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Re: Ksoftirq running wild .. What is it?



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On Tuesday 01 April 2003 23:17, Mariano Kamp wrote:
> Hi Nicolas,

> Oh really? Lol, ok I will take that into consideration in the future.
> To be serious again, what should I do in such a case? Reboot the machine
> would be the only other option I could think of and that reminds me too
> much of the other os.
> I've seen that a process id of "4" hints to an important system process
> and top also showed that the cpu was eaten up by a system process, so I
> understood that the process might be important, but I issued sync as a
> precaution and then tried to kill the process. Wouldn't that be enough
> precaution for most cases, I mean better than rebooting?

For when you're experimenting, yes, it should be.
I'm not sure that it actually works for journaling filesystems like ReiserFS 
or Ext3, though.

> Until kill -9 doesn't seem to take effect I believed in kill -9 as the
> last resort which will eventually kill a process. This doesn't seem to
> the case.

SIGKILL *cannot* be trapped by a process, and always terminates the process 
immediately.
However, there is one case where it doesnt't - when the process is currently 
running a syscall, or otherwise is in kernel context. Sometime syscalls take 
forever, which is annoying.

That said, kernel processes - generally anything with a really low PID and a 
name starting with 'k' - are always in kernel context. Thus, they cannot be 
killed, which is good since if they could be your system would execute HCF 
immediately.

> > >   Any idea what this process does?
> >
> > STFW. http://lwn.net/2001/0726/a/ugly.php3
> > In short: That is, as the name suggests, a kernel daemon handling soft
> > IRQs which hannot be handled at the spot.
>
> But something seems to flood my systems with "soft irqs".

Take a look at /proc/interrupts when that is happening. Under the CPU0 column, 
one number will be large - and probably increasing rapidly.

Take a note of which driver is responsible, which you can see to the right of 
it, and let us know. Oh, and you might want to unload said driver.

- -- 
Some people only open up to tell you that they're closed.
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