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Status: Untriaged
Owner: ----
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Pri: 3
Type: Bug



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Slow input latency reported by slow-reports

Project Member Reported by etienneb@chromium.org, Jan 16 (6 days ago)

Issue description

We are receiving chrome traces from slow-reports when scrolling is too slow.

From this slow-reports:
  9ebb8f9bde0fabfe

We are observing 3 spikes in the InputLatency::MouseMove track.
There are >1.5 seconds long (see attachments).

The three spikes are aligned with the long tasks running in renderer (pid: 3104).

  ThreadControllerImpl::RunTask

 
input1.png
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input2.png
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Comment 1 by gab@chromium.org, Jan 16 (6 days ago)

Thanks, FTR b693f63cc917cb48 also exhibits this problem.

We will need traces with stack sampling on renderers hitting this problem.

Comment 2 by etienneb@chromium.org, Jan 16 (6 days ago)

From this slow-report: b693f63cc917cb48

The IO thread has a gab for about ~15 seconds while the MouseMove seems to go crazy. Everthing else on the browser side seems to make progress.
There is a task on thread 60168 (ThreadBrackgroundBocking3) which is running a task:
  "./../mojo/public/cpp/system/simple_watcher.cc"   "ArmOrNotify"

The Renderer 63304 is also blocked and aligned with these events.

I'm unsure about the cause, but having a task block on a background thread seems to point to a priority inversion.
mouse1.png
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mouse2.png
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mouse3.png
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Comment 3 by etienneb@chromium.org, Jan 16 (6 days ago)

I looked to these cases:

  c2940b5f34ec014b
  302be0389bb4129f
  29b9b924337e59c2
  649ebcd2e893c4a0
  efb56820803a918c

All of them as a long mouse input, and a renderer is also block/unblock at the same time that the input is processed.
case1.png
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case2.png
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case3.png
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case4.png
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case5.png
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