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From John Schulz <sch...@pythian.com>
Subject Re: Understanding C* -XX:MaxTenuringThreshold=1
Date Mon, 26 Oct 2015 10:56:26 GMT
You are correct. That is the intent of the MaxTenuringThreshold parameter.
Setting the value > 1 keeps objects in survivor space longer, if there is
space to keep them. The intent of keeping objects in survivor space for
longer than one ParNew cycle is to prevent relatively short lived objects
from being promoted to old gen space if they are just going to be
eliminated in the next CMS collection its better to keep them in survivor
space.

On Mon, Oct 26, 2015 at 12:18 AM, qihuang.zheng <
qihuang.zheng@fraudmetrix.cn> wrote:

> As Cassandra default *-XX:MaxTenuringThreshold=1*, which means:
> first time YGC, Eden's live object copy to Survivor(S0), those survivor
> object's age counter=1.
> Then next time YGC, Eden live object and S0 will copy to S1. and those
> still live object from S0 age counter=2 which large than
> MaxTenuringThreshold=1, then they will promot to Old Gen.
>
> from this, I get this conclusion:
> 1. After YGC, Eden live object copy to to survivor(age=1), from
> survivor(age=2) first copy to to survivor then transfer to old gen.
> 2. Old Gen's increment size after this YGC will not large than latest from
> survivor's size.
> 3. Survivor's object age counter aways be 1. as those counter=2 promot to
> Old, then disappear from survivor.
>
> Plz tell me it’s right.
> TKS.
>
> qihuang.zheng
>



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John H. Schulz

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