UseAdaptiveGCBoundary?

Srinivas Ramakrishna ysr1729 at gmail.com
Thu Feb 9 08:47:32 PST 2012


Thanks Jon for the informative response!

-- ramki

On Thu, Feb 9, 2012 at 6:39 AM, Jon Masamitsu <jon.masamitsu at oracle.com>wrote:

> 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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