PR #331 causes severe slowdown with SSBB + 4x SSAA

[Wisteso]

Edit: Bug post filed per recommendation at https://code.google.com/p/dolphin-emu/issues/detail?id=8441

I've been doing some experimenting after noticing some major FPS stuttering during "Brawl-mode character-select" in Super Smash Brothers Brawl with the latest development builds. However this issue did not happen with the latest stable build. I believe I've tracked down the exact issue by testing until I found the first build where the issue happens.

4.0-1603 did not have this performance issue
4.0-1609 had clear symptoms of the issue just like the latest version does

The only thing that appears to have changed during these builds is how the EFB functions ( https://github.com/dolphin-emu/dolphin/pull/331 )

Symptoms: Performance drops to about 80% (50ish fps, sound stuttering, etc) when in SSBB character select. Other common parts of the game seem to be fine (no stutter) though since FPS capped at 60 there might be unknown performance decreases in other areas.

Workaround/Solution: Setting Anti-Aliasing to "4x" instead of "4x SSAA" seems to solve the issue, though it may just be helping enough to get over 60 FPS? Perhaps there is no issue other than "4x SSAA" simply being incompatible with the EFB changes?

[degasus]

This PR should have increased the GPU load with MSAA and disabled "ingore efb format changes", but I don't see how SSAA is affected. Which GPU did you use for testing?
Just to be sure, you didn't compare SSAA vs CSAA, did you?

Also to validate my assumption, may you also check if this slowdown also happens at 1x IR? I guess it's a GPU internal performance issue.

[MayImilae]

Please create an issue on the issue tracker and move the conversation there: https://code.google.com/p/dolphin-emu/issues/list

[Wisteso]

MaJoR, I'm not able to create a bug report at the moment due to Google code giving server error (500 code) responses right now. I can later though hopefully.

(03-29-2015, 06:15 PM)degasus Wrote: This PR should have increased the GPU load with MSAA and disabled "ingore efb format changes", but I don't see how SSAA is affected. Which GPU did you use for testing?
Just to be sure, you didn't compare SSAA vs CSAA, did you?

I am using the GeForce GTX 750 Ti running driver 347.88

The only AA options presented to me are "4x SSAA", "FXAA" via post processing, and an generic "2x/4x/8x AA" (is that the MSAA?). Generic 4x AA and FXAA have no issues. It is only 4x SSAA that has the problems on build 4.0-1609 and newer.

(03-29-2015, 06:15 PM)degasus Wrote: Also to validate my assumption, may you also check if this slowdown also happens at 1x IR? I guess it's a GPU internal performance issue.

I can also confirm that the issue only happens when using > 1x internal resolution (so it does not happen at 1x). I am using "auto multiple" so I'm not sure the exact factor, but I imagine its using 2x since my screen is 1080p.

[Wisteso]

Bug has been posted to https://code.google.com/p/dolphin-emu/issues/detail?id=8441 - Just making a note of that here