  0.3%sy,  0.0%ni, 99.3%id,  [zeroes]
Cpu1  :  0.0%us,  0.3%sy, 99.7%ni,  0.0%id,  [zeroes]

PID USER      PR  NI  S %CPU %MEM    TIME+  P COMMAND
5270 prh      34  19  S   50  0.9  67:55.08 1 setiathome-5.12
5271 prh      34  19  S   50  1.1  67:57.80 1 einstein_S5R2_4
--- 

So CPU1 is fully loaded and CPU0 is idling. Gkrellm shows the same. The box 
has been running for 2 hours from cold and I haven't tampered with 
anything; BOINC starts from /etc/init.d/local. When /top/ is behaving this 
way my problem seems to be one of scheduling, but I'm pretty sure it isn't.

> I'm not sure where your bug is, but [...] the problem appears to be way
> deeper than scheduling.  I'd guess it's ultimately a kernel bug, possibly
> due to a hardware bug

That's my thought too.

> [...] you might wish to file it on top initially, just to see if they've
> seen [anything] similar and can tell you what's going on.  Unless you want
> to double-check patching status yourself, you might as well file the bug
> with Gentoo first, in case it's a Gentoo bug.  They'll probably end up
> closing it "upstream", but at least then when you file it upstream, you
> can say you've cleared it with Gentoo first.

I'll do that, but I'll wait a day or two to see what else comes up here.

> You definitely have a strange one here, and I'd /love/ to see what the
> real experts have to say about it!

Mm, me too.

-- 
Rgds
Peter Humphrey
Linux Counter 5290, Aug 93
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