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refine the Guide section in incremental GC

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Matthew Flatt 2015-12-01 17:47:29 -07:00
parent d56e7309ad
commit 345b1a8187
1 changed files with 5 additions and 8 deletions
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pkgs/racket-doc/scribblings/guide/performance.scrbl
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@ -583,13 +583,10 @@ garbage collected, and thus the red fish is not either.
By default, Racket's @tech{generational garbage collector} creates By default, Racket's @tech{generational garbage collector} creates
brief pauses for frequent @deftech{minor collections}, which inspect brief pauses for frequent @deftech{minor collections}, which inspect
only the most recently allocated objects, and long pauses for infrequent only the most recently allocated objects, and long pauses for infrequent
@deftech{major collections}, which re-inspect all memory. Weak @deftech{major collections}, which re-inspect all memory.
references (as described in
@secref["Reachability\x20and\x20Garbage\x20Collection"]) are cleared
only by a major collection.
For soft real-time applications, such as animations, games, and some For some applications, such as animations and games,
network services, long pauses due to a major collection can interfere long pauses due to a major collection can interfere
unacceptably with a program's operation. To reduce major-collection unacceptably with a program's operation. To reduce major-collection
pauses, the Racket garbage collector supports @deftech{incremental pauses, the Racket garbage collector supports @deftech{incremental
garbage-collection} mode. In incremental mode, minor collections garbage-collection} mode. In incremental mode, minor collections
@ -598,7 +595,7 @@ work toward the next major collection. If all goes well, most of a
major collection's work has been performed by minor collections the major collection's work has been performed by minor collections the
time that a major collection is needed, so the major collection's time that a major collection is needed, so the major collection's
pause is as short as a minor collection's pause. Incremental mode pause is as short as a minor collection's pause. Incremental mode
tends to use more memory and run more slowly overall, but it can tends to run more slowly overall, but it can
provide much more consistent real-time behavior. provide much more consistent real-time behavior.
If the @envvar{PLT_INCREMENTAL_GC} environment variable is set when If the @envvar{PLT_INCREMENTAL_GC} environment variable is set when
@ -612,7 +609,7 @@ Calling @racket[(collect-garbage 'incremental)] does not perform an
immediate garbage collection, but instead requests that each minor immediate garbage collection, but instead requests that each minor
collection perform incremental work up to the next major collection. collection perform incremental work up to the next major collection.
The request expires with the next major collection. Make a call to The request expires with the next major collection. Make a call to
@racket[(collect-garbage 'incremental)] in any periodic task within @racket[(collect-garbage 'incremental)] in any repeating task within
an application that needs to be responsive in real time. Force a an application that needs to be responsive in real time. Force a
full collection with @racket[(collect-garbage)] just before an initial full collection with @racket[(collect-garbage)] just before an initial
@racket[(collect-garbage 'incremental)] to initiate incremental mode @racket[(collect-garbage 'incremental)] to initiate incremental mode