what about Azul's Zing JVM?

[Gary Berger]

Yes, Zing is a concurrent mark-and-compact GC, compaction being the somewhat
harder. Originally the C4 collector ran on custom Vega processors and than
leveraged hypervisor based memory mapping features (EPT) to flip pages, now
they have figured out how to do it on bare Linux with a kernel module..
Would be great to get these changes in the upstream kernel.

Gil gave a great talk about Zing 5 at QCON

http://bit.ly/vN5xQ0

.:|:.:|:.  Gary Berger | Architect, Office of the CTO, DSSG | Cisco Systems|
One Penn Plaza | New York, NY 10119 | Phone: 917.288.8691

From:  Vitaly Davidovich <vitalyd at gmail.com>
Date:  Mon, 28 Nov 2011 09:10:47 -0500
To:  Li Li <fancyerii at gmail.com>
Cc:  hotspot-gc-use <hotspot-gc-use at openjdk.java.net>
Subject:  Re: what about Azul's Zing JVM?


As a gross oversimplification their GC is concurrent to mutator (java)
threads but is mostly pauseless (they still pause at times but only very
briefly) because they use read barriers.   This means that if a mutator
thread reads memory that's been relocated, they trap this condition at read
time, fix up the pointer (mutator does this itself), and continue on.  Last
I heard this approach required azul's os support for bulk in/mapping of
pagetable entries, and required a Linux patch for x86 to do the same (but it
wasn't accepted into mainline kernel).

What's interesting is whether hotspot has any plans to do something similar?

On Nov 28, 2011 4:27 AM, "Li Li" <fancyerii at gmail.com> wrote:
> hi everybody,
>     I read an article today about Azul's Zing JVM. It is said that this jvm is
> pauseless.
>     In my application, our machine is about 48GB and about 25GB memory is
> given to jvm(by -Xmx). But it will occasionally pause 1-2 seconds.
>     So when I saw this, I want to know whether it's so good as they say. And I
> googled and found a related question in stackoverflow:
> http://stackoverflow.com/questions/4491260/explanation-of-azuls-pauseless-garb
> age-collector
>     after reading, I am still confusing. Anyone would give more detail
> explanations about it? thanks
> 
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> hotspot-gc-use mailing list
> hotspot-gc-use at openjdk.java.net
> http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use
> 
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