Need help on G1 GC young gen Update RS and Scan RS pause reduction

[charlie hunt]

No, if this is Solaris, continue to use large pages. There are no known issues with using large pages on Solaris (SPARC or x86/x64).

Charlie 

> On Feb 6, 2017, at 3:17 AM, Amit Mishra <amit.mishra at redknee.com> wrote:
> 
> Hi Charlie,
>  
> This is solaris OS and there is flag argv[46]: -XX:+UseLargePages  which is enabled, do you recommend to disable it.
>  
> Also per Thomas suggestion I am trying to figure out Java 1.8 compatible with our Apps and will use that in further testing.
>  
> Thanks,
> Amit Mishra
>  
> From: charlie hunt [mailto:charlie.hunt at oracle.com] 
> Sent: Saturday, February 4, 2017 00:12
> To: Thomas Schatzl <thomas.schatzl at oracle.com>
> Cc: Amit Mishra <amit.mishra at redknee.com>; hotspot-gc-use at openjdk.java.net
> Subject: Re: Need help on G1 GC young gen Update RS and Scan RS pause reduction
>  
> > “- from one gc to another, just for these four gcs, sys time is relatively high.”
>  
> Assuming this is on Linux … perhaps double check that THP (transparent huge pages) is disabled.
>  
> charlie
>  
> On Feb 3, 2017, at 7:01 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
>  
> Hi Amit,
> 
> On Fri, 2017-02-03 at 11:09 +0000, Amit Mishra wrote:
> 
> Hi Thomas/team,
> 
> 
> I have put all parameters as per your suggestion but somehow the
> minor gc pauses are still haunting.
> 
> Attaching GC logs.
> 
> 
> bash-3.2$ grep -i young gcstats.log.10636|cut -d, -f2|awk -F" "
> '{print $1}'|awk '$1 > 1'
> 1.1273134
> 1.1683221
> 3.5504848
> 5.2693987
> 
>   looking at these log entries, there seems to be something going on
> that seems outside of VM control:
> 
> - from one gc to another, just for these four gcs, sys time is
> relatively high.
> 
> - for the last two occurrences, at least one thread is hanging in "Ext
> Root Scanning" for almost all of the gc time for no obvious reason.
> 
> - there do not seem to be an unusually large amount of changes in the
> amount of work done in the particular phases that would raise immediate
> concerns to me.
> 
> Please try to find out the source of the high sys time and maybe even
> what causes it. I can't help a lot in that area, but dtrace seems a
> good starting point as suggested earlier.
> 
> I think we went through most obvious tunings now, but maybe somebody else has more ideas. I don't at this time.
> 
> The jdk (7u45) you are using is also very old, so even if we find that
> there is something wrong with g1 in particular, I kind of doubt there
> are many more useful knobs to turn with that version (or even
> appropriate logging to find out about the actual issue). Since 7u45
> release, there have been hundreds of changes that in particular improve
> G1 performance, so please consider upgrading to something more recent
> (at least latest 8u, preferably to me some test runs with 9ea).
> Upgrading alone might already help.
> 
> Thanks,
>   Thomas
> 
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>  
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