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https://issues.apache.org/jira/browse/AVRO-746?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12993753#comment-12993753
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Scott Carey commented on AVRO-746:
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That sounds about right. Atomic increments are a lot more expensive than a
simple increment, since it has to push the value to the processor cache and
notify any other processors that may have copies of the cache line. And
because an ordinary increment is basically the cheapest thing you can ask a CPU
to do. However, such increments are rarely a big chunk of the total work.
Very heavy multi-threaded access will likely show a bigger performance hit.
> Atomic reference counts
> -----------------------
>
> Key: AVRO-746
> URL: https://issues.apache.org/jira/browse/AVRO-746
> Project: Avro
> Issue Type: Bug
> Components: c
> Reporter: Douglas Creager
> Assignee: Douglas Creager
> Attachments: 0001-Atomic-reference-counts.patch,
> 0001-Performance-test-program.patch,
> 0002-Serialization-performance-test.patch, fixed-make-dist.patch
>
>
> In one of my projects that uses Avro, I pass avro_datum_t instances between
> threads, using the reference count mechanism to make sure that they're not
> freed while any thread still has a reference to them. I was getting some
> spurious segfaults, which were caused by the fact that the reference counts
> aren't updated atomically. I've created a patch that implements atomic
> reference counts, using the [OpenPA
> library|http://trac.mcs.anl.gov/projects/openpa/] to provide the atomic
> operations themselves. (That library is MIT licensed, so it can be included
> in the source tree.)
> Note that only avro_XXX_incref and avro_XXX_decref are thread-safe as a
> result of this patch. For all of the other library functions, the caller is
> still responsible for ensuring thread safety.
> The patch makes sure that the OpenPA code works in both the old autotools
> build and the newer CMake build.
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