[PATCH 4/4] arm: Support VFP-D32 and Neon

[Gedare Bloom]

On Fri, May 10, 2013 at 3:46 AM, Sebastian Huber
<sebastian.huber at embedded-brains.de> wrote:
> On 05/08/2013 07:39 PM, Claus, Ric wrote:
>>
>> Do all tasks pay the cost of context switching the FP context in this
>> scheme, or just those tasks that are marked FP?  If there is only one FP
>> task and many non-FP tasks in the system, is the FP context ever switched?
>
>
> All tasks and interrupts can use floating point operations.  The thread
> switch overhead is not that high (64 bytes to save/restore).  The interrupt
> entry and exit latency might be noticeable (196 bytes to save/restore).
> Everything has its price.  In theory it is possible to implement a lazy
> floating point context switching, but this is quite complex and I don't have
> the resources to implement it.
>
This is architecture-dependent. grep for CPU_USE_DEFERRED_FP_SWITCH in
cpukit/score/cpu and you can see which architectures support FP
context switches only for FP tasks.

>
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