[Bug 97879] [amdgpu] Rocket League: long hangs (several seconds) when loading assets (models/textures/shaders?)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97879

--- Comment #55 from Timothee Besset <ttimo at ttimo.net> ---
Rocket League uses an async I/O thread to stream in content in the background.
That thread works off of a queue and only does disk reads and decompression (it
doesn't issue any OpenGL calls for instance, that happens on a dedicated render
thread).

The CPU usage you are seeing out of Rocket League is this thread being busy
with decompression. This is generally normal and not an indication of a
problem.

However, when running with radeonsi, the async I/O thread is performing very
poorly. Much, much worse than with amdgpupro. To the point that the main thread
has to wait for async and causes a significant hitch (up to 4 seconds in some
logs I captured).

I tend to agree that this problem is not related to shader compilation. The
bumps from shader compilation are barely showing up in profiles. But it's
definitely made a lot worse by running on radeonsi. On the same system with
amdgpupro those same hitches can happen but they are in the 100/200ms range.

At this point of the investigation, and due to scheduling constraints, I am
likely only going to come back to this once Timothy Arceri has a shader cache
implementation available. I suspect this will not help significantly but let's
hope I'm wrong there.

In the meantime there are some log files from the async thread compared between
radeonsi and amdgpu-pro if someone feels like extracting some possibly useful
data:

https://www.dropbox.com/s/d73jk66uhfrhv8l/amdgpupro-compressedread-timings.log?dl=0
https://www.dropbox.com/s/1xfl3l24f5buzs0/radeonsi-compressedread-timings.log?dl=0

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