<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; color: rgb(0, 0, 0); "><div><div><div style="font-family: Calibri, sans-serif; font-size: 14px; ">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.</div><div style="font-family: Calibri, sans-serif; font-size: 14px; "><br></div><div style="font-family: Calibri, sans-serif; font-size: 14px; ">Gil gave a great talk about Zing 5 at QCON</div><div style="font-family: Calibri, sans-serif; font-size: 14px; "><br></div><div style="font-family: Calibri, sans-serif; font-size: 14px; ">http://bit.ly/vN5xQ0</div><div style="font-family: Calibri, sans-serif; font-size: 14px; "><br></div><div><div><div style="font-family: Calibri, sans-serif; font-size: 14px; "><font class="Apple-style-span" face="Consolas" size="3"><span class="Apple-style-span" style="font-size: 11px; ">.:|:.:|:. Gary Berger | Architect, Office of the CTO, DSSG | Cisco Systems</span></font><span class="Apple-style-span" style="font-family: Consolas; font-size: 11px; ">| One Penn Plaza | New York, NY 10119 | Phone: 917.288.8691</span></div></div></div></div></div><div style="font-family: Calibri, sans-serif; font-size: 14px; "><br></div><span id="OLK_SRC_BODY_SECTION" style="font-size: 14px; font-family: Calibri, sans-serif; "><div style="font-family:Calibri; font-size:11pt; text-align:left; color:black; BORDER-BOTTOM: medium none; BORDER-LEFT: medium none; PADDING-BOTTOM: 0in; PADDING-LEFT: 0in; PADDING-RIGHT: 0in; BORDER-TOP: #b5c4df 1pt solid; BORDER-RIGHT: medium none; PADDING-TOP: 3pt"><span style="font-weight:bold">From: </span> Vitaly Davidovich <<a href="mailto:vitalyd@gmail.com">vitalyd@gmail.com</a>><br><span style="font-weight:bold">Date: </span> Mon, 28 Nov 2011 09:10:47 -0500<br><span style="font-weight:bold">To: </span> Li Li <<a href="mailto:fancyerii@gmail.com">fancyerii@gmail.com</a>><br><span style="font-weight:bold">Cc: </span> hotspot-gc-use <<a href="mailto:hotspot-gc-use@openjdk.java.net">hotspot-gc-use@openjdk.java.net</a>><br><span style="font-weight:bold">Subject: </span> Re: what about Azul's Zing JVM?<br></div><div><br></div><p>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).</p><p>What's interesting is whether hotspot has any plans to do something similar?</p><div class="gmail_quote">On Nov 28, 2011 4:27 AM, "Li Li" <<a href="mailto:fancyerii@gmail.com">fancyerii@gmail.com</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">hi everybody,<div> I read an article today about Azul's Zing JVM. It is said that this jvm is pauseless.</div><div> 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.</div><div> 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: <a href="http://stackoverflow.com/questions/4491260/explanation-of-azuls-pauseless-garbage-collector" target="_blank">http://stackoverflow.com/questions/4491260/explanation-of-azuls-pauseless-garbage-collector</a></div><div> after reading, I am still confusing. Anyone would give more detail explanations about it? thanks</div><br>_______________________________________________<br>
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