[uClinux-dev] Excluding one of n Cores
mschnell at lumino.de
Tue Jul 30 06:57:15 EDT 2013
On 07/30/2013 12:22 PM, Paul Chavent wrote:
> I'm not an expert. But i give you my ("standard" linux kernel) point
> of view (don't know if it works with uClinux).
GREAT ! As I have Debian or something similar in mind, this might not
really be "uCLinux", anyway. :-)
In fact, is "uClinux" still defined as noMMU ? I understand that
regarding the great success of ARM Cortex A8+ chips noMMU is more and
more obsolete an "uClinux" might get a synonym for "small embedded",
with "small" now going up to "1GHz 1GByte".
> See the isolcpu kernel parameter.
I'll take a look.
> Something like interrupt balancing ?
I am not sure how SMP hardware usually is done. I understand that when a
hardware interrupt happens, exactly one of the cores gets the interrupt
and starts the ISR. But which one ? Is the assignment "Interrupting
hardware -> Core Number" fix ? Is it programmable at system start ? Is
it done dynamically e.g. according to the performance done by the
Kernels (i.e. a rather idle Kernel gets interrupted). Is there hardware
support for this ?
When doing AMP with such SMP-enable hardware, some interrupts need to be
fixed assigned to the "special purpose" core to trigger the appropriate
low latency actions there.
> I never tried to enable mmu with uclinux. But on a "standard" linux i
> use mlock to deal with mmu, caches etc.
(I just don't know where to ask embedded "non uCLinux" questions, so I
thought here would be the best place for strictly embedded Linux
questions, even with MMU involved.)
Thanks a lot !
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