Number of Parallel GC Threads

[kirk]

Jon Masamitsu wrote:
> Tony Printezis wrote On 01/23/09 07:33,:
>
>   
>> Nick,
>>
>> First, a correction. For very large machines, we don't set the number of 
>> GC threads to be the same as the CPUs (there are diminishing returns if 
>> we do that). Currently, you get 1 parallel GC thread per CPU for up to 8 
>> CPUs, and 5/8 after that (so for 16 CPUs you get: 8 + 5/8 x 8 = 13 GC 
>> threads).
>>
>>  
>>
>>     
> Tony,
>
> This is a bit of embarassment on my part.  What you say is true
> for all the collectors except UseParallelGC.  In the early jdk6's
> and before,  we used all the cpu's for GC for UseParallelGC
> (the default for server-class machines).  That was fixed in
> jdk6 update 10 (I believe).
>
> Jon
>
>   
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.

Regards,
Kirk