[Bdi4emc-help] Quickstep driver
matt at timmermans.org
Mon Feb 13 05:47:37 CET 2006
Yes, it's still all real-time.
To measure CPU usage, I just ran bogomips in user space. This tells me how
much CPU is left over after all the higher priority tasks take their cut.
If M is the score when the system is unloaded, or reported during boot, and
m is the score when EMC is up and doing a rapid move, I know that the
fraction of CPU consumed by the real-time tasks is <= (M-m)/M.
Uncertainty remains about just how fast you can go, however, because
quickstep's critical work isn't quite evenly distributed across PERIODs. I
don't think it's too far off, though. On a slower machine, I guess that
it's probably safe to decrease PERIOD until the real-time work eats up half
the CPU. A really fast machine may hit some limit in the capabilities of
the interrupt hardware first.
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