VSE cache processing was handling thumbnail generation requests in
parallel, however often that was resulting in CPU core over-subscription
that negatively affects user interface smoothness. Process requests
serially; some parts of image/video loading are internally multi-threaded
already. This makes thumbnails load somewhat slower, but while that
is happening the rest of blender feels much smoother, and the CPU
fans don't spin up as much.
Additionally, make the video thumbnail loading code use smallest
available proxy file, if present. This was overlooked in the original
new thumb cache implementation (!126405).
SpriteFright timeline edit v135 (mostly JPG images, some movies),
loading thumbnails for the whole timeline on Ryzen 5950X (Windows):
- 4.2.1: 35 seconds, CPU usage ~35%, UI smooth
- Main: 13 seconds, CPU usage ~90%, UI choppy
- This PR: 19 seconds, CPU usage ~35%, UI smooth
Manually made timeline with 10 video files:
- 4.2.1: 12 seconds, CPU usage ~50%, UI smooth
- Main: 6 seconds, CPU usage ~100%, UI choppy
- This PR: 9 seconds (no proxies) / 4 seconds (with proxies), CPU usage
~50%, UI smooth
Candidate for 4.5.x backport
Pull Request: https://projects.blender.org/blender/blender/pulls/144120
2f68e7e4b4