UseAdaptiveGCBoundary?

Jon Masamitsu jon.masamitsu at oracle.com
Thu Feb 9 06:39:22 PST 2012


Ramki,

I cannot say that I would recommend it's use.  The problem with 
UseAdaptiveGCBoundary
is all in the policy that it uses to decide how to move the boundary.  
It used to sometimes
back itself into a corner (young gen size and old gen size which was sub 
optimal)
and not be able to get itself out.  I think that can still be a problem 
but perhaps the
bigger problem is that the policy thinks that it is optimal to divide 
the the GC times
  evenly between the young GC's and old GC's and that is not always the 
case.  In
general that policy produces reasonably good results but when that 
policy can
drive the moving of the boundary, I've seen cases where there are 
performance
regressions (i.e., GC ergonomics turned on but worse performance when the
boundary moving is additionally turned on).

Jon

On 2/7/2012 9:04 AM, Srinivas Ramakrishna wrote:
> Hi Jon, John, et al. --
>
> What's the current status of and experience with UseAdaptiveGCBoundary?
> As I recall a (long) while ago there was some performance issue with it,
> although
> I can't recall the specific details.
> Is this flag something you recommend trying out? Are there performance
> sharp-corners that one should watch out for if one were to enable this
> feature ?
>
> thanks for any tips!
> -- ramki
>


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