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From: Robert Klemme <shortcutter@googlemail.com>
Newsgroups: comp.lang.java.programmer
Subject: Re: java8 up to 6x slower than java7
Date: Sat, 15 Feb 2014 12:55:23 +0100
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On 15.02.2014 12:00, Dennis Haupt wrote:
> i wrote a little pathfinder. i can run it under the jdk7 update 51
> and it is done in ~20 seconds. under java8, since a long series of
> builds, a certain part involving deeeeeeeeeep recursion takes ~60
> seconds instead of 10. i suspected the hashmap change of java8 to be
> the culprit since i perform a lot of put operations, but that's not
> it - i used the standard  hashmap from scala to be 100% sure the
> hashmap can't be the reason (or is), and indeed, i get the same
> performance difference between java7 and 8 with the same hashmap my
> profiler (yourkit) shows that java8 spends a much bigger amount of
> time on garbage collection and allocated more objects. if i take a
> memory snapshot, can see that the final results are equal, so i have
> more temporary objects. yourkit also shows that more objects are
> allocated using java8. what is up with that? all i do in the critical
> method is creating arraylists and performing puts, contains and gets
> on a hashmap, and the recursive call. the time is, according to
> yourkit, spend in the method itself, not inside the hashmap or
> arraylist constructor. any ideas?

Does your profiler not show allocation hotspots?  Other than that it's 
just wild speculation without seeing the code.

Cheers

	robert