JDK-8258918 : [macosx] Java forces the use of discrete GPU
  • Type: CSR
  • Component: client-libs
  • Sub-Component: 2d
  • Priority: P3
  • Status: Draft
  • Resolution: Unresolved
  • Fix Versions: tbd
  • Submitted: 2020-12-24
  • Updated: 2021-07-13
Related Reports
CSR :  
JDK-8251854 - [macosx] Java forces the use of discrete GPU
Description
Summary
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Switch Java 2D on macOS from using the high performance, high power consumption graphics card to the lower performance, lower power consumption graphics card.

Problem
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All 15" or 16" Macbook Pros to date have two video cards.
An AMD discrete graphics card and the integrated Intel one on the CPU.
Since Java has never requested the integrated one, then it causes the discrete
one to be initialised. Most other apps, including the bundled ones request the integrated one.
This means that when a Java UI app is started the system will draw more power, even if
running on battery, since Apple does not provide sufficient control over this situation.
This behaviour of defaulting to the discrete card is a consequence of a compatibility decision by Apple.
See https://developer.apple.com/library/archive/qa/qa1734/_index.html#//apple_ref/doc/uid/DTS40010791

Solution
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Add  the "NSSupportsAutomaticGraphicsSwitching" key to the Info.plist for the java executable,
so applications started that way will use the integrated video card, and will not force the discrete video card.

It is known that Java2D's OpenGL pipelline works fine on the integrated video card, because that is all that is available on various systems (Intel mac mini, 13" MacBook Pro, Air, etc). So we can use the integrated video by default.

This change also improves startup performance, on a 2019 16" MacBook Pro running macOS  11.1 the switching between discrete/integrated causes unexpected delays up to 10 seconds. Although this is not a problem on older releases, so is likely a macOS bug that should be fixed.

The drawback is that Java 2D performance will be lower on the integrated video card and this means lower than it has been in all Oracle JDK's for macOS since the first 7u2 release by Oracle.
We intend to release note this and describe workarounds.

As mentioned above Apple does not provide much application control over when the discrete card is used so even with this change it can still be used in some cases. Empirically these include :

     - If the app sets/uses a full-screen window
     - If the user disables "automatic graphics switching" in System Preferences
     - If an external monitor is connected to the laptop

Specification
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No change in the specification.