https://bugs.kde.org/show_bug.cgi?id=523812

--- Comment #7 from AccessWebBE <[email protected]> ---
(In reply to Zamundaaa from comment #6)
> Well, it sounds to me more like the driver is leaking stuff, and those
> buffers happen to be attributed to KWin. Until that part is fixed, I
> wouldn't want to spend any time investigating any possible issues in KWin
> that don't happen with other drivers.

Closing the loop on this one, since your answer turned out to be exactly right.

It was the driver. Zack Rusin (vmwgfx maintainer) explained on dri-devel that
vmwgfx never got the explicit prime export deref/destroy ioctls in the kernel
DRM uapi, so gem_close on resources created from fd handles did nothing there
and every one of them leaked. Thread and his reply:
https://lore.kernel.org/dri-devel/ (subject "drm/vmwgfx: graphics memory not
returned after all GEM objects are released", 5 August 2026). Mesa fix:
https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/43386

What actually made it go away on my side was enabling 3D acceleration in the
VMware host settings. Same machine, same kernel 7.1.6, same distribution mesa
26.1.6, no patch involved:

    3D disabled, 4 sessions of 8 to 35 hours    667 to 1367 MB/hour
    3D enabled  (svga), 2 sessions of 16-18h      5 and 22 MB/hour

Two things changed measurably at the same time. The TTM MOB pool had been
constant at 0.023 GB across 409 samples over four days and only started moving
once svga was in use, and the dominant buffer went from 8355840 bytes
(1920x1088x4, height padded to a multiple of 64, i.e. a dumb buffer) to 8294400
(1920x1080x4, exactly the screen). So the configuration I originally reported
was not going through gallium svga at all.

For anyone finding this later: if you run KWin in a VMware guest with 3D
acceleration turned off, this is what you hit. Turning it on is worth trying
before anything else.

Sorry for the noise on the KWin side, and thanks for the quick and correct
call.

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