RFR (S) CR 8006627: Improving performance and reducing object allocations of java.util.UUID to/from string (original) (raw)

Steven Schlansker stevenschlansker at gmail.com
Fri Feb 1 18:13:01 UTC 2013

On Jan 30, 2013, at 11:42 AM, Mike Duigou <mike.duigou at oracle.com> wrote:

Good work Steven!

Thanks for the review :)

Some initial comments; - The changes to Long should be in a separate issue. It's generally encouraged for changesets to focus on only one change. Sorry, yes, it's additional overhead.

That's unfortunate. I don't have the ability / know how to file a second, separate issue, and I've already spent a lot more time trying to get this small change through than I'd expected on overhead. Will it be preferable to have someone open a second issue, make two web revs, and code review both, or should I just abandon the attempt at code-sharing between UUID and Long? In the original patch that Aleksey reviewed I had not attempted this; I did it on his suggestion.

- I would like to see if performed of toString() can be improved further by using String(char[] value, boolean share) constructor via a sun.miscSharedSecret.JavaLangAccesss method to construct the string directly from the character array. You could test to see if this has positive benefit by temporarily using a static char array.

I will incorporate this into my next revision

- public static String toString(long msb, long lsb) should be private. There's no compelling reason to add this to the API.

I can remove this. I added it on the theory that if you wish to ship UUIDs around as two longs, it may be useful to omit UUID object instantiation just to format as a string. Maybe this is too far out there to make another public method acceptable.

- Have you run this code against any of the existing regression tests?

Yes, I ran the jtreg UUID and Long tests, all pass. I ran the Apache Harmony UUID test cases against the pre-integrated version of the code. (There should only have been minor modifications since then, variable renamings, whatnot…)

Mike On Jan 28 2013, at 19:23 , Steven Schlansker wrote:

http://bugs.sun.com/bugdatabase/viewbug.do?bugid=8006627

I have created a patch that dramatically improves UUID to/from string performance. Please find below a webrev with my proposed changes. Thanks in advance for any feedback on the contents. I do not believe I have a committer lined up yet. My company has a signed OCA on file, "Ness Computing". http://dl.dropbox.com/u/1422321/uuidwebrev/index.html http://dl.dropbox.com/u/1422321/uuidwebrev.zip

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