[Xenomai] imx6q xenomai ipipe-3.0-imx6q

Gilles Chanteperdrix gilles.chanteperdrix at xenomai.org
Sun Apr 20 11:23:19 CEST 2014


Le 20/04/2014 11:03, Gilles Chanteperdrix a écrit :
> Le 20/04/2014 07:06, eric a écrit :
>> So if my program use lots of memory operations  for a long time it maybe
>> gives non real-time activities opportunity to thrash the cache?
> 
> It is unrelated, but on a multi-core processor even when one core is
> running a real-time task, other cores can thrash the cache at will, or
> slow down the real-time task by using a shared ressource (for instance
> DDR) and starving the core where the real-time task runs. By default the
> L2 cache is shared between all cores, you can try and reserve parts of
> the cache for each core (check the l2x0 registers documentation to see
> how), I tried this on omap4, but it results on worse latencies,
> situation may be different on imx6 though. Another problem is that since
> the L1 cache is per-core, I believe, and we disable L2 write allocate,
> reading on one core memory written on another core results in accesses
> at the DDR speed, and not at the cache speed.
> 
> All this to say that Xenomai focuses on trying to schedule your driver
> interrupts and application threads in a deterministic fashion but it is
> your job to make sure that these interrupts and threads do not take too
> long a time to execute, because if they do, yes, your application will
> not meet its deadlines, but it is not Xenomai's fault.

I do not mean to say that you do not have a problem with Xenomai on
imx6q, but so far, I have not understood what this problem was.


-- 
Gilles.




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