Details
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Type:
Improvement
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Status: Closed
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Priority:
Major
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Resolution: Fixed
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Affects Version/s: None
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Fix Version/s: 4.0
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Component/s: None
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Labels:None
Description
Right now log record serialization is synchronized. We can improve concurrency by serializing to a ram buffer outside synchronization. The cost will be RAM usage for buffering, and more complex concurrency in the tlog itself (i.e. we must ensure that a close does not happen without flushing all in-RAM buffers)
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It looks like there's a bug lurking here.... I'm looking into it.
http://find.searchhub.org/document/7510cdb2423bcf7d
I just committed the fix for the bug introduced by this issue.
http://svn.apache.org/viewvc?view=revision&revision=1374480
Closed after release.
Here's a patch that moves log record serialization outside of the synchronized block.
All tests pass, but I could detect no meaningful speedup on my system.
After further investigation, I believe this is due to the fact that our binary (javabin) serialization is really fast. I did some profiling and it was between .25% (sampling) and 2% (instrumentation) of the total runtime. Removing synchronization around such a small percent of time is not going to show up much on my 4 CPU box.
I still plan to commit this as it still represents an architectural improvement, may be more mesurable in high-core systems, and is a stepping stone toward future improvements.