JEP 144: Reduce GC Latency for Large Heaps

Tony Printezis tony.printezis at oracle.com
Wed Feb 29 09:23:44 PST 2012


Todd,

I recently pushed a change that causes G1 to be more aggressive when 
choosing which old regions to collect during mixed GCs. I think it still 
needs a bit more fine-tuning but it's much better compared to what we 
had before which I admit it was sub-optimal and fiddly. It should 
address both issues you mentioned below.

Tony

On 02/28/2012 07:18 PM, Todd Lipcon wrote:
> Hi Mark, G1 team,
>
> Do you have any plans to address either of the problems discussed in
> the thread "G1GC Full GCs" from January '11?
>
> To refresh/summarize, the problems were:
> 1) If the process is context-switched out during the "Other time"
> accounting, and this causes the "other time" to eclipse the pause time
> goal, then it will never again select any non-young regions for
> collection until the next full GC.
> http://mail.openjdk.java.net/pipermail/hotspot-gc-use/2011-January/000781.html
> There's a simple patch linked above which solved this problem for my usecase.
>
> 2) If a region, at any time during its lifetime, overflows its fine
> rset accounting, it's easy for it to become uncollectable despite a
> very high garbage ratio:
> http://mail.openjdk.java.net/pipermail/hotspot-gc-use/2011-January/000785.html
> I worked on some patch for this but wasn't able to get good results in
> the day or two that I allotted.
>
> -Todd
>
> On Tue, Feb 28, 2012 at 4:01 PM,<mark.reinhold at oracle.com>  wrote:
>> Posted: http://openjdk.java.net/jeps/144
>>
>> - Mark
>
>


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