-XX:+UseNUMA in conjunction with -XX:+UseG1GC

[Per Liden]

Hi,

I don't think "Option is not recommended for use in productive 
environments" is a string printed by OpenJDK. If you're using SAP's JVM 
you'll have to ask SAP why they do that.

/Per

On 08/29/2018 09:59 AM, David Weeda wrote:
> Good Afternoon,
> 
> I have set the parameter in our development system however the following 
> message is now displayed in the start-up log.
> 
> J  Option is not recommended for use in productive environments: 
> -XX:+UseNUMA
> 
> Regards,
> 
> *David Weeda*
> 
> *SAP Technical Architect*
> 
> *From:*sangheon.kim at oracle.com <sangheon.kim at oracle.com>
> *Sent:* Wednesday, 29 August 2018 6:57 AM
> *To:* David Weeda <David.Weeda at det.nsw.edu.au>; 
> hotspot-gc-use at openjdk.java.net
> *Cc:* Jag Inturi <Jag.Inturi at det.nsw.edu.au>
> *Subject:* Re: -XX:+UseNUMA in conjunction with -XX:+UseG1GC
> 
> Hi David,
> 
> On 8/26/18 11:18 PM, David Weeda wrote:
> 
>     Hello,
> 
>     We are upgrading our SAP Java Application servers to use SAP JVM 8.1
>     Patch Collection 39. This release integrates updates from Oracle JDK
>     8u172
> 
>     The GC shall be switched from -XX:+UseConcMarkSweepGC to -XX:+UseG1GC.
> 
>     On the following website:-
> 
>     https://docs.oracle.com/javase/8/docs/technotes/guides/vm/performance-enhancements-7.html#numa
> 
>     There is a note on NUMA Collector Enhancements for the Parallel
>     Scavenger garbage collector. Are the subsequent collectors, namely
>     the G1 garbage collector also NUMA aware?
> 
> No, G1 is not NUMA aware. Only Parallel GC(-XX:+UseParallelGC) has NUMA 
> awareness.
> 
> 
>     Is it default?
> 
> If you are asking UseNUMA option is by default for G1GC, no UseNUMA is 
> always false by default.
> 
> 
>     May I use the -XX:+UseNUMA flag with -XX:+UseG1GC?
> 
> Yes, you can use +UseNUMA with +UseG1GC.
> G1 algorithm is not NUMA aware, but with UseNUMA enabled, we can get 
> NUMA interleaving. i.e. Interleave memory across NUMA nodes if possible 
> and this would give some benefits on NUMA system.
> FYI, UseNUMAInterleaving(false by default) command-line option will be 
> automatically enabled if UseNUMA is enabled.
> 
> HTH,
> Sangheon
> 
> 
> 
>     Regards,
> 
>     *David Weeda*
> 
>     *SAP Technical Architect | Enterprise Systems | Information
>     Technology Directorate *
> 
>     Level 11, 8 Central Ave | Eveleigh NSW 2015 | |(:+61 (0)4 8822 0280
>     | *: david.weeda at det.nsw.edu.au <mailto:david.weeda at det.nsw.edu.au>
>     | _www.dec.nsw.gov.au <http://www.dec.nsw.gov.au/>_
> 
>     cid:image003.png at 01D0B4D4.6A6EFF30
> 
> 
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