Yes, sync messages are required, the GPU is needed to show the UI at all.

What's surprising is that it takes 3s+ in CommandExecutor:PutChanged
Can you attach the contents of about:gpu?

It is still the same with today's build:
https://crrev.com/0026aed1b09b9d4d06da3ddc402e995bf57bfad8

Is there a work around for this issue?

Well it magically works faster now.

I am attaching contents of about:gpu when it is fast.
I can't get it back to slower state now.

I will attache the gpu again if it gets slow.

Deleted: gpu.html 53.3 KB

gpu.html 53.3 KB View Download

Nothing obvious from about:gpu, reasonably standard NVIDIA gpu/driver.

Ok, it got slow again, and this is what the gpu page shows now.

Deleted: gpu_slow.html 53.3 KB

gpu_slow.html 53.3 KB View Download

No difference, I don't know.

Can you dump the output of `nvidia-smi -q -d memory`?
It could be interesting to see the difference when slow vs when fast.

Are older builds actually better? If so, any chance you might be able to bisect?

Faster version:

 nvidia-smi -q -d memory

==============NVSMI LOG==============

Timestamp                           : Tue May 17 16:34:59 2016
Driver Version                      : 340.96

Attached GPUs                       : 1
GPU 0000:05:00.0
    FB Memory Usage
        Total                       : 1023 MiB
        Used                        : 986 MiB
        Free                        : 37 MiB
    BAR1 Memory Usage
        Total                       : 256 MiB
        Used                        : 8 MiB
        Free                        : 248 MiB

Slower version:

 nvidia-smi -q -d memory

==============NVSMI LOG==============

Timestamp                           : Tue May 17 17:08:28 2016
Driver Version                      : 340.96

Attached GPUs                       : 1
GPU 0000:05:00.0
    FB Memory Usage
        Total                       : 1023 MiB
        Used                        : 1005 MiB
        Free                        : 18 MiB
    BAR1 Memory Usage
        Total                       : 256 MiB
        Used                        : 8 MiB
        Free                        : 248 MiB

Not sure if older versions are better. I cannot practically bisect to find the CL because it is slow sometimes and faster sometimes.
Is there no way to find the cause of this by looking at the traces?

This time I also got a few log messages:
texture filtering.
[4526:4526:0517/171144:ERROR:gles2_cmd_decoder.cc(15078)] [.DisplayCompositor-0x150e48c08700]GL ERROR :GL_INVALID_OPERATION : glCreateAndConsumeTextureCHROMIUM: invalid mailbox name
[4526:4526:0517/171144:ERROR:gles2_cmd_decoder.cc(8222)] [.DisplayCompositor-0x150e48c08700]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.
[4526:4526:0517/171144:ERROR:gles2_cmd_decoder.cc(15078)] [.DisplayCompositor-0x150e48c08700]GL ERROR :GL_INVALID_OPERATION : glCreateAndConsumeTextureCHROMIUM: invalid mailbox name
[4526:4526:0517/171144:ERROR:gles2_cmd_decoder.cc(8222)] [.DisplayCompositor-0x150e48c08700]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.

Not sure if they are related.

It looks like you are really close to the max GPU memory. When the GPU runs out of memory, it has to page in and out and that's slow. I think that's what's happening to you.

A couple of things:
- what does `nvidia-smi -q -d memory` say when chrome is not running?
- if you open the Chrome task manager (shift-escape) what does the "GPU memory" column say for the "GPU process" line? (you may need to enable that column by right-clicking on the task manager).
- I'm afraid to suggest it, but it's possible that restarting your desktop session, or even rebooting may help.

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