Number of Parallel GC Threads

[Jon Masamitsu]

kirk wrote On 01/23/09 11:19,:

>Jon Masamitsu wrote:
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>>kirk wrote On 01/23/09 09:39,:
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>>>I've come into a couple of situations where I need to throttle back on 
>>>GC threads so I think the request to throttle based on the -Xmx setting 
>>>seem reasonable.
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>>How do you decide the number of GC threads given a maximum heap size?
>>Do you scale the number of GC threads linearly with the maximum
>>heap size?
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>Good question. As Tony pointed out, there seems to be a useful number of 
>threads to allocate and so his formulation deviates from linear in cases 
>where there are a large number of CPUs. In this case I guess I would cap 
>at the min offered by that value and one determined by memory. I don't 
>have a good feeling for what that other formula would look like but a 
>good starting point could be something like 1 for something like every 
>64mb. The actual value could be adjusted using some observations about 
>how GC was behaving.
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So linear with the max size of the heap (e.g., 8 GC threads for a 512m
max heap)
up to some cap (e.g., using the 5/8's rule Tony described).

What do you mean by GC behavior?  And adjusting for it?