Memory leak when viewing mpv fullscreen

[pedrocr]

• Sway Version: sway version 1.2-fa0abaf7 (Oct 21 2019, branch 'master')
• Debug Log: https://gist.github.com/pedrocr/539daf0639eb4f8ee112eb1639d5a4e7
• MPV Debug Log: https://gist.github.com/pedrocr/5e1f6e1f406f63bebfa31ee734abb5be
• Configuration File: default config

Either sway or mpv are doing something wrong when fullscreen that results in memory being unreclaimed in the kernel. Only killing sway returns the memory to use. Here's how to reproduce:

• Open a terminal running top and a video file with mpv next to it
• Notice the "avail Mem" section of top that shows the available memory discounting the buffers that can be easily reclaimed
• As the video plays that value will remain relatively constant if there's nothing else consuming memory in the system
• Now make mpv fullscreen for a few seconds and come back. Now the available memory will go down significantly. In my system that was 2GB/hour of video but I'm sure that will vary depending on the video or screen resolution.

Killing mpv does not reclaim the memory but killing sway does. Running mpv with gpu-context=waylandvk seems to fix it or at least reduce it very significantly. I get video tearing with that option though.

At least on my system I can reproduce this at will right now so I can gather more info if wanted.

[pedrocr]

Instead of top looking up /proc/meminfo seems to work too. When fullscreen MemAvailable goes down because Unevictable grows.

[pedrocr]

Another evidence of a leak is that when the video is fullscreen something like this:

sudo cat /sys/kernel/debug/dri/0/framebuffer | grep sway | wc -l

shows the number of allocated framebuffers climbing rapidly (100 more in a few seconds).

[heghe]

I think this bug is related to this line

bo = import_gbm_bo(&drm->renderer, &conn->pending_dmabuf);

After importing the buffer we never destroy it. The import_gbm_bo documentation say that should be freed with destroy_gbm_bo, but we never do this.

[pedrocr]

There seems to be something specific to how mpv is handling fullscreen that triggers the bug. Fullscreen youtube videos in Firefox don't seem to cause the same issue. I'm using the latest mpv release (0.29.1) as packaged by Ubuntu 19.04.

[ascent12]

@pedrocr It's definitely a bug on our side; not particularly related to mpv. mpv just happens to be a client that is capable of hitting the direct-scanout optimisation for you.

@heghe Yeah, that'd be it.

[emersion]

Can you try swaywm/wlroots#1872?

[pedrocr]

@emersion from 5 minutes of testing that seems to fix it, thanks. I'm now running that patched version and will keep monitoring to see if there's anything else.