RFR [8011215] optimization of CopyOnWriteArrayList.addIfAbsent() (original) (raw)

Martin Buchholz martinrb at google.com
Tue Apr 2 22:47:54 UTC 2013

On Tue, Apr 2, 2013 at 3:45 PM, Ivan Gerasimov <ivan.gerasimov at oracle.com>wrote:

Thank you, Ulf!

maybe the old code wins for looong arrays, so there could be a threshold to decide between old and new code:

I've modified the benchmark code to test arrays with 90'000 to 100'000 elements. (Previously was testing 1 to 100 elements.) The performance gain turns out to be even more significant. On my machine tests show that with that many elements the new code runs 40% faster. Honestly, I didn't expect that. I thought my code might be a bit slower and hoped that not much slower.

Yeah, that's a bit surprising. Perhaps because you're avoiding the branch of testing object for null on each iteration?

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