Hello,
Apologies in advance if Red Hat kernels should not be discussed
here (pointers are appreciated).
I've recently upgraded to kernel-2.4.18-17.7.x.athlon.rpm (from
kernel-2.4.18-10.athlon.rpm) and I've noticed a problem with the
CPU idle %. Here is an example of what happens when running
"top":
10:37am up 8 days, 22:02, 9 users, load average: 1.00, 1.01, 1.00
89 processes: 81 sleeping, 7 running, 1 zombie, 0 stopped
CPU states: 0.1% user, 0.1% system, 99.8% nice, 857278.7% idle
Mem: 514156K av, 485724K used, 28432K free, 0K shrd, 57956K buff
Swap: 522072K av, 44048K used, 478024K free 288448K cached
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME COMMAND
18840 mersenne 39 19 14996 14M 696 R N 99.9 2.9 7046m mprime
14091 marco 15 0 1084 1084 848 R 0.1 0.2 0:00 top
1 root 15 0 472 444 420 S 0.0 0.0 0:04 init
2 root 15 0 0 0 0 SW 0.0 0.0 0:01 keventd
3 root 15 0 0 0 0 SW 0.0 0.0 0:00 kapmd
As you can see the idle value is absurd (it blows up about 1 in five
times, other updates are reasonable e.g. 0.2% idle). When running "top"
the value consistently jumps to about 800000% about 20% of the time.
If I run "top -d1" so that the updates take place every second the
value consistently jumps to about 4200000%, again about 20% of the time.
Running "top -d2" makes it jump to around 2000000%. The idle value
behaves approximately as follows:
4200000
idle = --------% once every five updates.
interval
If I stop "mprime" so that the system load becomes negligible the
idle value does not spike. If I run "mprime" or any other CPU-consuming
task (e.g. yes > dev/null) the spikes commence. The niceness of
the process does not seem to matter.
My hardware is an Athlon 2100+ running on an ASUS A7V333.
> uname -a
Linux reimeika.math.toronto.edu 2.4.18-17.7.x #1
Tue Oct 8 11:49:30 EDT 2002 i686 unknown
> top --version
top (procps version 2.0.7)
I should note that all previous Red Hat 7.3 kernels ran fine.
It's telling that according to the 2.4.18-17.7.x errata at:
http://rhn.redhat.com/errata/RHSA-2002-206.html
it's mentioned that the following bug:
/proc/uptime shows wrong uptime (slightly) and idle time (totally)
( http://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=75113 )
has been fixed.
Kernel bug? "top" bug? Something else? Suggestions appreciated.
Please CC responses to my "Reply-To:" if possible.
Cheers,
--
[email protected]
Gunnm: Broken Angel
http://reimeika.ca/
On Wed, 2002-10-30 at 20:58, marco wrote:
> Hello,
>
> Apologies in advance if Red Hat kernels should not be discussed
> here (pointers are appreciated).
That doesnt sound like one I've seen outside of the RH kernel so please
do file it in https://bugzilla.redhat.com/bugzilla.
On Wed, 30 Oct 2002, marco wrote:
> Apologies in advance if Red Hat kernels should not be discussed
> here (pointers are appreciated).
> CPU states: 0.1% user, 0.1% system, 99.8% nice, 857278.7% idle
Idle time in the kernel can go backwards (due to a silly calculation)
and this can make the time in top overflow.
I think Red Hat has a patch in their procps rpm to catch this, but
I guess that one only catches negative overflow ;)
regards,
Rik
--
Bravely reimplemented by the knights who say "NIH".
http://www.surriel.com/ http://distro.conectiva.com/
Current spamtrap: <a href=mailto:"[email protected]">[email protected]</a>
Hello,
Thank you for your responses. In answer to your question
Dmitri, I got the kernel from updates.redhat.com and
verified the GPG signature. This bug was actually
submitted to Red Hat's bugzilla on October 26 (# 76797).
I've added my experience to that report.
Thanks again to Dmitri, Alan and Rik. Just seeing these
names made me giddy :)
Cheers,
--
[email protected]
Gunnm: Broken Angel
http://reimeika.ca/