RFR: JDK-8086056: ParNew: auto-tune ParGCCardsPerStrideChunk

Jon Masamitsu jon.masamitsu at oracle.com
Thu Jun 18 17:13:48 UTC 2015

On 06/18/2015 06:27 AM, Tony Printezis wrote:
> Hi Jon,
> Thanks for looking at it. I can definitely add an additional bool flag 
> to turn it on or off. I think it will also make sense to make it 
> manageable so that we can switch the auto-tuning on / off dynamically, 
> if necessary.


When you were doing the performance testing, did you have some type of 
so that you could see the cards-per-stride-chunk that was being used?   
someone is going to ask for it so if you had something succinct I'd be 
glad to see it
included in this push.

> Tony
> On June 17, 2015 at 9:46:16 PM, Jon Masamitsu 
> (jon.masamitsu at oracle.com <mailto:jon.masamitsu at oracle.com>) wrote:
>> Tony,
>> I'm still studying the patch but would you consider a more explicit
>> flag to turn this on and off?  What you have is very reasonable but
>> if the performance team sees some regression, it would be easier
>> for them to turn the feature on or off rather than go look for the value
>> of ParGCCardsPerStrideChunk that is the default and then put that
>> on the command line.  Same would be true for a customer who has
>> an application operating in one of the corners where the performance
>> is worse.
>> Jon
>> On 6/17/2015 3:30 PM, Tony Printezis wrote:
>>> Hi all,
>>> A small patch for your consideration:
>>> http://cr.openjdk.java.net/~tonyp/8086056/webrev.0/ 
>>> <http://cr.openjdk.java.net/%7Etonyp/8086056/webrev.0/>
>>> (BTW, for some reason some of the webrev output is a bit messed up. 
>>> Not sure why, maybe some hg incompatibility I guess. The diffs look 
>>> OK though. I also attached the patch to this e-mail.)
>>> There’s a bit of info on the JIRA on the rationale for the patch:
>>> https://bugs.openjdk.java.net/browse/JDK-8086056
>>> The min / max values for the old gen capacity 
>>> and ParGCCardsPerStrideChunk were chosen empircally after running a 
>>> few (mostly synthetic tests) on Linux x64. If someone has the cycles 
>>> to do a more extensive performance study, I’d be happy to revise 
>>> them accordingly.
>>> Regards,
>>> Tony
>>> -----
>>> Tony Printezis | JVM/GC Engineer / VM Team | Twitter
>>> @TonyPrintezis
>>> tprintezis at twitter.com <mailto:tprintezis at twitter.com>
> -----
> Tony Printezis | JVM/GC Engineer / VM Team | Twitter
> @TonyPrintezis
> tprintezis at twitter.com <mailto:tprintezis at twitter.com>

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