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SubjectRe: Something wrong with scheduler in linux 2.1.127/2.1.128
"Michael H. Warfield" <mhw@wittsend.com> wrote:

> I think you are seeing what I've been seeing the the latest few revs.
> It takes a long time for this to get triggered so I've been very slowly doing
> a process of elimination to isolation when and where and how. It sometimes
> takes as much as a day before the things starts acting up for me.
>
> I see the same symptoms as you do but have been gathering other data.
> Seem that an active running process is ok but starting processes are a killer.
> Top shows 0% idle but 95% to 105% (yes greater than 100%) System time. User
> time is in low single digits. My first sign of trouble is a rapid rise in
> load average. This thing is normally getting triggered with something making
> a high file system demand (usually when I resync my mailbox in elm) and the
> load average takes a jump anyways. What happens in this case, though, is that
> the load average rises above the 1.0 - 1.5 I normally see and may peak out
> in 30-60 seconds at around 15 (NO THERE IS NO DECIMAL POINT IN THAT). Only
> choice I have then is to try and kill processes and try and reboot. Running
> processes seem almost impossible to kill, even though their CPU time is
> clocking up rapidly. With the high "system" percent, I would assume that
> they are all looping around down in the kernel.
>

I saw the same behavior with 2.1.128 on a UP Pentium 200 MMX with IDE, no
SCSI, and SMP disabled. I was compiling a large C++ file to local disk while
in X-windows. I could switch to the standard virtual consoles (and back to X)
but I could not start new processes. Alt-SysRq-T showed 5 or 6 processes running
continuously (stuck in 'R' state). When these programs compile, g++ grows to
about 70MB and I only have 64MB of memory so some swapping is occurring. Other
processes had been forked recently because one of the stuck running processes
was 'cron'.

I tried this once and then went back to 2.1.125 (which has been fine...).

I applied Alan Cox's 128ac2 patch last night and repeated the compilation
test which had previously failed one time. I left the machine looping,
rebuilding this particular program, all night.

It was still running after 8 hours this morning.


Perhaps some of the changes Alan made fixed this problem. I noted that one
of the changes was in fork() and its interactions with 'mm'.

-Ben McCann

--
Ben McCann Indus River Networks
31 Nagog Park
Acton, MA, 01720
email: bmccann@indusriver.com web: www.indusriver.com
phone: (978) 266-8140 fax: (978) 266-8111

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