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List:       openjdk-hotspot-gc-dev
Subject:    DGC and UseParallelOldGC
From:       Jon.Masamitsu () Sun ! COM (Jon Masamitsu)
Date:       2009-10-14 13:40:29
Message-ID: 4AD5D4CD.6040501 () Sun ! COM
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On 10/13/09 18:10, Rainer Jung wrote:
> On 14.10.2009 01:35, Jon Masamitsu wrote:
>> Rainer Jung wrote On 10/13/09 15:46,:
>>
>>> Hi all,
>>>
>>> if I activate the parallel stop the world collector using
>>> -XX:+UseParallelOldGC and DGC kicks in: will it run with multiple
>>> threads in parallel, or will it only run single-threaded?
>> I'm assuming you mean that you are using the throughput collector
>> (UseParallelGC/UseParallelOldGC) in which case turning on
>> UseParallelOldGC will use multiple threads for an explicit GC.
>> (System.gc()).
> 
> Yes that was the question, but also especially for the distributed GC
> triggered by RMI. When using CMS you have to explicitely set flags to
> let DGC also use the CMS. So since UseParallelOldGC is not the default I
> wasn't sure, whether you need to set something in analogy to let the
> distributed GC also use it.
> 

Yes for the distributed GC case multiple GC threads will be used.

A GC triggered by RMI (for distributed GC purposes) is the same as
a explicit GC (no special treatment).  Similarly, when you use
CMS and ExplicitGCInvokesConcurrent and/or 
ExplicitGCInvokesConcurrentAndUnloadsClasses all the
explicit GC's are affected.
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