Java Reference
In-Depth Information
Flag
What it does
When to use it
See also
Affects how often incremental
CMS background threads run.
When using incremental CMS
and experiencing concurrent
mode failures, increase this
value, though setting CMSIncre-
mentalModeSafetyFactor is pre-
ferred.
Incremental
CMS
-XX:CMSIncrementalDutyCycleMax= N
Affects how often incremental
CMS background threads run.
When using CMSIncrement-
alDutyCycleMin , set this flag.
Incremental
CMS
-XX:+CMSIncrementalDutyCycle
Table A-6. Flags for the G1 collector
Flag
What it does
When to use it
See also
Hints to the G1 collector
how long pauses should
be; the G1 algorithm is
adjusted to attempt to
meet that goal.
As a first step in tuning
the G1 collector; increase
this value to attempt to
prevent full GCs.
Understanding
the G1 Col-
lector
-XX:MaxGCPauseMillis= N
Sets the number of threads
to use for G1 background
scanning.
When lots of CPU is
available and G1 is exper-
iencing concurrent mode
failures.
Understanding
the G1 Col-
lector
-XX:ConcGCThreads= N
Sets the point at which G1
background scanning be-
gins.
Lower this value if G1 is
experiencing concurrent
mode failures.
Understanding
the G1 Col-
lector
-
XX:InitiatingHeapOccupancyPercent= N
Sets the number of mixed
GCs over which G1 at-
tempts to free the garbage
old generation regions.
Lower this value if G1 is
experiencing concurrent
mode failures; increase it
if mixed GC cycles take
too long.
Understanding
the G1 Col-
lector
-XX:G1MixedGCCountTarget= N
Sets the size of a G1 re-
gion.
Increase this value for
very large heaps, or when
the application allocates
very, very large objects.
G1 region
sizes
-XX:G1HeapRegionSize= N
 
 
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