Andrea Del Bene created WICKET-7003:
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Summary: The http RequestLogger is very expensive. #524
Key: WICKET-7003
URL: https://issues.apache.org/jira/browse/WICKET-7003
Project: Wicket
Issue Type: Improvement
Reporter: Andrea Del Bene
The http RequestLogger is very expensive. In our system, we see almost 4kb of
memory allocation in this code to create a logging String that is ~700 bytes
long, per logging message being created.
* the use of AppendingStringBuffer immediately doubles the memory requirement
compared to StringBuilder as the former treats
all characters as UTF16. The log messages here appear to be mostly Latin1.
* Calls to getRequestHandlerString allocate an AppendingStringBuffer, resize
it once, and then call toString().
This results in nearly 1KB of garbage object creation (along with 5 objects)
and repeated data copies per call.
* Portions of the final String will have been copied up to 5 times in the
accumulation of the logging String.
Much better would be to have a single StringBuilder that is used repeatedly,
with the createRequestData() call synchronized.
This would save ~800 bytes of memory per logging request. I did not implement
that here as I expect some push back on serializing that call. Logging has to
be serialized anyway to avoid interleaving the output, and if logging is a
contention hotspot
then the rest of the application isn't doing much work.
The impact here is to act as an L1 D$ flush in the processor. While this code
might be fast (it will clearly evidence high hit rates in the cache), it evicts
other data from the L1 D$ resulting in subsequent code being slower.
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