Input latency

Daniel van Vugt daniel.van.vugt at
Mon Dec 16 08:40:36 UTC 2013

Nexus10 (3.4.0-4-manta)
Direct 1.0ms with sporadic spikes to 74ms, sometimes 400ms
Nested 1.2ms with sporadic spikes to 100ms, sometimes 1000ms

I'm not convinced the problem is specifically Android. It could just be 
a common issue visible on the slowest hardware.

On the Nexus10, just running a single server and client (egltriangle) 
occupies almost 100% of one of the cores. So stressing the CPU doesn't 
leave much time for being responsive.

On 13/12/13 17:31, Daniel van Vugt wrote:
> Here are some fun numbers I've collected about the latency between input
> events sent from the top-level Mir server to a client. All in
> milliseconds...
> Desktop (3.12.0-7-generic)
> Direct 0.8ms
> Nested 1.3ms
> Desktop (3.11.0-11-lowlatency)
> Direct 1.0ms
> Nested 1.7ms
> Nexus4 (3.4.0-3-mako)
> Direct 0.9ms
> Nested 1.5ms with high variance; frequent spikes to 73ms. Sometimes 700ms.
> The above numbers are for motion events. Key events appear to be twice
> as fast (half the latency). This suggests we could yet optimize the
> processing of motion events to perform better like key events do.
> In summary, we're looking pretty good. Only the Nexus has potential
> usability issues, and even then, only with nested servers.
> - Daniel

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