Re: [jbosscache-dev] VAM in JDBCCacheLoader : performance numbers and analysis
On 28 Dec 2006, at 00:05, Galder Zamarreno wrote:
Hi,
I've been doing some performance tests for JDBCCacheLoader with
both normal Java Serialization and VersionAwareMarshaller, using
the existing JDBCCacheLoaderPerfTest.
The results I got back were quite suprising. Executing a test
consisting of 10 threads (each thread interacts with a single node)
and each thread adds 100 key/value pairs to their node. Tests
showed that normal serialization was something like 15 times faster
than VAM when it came to writes. For reads, normal serialization
was still 4 times faster. We're talking about String/String key
value pairs here.
Looking a bit deeper with the profiler, I have seen that
TreeCacheMarshaller200 takes ages marshalling a map containing
string key/value pairs. Is this expected? We're adding quite a few
things to a simple String/String map, such as versioning and
reference information. Compared to standard writeObject in HashMap,
TreeCacheMarshaller200 spends quite a bit of time mantaining/
updating a reference map.
It is possible that such a reference map is meaningless in the case
of writing to a cache loader. It makes sense streaming on the wire
for an RPC call though. So maybe there needs to be an overloaded
form of objectTo|FromByteBuffer that could disable the ref map?
In this case, for a single put, each key and value values are
different (key0/value0 key1/value1 key2/value2...), maintaining
references becomes an extra overhead as the reference maps are
created for each request to marshall the original map. However, I
can see the point why it was done (avoid extra serialization and
reduce the amount of data in the wire).
I had a quick thought about caching reference data so that it
survived several requests to marshal data, but it's probably a bad
idea as this cache would become a contention for concurrent
marshalling and increase the memory requirements. Has anyone been
this route before? I think it might only produce positive results
in such specific test as this.
I tried JBoss serialization and the results were even worse. What
type of Objects is JB serialization recommended for? Is it user
defined ones?
User defined ones, yes.
I have attached JProfiler files from all three tests and also a CVS
diff in case anyone wants to have a quick glance. Note that even
though there's 1000 calls to marshallMap, as threads add new key/
value pairs, the data read-to-be-updated increases and hence the
number of items to iterate through in the map.
In any case, as Bela mentioned, a unit test that benchmarks the VAM
on it's own (against Java serialization) makes sense.
FYI, useRegionBasedMarshalling is set to false.
Galder Zamarreño
Sr. Software Maintenance Engineer
JBoss, a division of Red Hat
IT executives: Red Hat still #1 for value http://www.redhat.com/
promo/vendor/
<JBCACHE-897-serialization.java-10-100.jps>
<JBCACHE-897-serialization.jboss-10-100.jps>
<Head-serialization.java-10-100.jps>
<diff.27.12.2006.txt>
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