[PD] Gem on Raspberry pi 2

Cyrille Henry ch at chnry.net
Sun Mar 15 10:47:02 CET 2015

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.
> Simon
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