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8246037: Shenandoah: update man pages to mention -XX:+UseShenandoahGC

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Reviewed-by: ysr, wkemper, cslucas
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Rui Li 2025-09-02 23:49:23 +00:00 committed by Kelvin Nilsen
parent b50c11f907
commit 5052a7eee5
2 changed files with 44 additions and 2 deletions
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6
src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp
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@ -141,10 +141,12 @@
"GC heuristics to use. This fine-tunes the GC mode selected, " \
"by choosing when to start the GC, how much to process on each " \
"cycle, and what other features to automatically enable. " \
"Possible values are:" \
"When -XX:ShenandoahGCMode is generational, the only supported " \
"option is the default, adaptive. Possible values are:" \
" adaptive - adapt to maintain the given amount of free heap " \
"at all times, even during the GC cycle;" \
" static - trigger GC when free heap falls below the threshold;" \
" static - trigger GC when free heap falls below a specified " \
"threshold;" \
" aggressive - run GC continuously, try to evacuate everything;" \
" compact - run GC more frequently and with deeper targets to " \
"free up more memory.") \

40
src/java.base/share/man/java.md
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@ -2882,6 +2882,46 @@ Java HotSpot VM.
expensive operations. Using a lower value will cause heap memory to be
uncommitted earlier, at the risk of soon having to commit it again.
`-XX:+UseShenandoahGC`
: Enables the use of the Shenandoah garbage collector. This is a low pause
time, concurrent garbage collector. Its pause times are not proportional to
the size of the heap. Shenandoah garbage collector can work with compressed
pointers. See `-XX:UseCompressedOops` for further information about
compressed pointers.
`-XX:ShenandoahGCMode=`*mode*
: Sets the GC mode for Shenandoah GC to use. By default, this option is set
to `satb`. Among other things, this defines which barriers are in use.
Possible mode values include the following:
`satb`
: Snapshot-at-the-beginning concurrent GC (three pass mark-evac-update).
It is a single generation GC.
`generational`
: It is also a snapshot-at-the-beginning and concurrent GC, but it is
generational. Please see [JEP 404](https://openjdk.org/jeps/404) and
[JEP 521](https://openjdk.org/jeps/521) for its advantages and risks.
`-XX:ShenandoahGCHeuristics=`*heuristics*
: Sets the heuristics for Shenandoah GC to use. By default, this option is
set to `adaptive`. This fine-tunes the GC mode selected, by choosing when
to start the GC, how much to process on each cycle, and what other features
to automatically enable. When `-XX:ShenandoahGCMode` is `generational`, the
only supported option is the default, `adaptive`.
Possible heuristics are the following:
`adaptive`
: To maintain the given amount of free heap at all times, even during
the GC cycle.
`static`
: Trigger GC when free heap falls below a specified threshold.
`compact`
: Run GC more frequently and with deeper targets to free up more memory.
## Deprecated Java Options
These `java` options are deprecated and might be removed in a future JDK