Emulator Issues #8598: OGL: zfreeze reads from WRITE_ONLY mapped buffer - Emulator - Dolphin bug tracker

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Emulator Issues #8598

closed

OGL: zfreeze reads from WRITE_ONLY mapped buffer

Added by degasus almost 9 years ago.

Status:

Fixed

Priority:

High

Assignee:

% Done:

Operating system:

N/A

Issue type:

Bug

Milestone:

Current

Regression:

Relates to usability:

Relates to performance:

Easy:

Relates to maintainability:

Regression start:

Fixed in:

Description

The current zfreeze code reads the last position from the vertex buffer. This buffer is given by the backend as WRITE_ONLY. On OpenGL, this is often a write_combined memory, so every read operation will fall back to uncached memory. This ends in a 5% real time usage because of waiting for memory.

Officially, this is a OpenGL violation. So newer driver may also read-protect this page and dolphin may crash.

There is a fix as WIP:
https://github.com/dolphin-emu/dolphin/pull/2141

The broken access is in:
https://github.com/dolphin-emu/dolphin/blob/master/Source/Core/VideoCommon/VertexManagerBase.cpp#L302