Tenuring distribution

[Y.S.Ramakrishna at Sun.COM]

On 08/ 3/09 12:01 PM, Sujit.Das at cognizant.com wrote:
> Hi All,
>  
> I am trying to look whether there is any scope in improving tenuring 
> distribution by changing survivor space or Max Tenuring Threshold. I 
> have read some Tenuring distribution examples. But following tenuring 
> distribution output of my application confuses me and not sure whether 
> the young generation is well-tuned or not. The following tenuring 
> distribution O/P is result of consecutive minor collections. It 
> increases from age 1 to 3 (sometimes upto age 4) and then drops to age 
> 1. It then again increases with each minor collection.

Yes, as you can see, the TT drops to 3 and then to 1, and this
happens because there is periodically a large number of young survivors
(i.e. age 1) in the survivor space, so we pro-actively promote at the
next scavenge to avoid the possibility of premature overflow. You could increase your
survivor space size. (There is clearly some kind of periodic generation
of a large volume of data in your application. You can see whether that
correlates to any kind of load-pulsing, or convoying effects. Are you
using a production load (which can be bursty) or a bursty test load
or a uniform test load for these figures?)

Once again, I think Tony & Charlie's talk slides will help in this kind of
tuning.

-- ramki

>  
> Please do let me know your thoughts.
>  
> Desired survivor size 14188544 bytes, new threshold 4 (max 4)
> - age   1:    7040008 bytes,    7040008 total
> : 305088K->13787K(305088K), 0.0395292 secs] 
> 906769K->626948K(3044288K)After GC:
> ...
> Desired survivor size 14188544 bytes, new threshold 4 (max 4)
> - age   1:    6448424 bytes,    6448424 total
> - age   2:    4461088 bytes,   10909512 total
> : 291163K->12426K(305088K), 0.0191044 secs] 
> 904324K->625588K(3044288K)After GC:
> ...
> Desired survivor size 14188544 bytes, new threshold 3 (max 4)
> - age   1:    7150744 bytes,    7150744 total
> - age   2:    4394936 bytes,   11545680 total
> - age   3:    3582184 bytes,   15127864 total
> : 289802K->19070K(305088K), 0.0191912 secs] 
> 902964K->632232K(3044288K)After GC:
> ...
> Desired survivor size 14188544 bytes, new threshold 1 (max 4)
> - age   1:   18196472 bytes,   18196472 total
> - age   2:    3800224 bytes,   21996696 total
> - age   3:    3340344 bytes,   25337040 total
> : 296446K->27712K(305088K), 0.0282980 secs] 
> 909608K->648613K(3044288K)After GC:
> ...
> Desired survivor size 14188544 bytes, new threshold 4 (max 4)
> - age   1:    5757968 bytes,    5757968 total
> : 305088K->13117K(305088K), 0.0403760 secs] 
> 925989K->645051K(3044288K)After GC:
> ...
> Desired survivor size 14188544 bytes, new threshold 4 (max 4)
> - age   1:    5984000 bytes,    5984000 total
> - age   2:    4197480 bytes,   10181480 total
> : 290493K->13133K(305088K), 0.0251218 secs] 
> 922427K->645067K(3044288K)After GC:
> ...
> Desired survivor size 14188544 bytes, new threshold 3 (max 4)
> - age   1:    6765056 bytes,    6765056 total
> - age   2:    4159752 bytes,   10924808 total
> - age   3:    3534520 bytes,   14459328 total
> : 290509K->17608K(305088K), 0.0258073 secs] 
> 922443K->649542K(3044288K)After GC:
> ...
> Desired survivor size 14188544 bytes, new threshold 1 (max 4)
> - age   1:   17919056 bytes,   17919056 total
> - age   2:    4852200 bytes,   22771256 total
> - age   3:    3152768 bytes,   25924024 total
> : 294984K->27712K(305088K), 0.0303612 secs] 
> 926918K->667692K(3044288K)After GC:
> ...
> Desired survivor size 14188544 bytes, new threshold 4 (max 4)
> - age   1:    6579448 bytes,    6579448 total
> : 305088K->13396K(305088K), 0.0386087 secs] 
> 945068K->664582K(3044288K)After GC:
>  
> Thanks,
> Sujit
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