8344727: [JVMCI] Export the CompileBroker compilation activity mode for Truffle compiler control

[simonis]

Truffle compilations run in "hosted" mode, i.e. the Truffle runtimes triggers compilations independently of HotSpot's CompileBroker. But the results of Truffle compilations are still stored as ordinary nmethods in HotSpot's code cache (with the help of the JVMCI method jdk.vm.ci.hotspot.HotSpotCodeCacheProvider::installCode()). The regular JIT compilers are controlled by the CompileBroker which is aware of the code cache occupancy. If the code cache runs full, the CompileBroker temporary pauses any subsequent JIT compilations until the code cache gets swept (if running with -XX:+UseCodeCacheFlushing -XX:+MethodFlushing which is the default) or completely shuts down the JIT compilers if running with -XX:+UseCodeCacheFlushing.

Truffle compiled methods can contribute significantly to the overall code cache occupancy and they can trigger JIT compilation stalls if they fill the code cache up. But the Truffle framework itself is neither aware of the current code cache occupancy, nor of the compilation activity of the CompileBroker. If Truffle tries to install a compiled method through JVMCI and the code cache is full, it will silently fail. Currently Truffle interprets such failures as transient errors and basically ignores it. Whenever the corresponding method gets hot again (usually immediately at the next invocation), Truffle will recompile it again just to fail again in the nmethod installation step, if the code cache is still full.

When the code cache is tight, this can lead to situations, where Truffle is unnecessarily and repeatedly compiling methods which can't be installed in the code cache but produce a significant CPU load. Instead, Truffle should poll HotSpot's CompileBroker compilation activity and pause compilations for the time the CompileBroker is pausing JIT compilations (or completely shutdown Truffle compilations if the CompileBroker shut down the JIT compilers). In order to make this possible, JVMCI should export the CompileBroker compilation activity mode (i.e. stop_compilation, run_compilation or shutdown_compilation).

The corresponding Truffle change is tracked under #10133: Implement Truffle compiler control based on HotSpot's CompileBroker compilation activity.

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Issue

• JDK-8344727: [JVMCI] Export the CompileBroker compilation activity mode for Truffle compiler control (Enhancement - P4)

Reviewers

• Doug Simon (@dougxc - Reviewer)

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[openjdk]

@simonis This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8344727: [JVMCI] Export the CompileBroker compilation activity mode for Truffle compiler control

Reviewed-by: dnsimon

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At the time when this comment was updated there had been 53 new commits pushed to the master branch:

• 6f622da: 8344923: Problem list on java/awt/Robot/ScreenCaptureRobotTest.java on macOS
• 8f08020: 8344903: Improve error handling TestJhsdbJstackPrintVMLocks.java
• a83cfe2: 8344917: Fix recent NULL usage backsliding
• 6711e13: 8344914: OOME in several tests since JDK-6672644 - JComboBox still scrolling
• a6220fa: 8344303: Remove usage of URLUtil.getConnectPermission from sun.awt.SunToolkit and sun.awt.image.URLImageSource
• 7be94d0: 8344891: Remove uses of sun.misc.ReflectUtil in java.desktop
• 822a155: 8341427: JFR: Adjust object sampler span handling
• d00f311: 8343150: Change URLClassLoader.getPermissions to return empty PermissionCollection
• effee12: 8344533: CTW: Add option to remove clinits before loading
• 70c4e2c: 8344587: Reduce number of "jdk.jpackage.internal" classes used from other packages
• ... and 43 more: https://git.openjdk.org/jdk/compare/882d6358074135b2c4fe21b32bd73f40022980bc...master

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[dougxc]

Looks good.