faster damage processing - bandwidth constraints handling

[Antoine Martin]

Follow up from #999. These classes are becoming complicated and slow.

TODO:

• run profiling again
• merge video source? (we never use window source on its own anyway)
• support multiple video regions?
• cythonize, use strongly typed and faster "deque":​Ring buffers in Python/Numpy
• pre-calculate more values: ECU "engine map" like
• more gradual refresh when under bandwidth constraints and at low quality: the jump from lossy to lossless can use up too much bandwidth, maybe refresh first at 80% before doing true lossless
• use more bandwidth? (macos client could use more quality?)
• slowly updating windows should be penalized less
• don't queue more frames for encoding after a congestion event (ok already?)
• maybe keep track of the refresh compressed size?

See also #920: some things could be made faster on the GPU..

[Antoine Martin]

See also #1761

[Antoine Martin]

See also ticket:1769#comment:1 : maybe we should round up all screen updates to ensure we can always use color subsampling and video encoders? Or only past a certain size to limit the cost?

[Antoine Martin]

profiling encoding selection

[Antoine Martin]

After much profiling, it turns out that encoding selection is actually pretty fast already:

And so we're better off spending extra time choosing the correct encoding, instead of trying to save time there: r18669.
Other micro improvements: r18667, r18668

See also ticket:1299#comment:6, we seem to be processing the damage events fast enough (~0.25ms for do_damage), but maybe we're scheduling things too slowly when we get those damage storms?

[Antoine Martin]

For the record, I've used this command to generate the call graphs:

python2 ./tests/scripts/pycallgraph -i damage -- start --start-child="xterm -ls" --no-daemon

Minor related fix: r18685.

Re-scheduling as the profiling has shown that this is not a huge overhead after all.

[Antoine Martin]

Milestone renamed

[migration script]

this ticket has been moved to: ​https://github.com/Xpra-org/xpra/issues/1700