Hi reveman@, make sure we are talking about the same thing:

On eve, when logging out, the screen becomes black and lasts about 3 seconds to show the pod.
When logging in, it takes 3 seconds after pressing enter, and followed about 2 seconds black screen to show the desktop.

Choose different wallpaper and remove the blur does not help.

I remember there was discussion that to reduce the time of black screen when logging out. But I cannot find the bug. It may be different issue.

+bccheng@, who might have other tools to analyze what happened.

According to the bug description, the issue should be the same with  crbug.com/779311 . (Both '2 seconds of UI raster when entering/leaving lock screen' and wallpaper delay are observed in this issue.)

I think #1 may be referring to a different issue.

#3, I think I am seeing the same thing in  crbug.com/779311 , after you pressing enter, it stays on login page for about 3 seconds for EVE. But in addition, there are 2 seconds black screen followed.

Is the 3 seconds the normal time for the preparation of active user session? The 2 seconds of the blank screen is caused by the CL mentioned in  crbug.com/779311 .

#5, Interesting, it is the same cl I bisected at here:  crbug.com/780000 

is that change in M63?

The CL mentioned in #5 [1] is 852d42a7... and landed initially in 64.0.3250.0.


[1] https://chromium-review.googlesource.com/c/chromium/src/+/728325

The bug in this issue may not be caused by the cl mentioned in #5. I am on a build without the cl in #5, still seeing the long time delay.

The entire wallpaper is re-rastered when going into/out of lock-screen/login pages, right? Is that the problem? What if you change the code to not show the wallpaper at all? Does that reduce the raster time by much? (of course, that's not what we would want to do, but that could help isolate the issue)

The CL mentioned above is what caused the problem. It introduced a a color space conversion for each pixel which is not something we can do in the UI compositor that uses software raster. I verified that this issue is gone in ToT now that the effect of that CL has been moved behind a flag that is disabled by default.