Status: New
Owner: liuj...@google.com
Labels: Type-Defect Priority-Medium
New issue 464 by ryan.fog...@gmail.com: Inefficient Java handling of
repeated list of primitive types
http://code.google.com/p/protobuf/issues/detail?id=464
What steps will reproduce the problem?
1. Any handling of Protobuf message with a large set of repeated primitive
fields ([packed=true] or not).
For instance:
messages Foo {
...
repeated float data = 10; // optionally [packed=true]
}
2. Create handler that deals with large numbers of Foos with large data.
3. Use a profiler to monitor the large number of autoboxed types that slam
the GC.
What is the expected output? What do you see instead?
The output is as expected, except the Java garbage collector is slammed
because of having to manage a large number autoboxed primitive wrappers
because of the use of a java.util.List Collection as the code-generated
field type.
What version of the product are you using? On what operating system?
2.4.0a, 2.4.1, but confirmed that inefficiencty still exists in 2.5.0.
Linux/RedHat, Java 1.6.X.
Please provide any additional information below.
I have attached a (bzipped) patch file that has a solution that uses a
backend primitive_type[] that grows linearly as needed (much like a deque).
It avoids having to generate autoboxed wrappers for repeated primitive
types thus alleviating tons of work by the GC. Also, exposed a new
interface that breaks immutability at the expense of performance by
allowing the array[] type to be returned so that a client can make use of
functions such as System.copy. If preserving immutability is absolutely
mandatory then it may be necessary to provide a copy function (which takes
an array_type[] reference as its argument) or incur an additional array
clone/copy before returning the data (probably not the preferred approach).
Enquired about this on the Google Groups protobuf forum months ago but only
got a single response that someone would be interested in the fix. Link to
that conversation is here:
https://groups.google.com/d/msg/protobuf/w8lYLRW1wLY/cFbCMkknIHgJ
Attachments:
java_primitive_field.cc.patch.bz2 2.8 KB
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