[PD] Gem on Raspberry pi 2
glitchpop at gmail.com
Mon Mar 16 02:09:31 CET 2015
Disappointing but good on you for trying it out... hopefully an open
accessible openGL capable embedded platform soon...?
On Sun, Mar 15, 2015 at 8:47 PM, Cyrille Henry <ch at chnry.net> wrote:
> Le 15/03/2015 04:11, Simon Wise a écrit :
> Apparently there is some support beyond Es, but not enough to run gem
>> and as not at all documented.
> i was to much optimistic and did not double check the informations i found
> announcing openGL support.
> thanks for the clarification.
>> If you are experimenting with an RPi 2 then with audio the load balancing
>> by switching cores will add considerable latency (X-runs at latencies the
>> RPi 1 handles fine). This is probably due to cache invalidation on a core
>> switch, and the time required to fetch everything again if the switch
>> occurs at an inopportune moment re buffers and deadlines. For low latency
>> audio you will need to use linux cpu affinity to always put the main pd
>> process on a specific core, this can also be achieved by the no-sleep flag
>> in pd which sets pd to use busy-waiting (I believe) so run continuously and
>> fully occupy one core. There may be advantages to either technique, no
>> point sleeping a process if it owns the core exclusively, but running 100%
>> may also lead to heating issues and a need to run at lower clock speeds...
>> depending I guess on how the no-sleep is implemented.
>> This could prove useful if you are ready to manually split your
>> processing between separate pd patches and script the launching to achieve
>> the cpu affinity required. cpusets could help more, making a core (or
>> three) dedicated exclusively to a pd process each while the remaining
>> core(s) run anything else.
>> Some have said there may be heating issues without load balancing, but
>> the devices are cheap so a shortened life probably isn't an issue, other
>> heat problems could arise ... maybe slow down the clock speed or add a
>> decent heat sink to the chip if you are playing with this option.
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