(unnecessary?) sync locking when checking if Native is loaded causes unneeded slowdown

[noamBarkai]

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When using this library in a highly concurrent setting - vis. Apache Spark - I'm seeing a lot of contention around this synchronisation block, specifically when called from here It seems the synchronisation is somewhat redundant and that it can safely be removed, assuming the boolean member loaded is modified to volatile, no? I can offer a PR if you feel like wise.

[odaira]

Yes, I think changing loaded to volatile will work. If you still see the contention problem and if you submit a PR, I'll take a look at it.

[noamBarkai]

@odaira - it's been a while since this issue was opened... :) I'm not sure if this problem still persists, but regardless I can open a PR, no problem, I don't think it's harmful.

[noamBarkai]

https://github.com/lz4/lz4-java/pull/126

[odaira]

Thanks much for your contribution. Because I am about to release a new version, I'll review this after that.

[JoshRosen]

In Spark, https://github.com/apache/spark/pull/24905 may partially mitigate this by significantly reducing the number of calls to fastestInstance().