Girish Kale wrote:
Hi,
I have a few basic questions on the kernel performance:
1) For embedded systems, even though standard linux may not have hard
real-time performance unless real-time patch, low latency patch are
applied, I would like to know if linux can give "deterministic"
performance. Meaning can we be guaranteed that a particular process will
be scheduled after a particular time. What are the these times or where
do I find this data.
You can only get "deterministic" performance if you're using a real-time
patch. I'm not sure what the timing is, but I believe that it's in the
sub-milisecond range.
You might be able to get near-realtime (but no absolute guarantees)
by setting the process that needs fast response to nice -20 this
gives it highest priority, so that it gets CPU pretty much whenever
it wants it (after device drivers).
2) When we are using linux on an embedded system, will there a memory
management unit for this, since there will not be any swapping in/out of
pages? Can we avoid a process from keeping on allocating memory thereby
starving other applications?
Linux generally wants an MMU. Embeded kernels MAY be able to
survive without one (dunno).
Check the setrlimit call, or the ulimit bash built=in for info on
how to set resource usage limits.
You can also set limits on a system-wide basis by using the /proc mechanisms.
(your system probably has a formalized way of doing that automatically on boot..
for RedHat, that would be the file /etc/sysctl.conf )
--
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