Maximum value allowed for derby.storage.fileCacheSize (100) is too low for
large system. Increase the maximum value and redocument the property.
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Key: DERBY-3734
URL: https://issues.apache.org/jira/browse/DERBY-3734
Project: Derby
Issue Type: Bug
Components: Performance
Affects Versions: 10.3.3.0
Environment: Derby 10.3.3
Reporter: Stan Bradbury
Increasing the value of the undocumented property: derby.storage.fileCacheSize
improves Derby performance in our system but the maximum allowed value (100) is
not large enough to accommodate our system. Our performance engineer reports:
The following stack shows items being evicted from Derby's container cache.
Extra debug code showed that the cache was at its maximum size (100), and that
about 1 in 25 accesses to the cache was resulting in a miss (forcing another
item to be evicted). Since this results in synchronous disk write, performance
is bottlenecked on IO. Patching Derby to allow the cache to grow to 200
entries solved the performance problem.
Performance is severely degraded. CPU utilization is low -- performance is IO
bound. A sampling of stack dumps for the key thread consistently have the
following methods at the top of the stack:
at sun/nio/ch/FileChannelImpl.force0(Native Method)
at sun/nio/ch/FileChannelImpl.force(FileChannelImpl.java:392(Compiled Code))
at org/apache/derby/impl/io/DirRandomAccessFile4.sync(Bytecode PC:5(Compiled
Code))
at org/apache/derby/impl/store/raw/data/RAFContainer.writeRAFHeader(Bytecode
PC:86(Compiled Code))
at org/apache/derby/impl/store/raw/data/RAFContainer.clean(Bytecode
PC:84(Compiled Code))
at org/apache/derby/impl/services/cache/CachedItem.clean(Bytecode PC:7(Compiled
Code))
at org/apache/derby/impl/services/cache/Clock.rotateClock(Bytecode
PC:7(Compiled Code))
at org/apache/derby/impl/services/cache/Clock.findFreeItem(Bytecode
PC:17(Compiled Code))
at org/apache/derby/impl/services/cache/Clock.find(Bytecode PC:71(Compiled
Code))
at
org/apache/derby/impl/store/raw/data/BaseDataFileFactory.openContainer(Bytecode
PC:65(Compiled Code))
at
org/apache/derby/impl/store/raw/data/BaseDataFileFactory.openContainer(Bytecode
PC:7(Compiled Code))
at org/apache/derby/impl/store/raw/xact/Xact.openContainer(Bytecode
PC:29(Compiled Code))
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