AAShapePipe concurrency & memory waste (original) (raw)
Laurent Bourgès bourges.laurent at gmail.com
Fri Apr 5 12:20:20 UTC 2013
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Dear java2d members,
I figured out some troubles in java2d.pipe.AAShapePipe related to both concurrency & memory usage:
- concurrency issue related to static theTile field: only 1 tile is cached so a new byte[] is created for other threads at each call to renderTile()
- excessive memory usage (byte[] for tile, int[] and rectangle): at each call to renderPath / renderTiles, several small objects are created (never cached) that leads to hundreds megabytes that GC must deal with
Here are profiling screenshots:
4 threads drawing on their own buffered image (MapBench test): http://jmmc.fr/~bourgesl/share/AAShapePipe/AAShapePipe_byte_tile.png
excessive int[] / Rectangle creation: http://jmmc.fr/~bourgesl/share/AAShapePipe/AAShapePipe_int_bbox.png http://jmmc.fr/~bourgesl/share/AAShapePipe/AAShapePipe_rectangle_bbox.png
Here is the proposed patch: http://jmmc.fr/~bourgesl/share/AAShapePipe/webrev-1/
I applied a simple solution = use a ThreadLocal or ConcurrentLinkedQueue (see useThreadLocal flag) to cache one AAShapePipeContext per thread (2K max). As its memory footprint is very small, I recommend using ThreadLocal.
Is it necessary to use Soft/Weak reference to avoid excessive memory usage for such cache ?
Is there any class dedicated to such cache (ThreadLocal with cache eviction or ConcurrentLinkedQueue using WeakReference ?) ? I think it could be very useful at the JDK level to have such feature (ie a generic "GC friendly"cache )
Regards, Laurent
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