Linux futex_wait() bug – update to latest patches now

Re:Linux futex_wait() bug – update to latest patches now by btrask on Wednesday May 13, 2015 @09:47PM (#9543058)

I'm not part of the Java world at all, but I'm starting to think that Azul Systems is one of the few groups of people who know what they're doing with regard to Linux performance and the user/kernel boundary. I recently watched some talks by Cliff Click[1] that were extremely informative, and from what I understand about their proposed kernel patches, they seem like important improvements.

This report by Gil Tene (their CTO according to Wikipedia) lends more support to that theory.

[1] https://www.youtube.com/watch?v=uL2D3qzHtqY

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Re:Linux futex_wait() bug – update to latest patches now by hga on Wednesday May 13, 2015 @09:55PM (#9543071)

Unfortunately, per Gin Tene as of a couple of years ago they've given up on that approach (getting kernel patches in): https://groups.google.com/d/msg/mechanical-sympathy/UnsLM6wh...

A shame, since those would allow some really sweet things for garbage collectors, which evidently isn't a goal.

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Re:Linux futex_wait() bug – update to latest patches now by click170 on Wednesday May 13, 2015 @11:08PM (#9543242)

I'm skeptical of the way the author framed the discussion around his patches, I believe the majority of people out there are genuinely not evil, people don't often reject contributions that have clear benefits without reason, and I find it's often best to get said reason straight from the horses mouth.

Does anyone have a link to that discussion? I get the sense there is more to that discussion than the author let on in his brief response.

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Re:Linux futex_wait() bug – update to latest patches now by Jach on Thursday May 14, 2015 @02:04AM (#9543664)

I got the sense too. The message sharing the link to the source describes it as "incomplete and extremely buggy". Was it that way when it was first proposed to the kernel group for integration? If so that seems like a reasonable reason to reject it...

I googled for "kernel mailing list managed runtime initiative" and found this: https://lwn.net/Articles/392307/ Apparently it was never even proposed on the kernel mailing list! But then apparently the code as written wasn't ever meant to be integrated into the kernel upstream but as a sort of PoC that would maybe be a better starting point than going fresh for eventual integration... But there's lots of interesting details, and as I'm reading through the comments, things are coming back, now I remember reading about this in 2010/2011...

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Re:Linux futex_wait() bug – update to latest patches now by random3 on Wednesday May 13, 2015 @10:41PM (#9543180)

Also Cliff Click is doing H2O at 0xdata http://0xdata.com/team/cliff-click/

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Re:Linux futex_wait() bug – update to latest patches now by osi on Thursday May 14, 2015 @08:29AM (#9544696)

They absolutely do! If you purchase their Zing JVM, it is generally because of the very low GC pauses it brings. And after that occurs, you quickly start to notice what other things are going on on your system to cause unwanted pauses in your processes.

In order to effectively sell the JVM, they need to help you understand and reduce the non-GC pauses so you can realize the full value of your investment.

(full disclosure: happy Zing customer)

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