2 Jun
2004
2 Jun
'04
7:41 p.m.
On Wednesday 02 June 2004 22.13, Michael Ost wrote:
What specific benefits have folks seen by turning on
the kernel
preemption patch in a 2.4.19 kernel?
2.4 series is not really built for preemption. But...
We found that a nasty system crash was fixed by turning off preemption.
The crash would happen fairly reliably by switching between virtual
terminals a number of times. It locked up the system hard. So hard that
we can't really find the problem in the kernel; we just found a
work-around basically by trial and error.
Do you use a SMP computer? If not then you might have run into something
that could hurt a SMP computer running without preemption...
(Running SMP and preemption is kind of weird. And you may run into additional
problems - per CPU data has also to be protected by spinlocks, etc... )
We turned on kernel preemption basically because "everyone was doing
it". We haven't noticed any obvious, serious problems or differences
since turning preemption off.
Does anyone have some suggestions about what differences to expect and
what we might have a closer look at?
You won't notice much difference unless you run real time processes. But they
will need to be suid root (or some wrapper/helper) to become RT processes,
and many kernels do not ship with multimedia stuff suid...
Also, we are newbies about reporting this kind of crash. Any clues about
where to report it or ask about it?
First - you mention virtual terminals
What video driver are you using? Nvidia?
If that is the case retest with xfree86 (nv)
Second - try to what is happening (Magic SysRq)
Third - 2.4.19 is kind of old now (not that many will be interested...),
upgrade and try to reproduce.
/RogerL
--
Roger Larsson
Skellefteå
Sweden