G1GC: many consecutive full gcs (was Re: hotspot-gc-use Digest, Vol 40, Issue 4)

[Y. S. Ramakrishna]

Stefan and Alex --

(1) what's the version of the JVM used?

(2) could you try PermSize == MaxPermSize and see if it made any
     difference?

(3) do you have lots of WeakReference or Finalizer objects in your system?

(4) is what you have below your complete GC log (i.e. no gaps between first and last line?)

(5) what do you see when using CMS (in case you tried it)?

(6) do you have a simple test case that you can share with
     us that exhibits this behaviour?

thanks!
-- ramki

On 06/16/11 14:02, Alex Aisinzon wrote:
> Stefan
> 
> I have had similar experience with G1 and reported it here.
> I tried the option to try to limit GC pauses (-XX:MaxGCPauseMillis with
> 1s and then 2s). It did not improve things.
> I am happy to try anything else to help improve G1.
> 
> Alex A
> 
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>    1. G1GC: many consecutive full gcs (Stefan Wachter)
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> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Thu, 16 Jun 2011 09:23:05 +0200
> From: Stefan Wachter <Stefan.Wachter at gmx.de>
> Subject: G1GC: many consecutive full gcs
> To: hotspot-gc-use at openjdk.java.net
> Message-ID: <4DF9AF59.90708 at gmx.de>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> Hi all,
> 
> the G1GC runs nicely for some time but then it starts to have bursts of 
> consecutive full gcs (see log below). Can anyone explain that behaviour?
> 
> The JVM is stared with these options:
> 
> -Xmx10000M
> -Xms1024M
> -XX:MaxPermSize=1024m
> -XX:+UseG1GC
> -XX:MaxGCPauseMillis=2000
> -XX:GCPauseIntervalMillis=10000
> 
> --Stefan
> 
> 
> 31314.569: [GC pause (young) 3286M->3234M(8937M), 0.0485530 secs]
> 31374.932: [GC pause (young) 3279M->3236M(8937M), 0.0486560 secs]
> 31837.688: [GC pause (young) 4614M->3252M(8937M), 0.0739370 secs]
> 33528.784: [GC pause (young) 5997M->3330M(8937M), 0.1543940 secs]
> 35372.029: [GC pause (young) 6038M->3405M(8937M), 0.2364930 secs]
> 36508.343: [Full GC 8525M->2903M(9678M), 8.9121160 secs]
> 38204.291: [Full GC 8647M->2295M(10000M), 7.4105940 secs]
> 39038.017: [Full GC 8790M->2092M(6975M), 6.7242110 secs]
> 39047.736: [Full GC 8996M->2089M(9998M), 6.0741630 secs]
> 39095.551: [Full GC 8936M->2090M(6969M), 5.5573390 secs]
> 39104.326: [Full GC 9175M->2092M(9997M), 5.3413860 secs]
> 39112.760: [Full GC 9392M->2094M(9978M), 5.4884150 secs]
> 41965.304: [Full GC 9549M->2112M(7043M), 6.4774550 secs]
> 43830.656: [GC pause (young) 4615M->2309M(7043M), 0.1727720 secs]
> 46024.398: [GC pause (young) 4638M->2497M(7043M), 0.3039900 secs]
> 46068.009: [Full GC 8832M->2237M(10000M), 6.6717340 secs]
> 46077.691: [Full GC 9322M->2187M(9987M), 5.8603570 secs]
> 46086.731: [Full GC 9487M->2189M(9996M), 5.8521360 secs]
> 46124.713: [Full GC 8792M->2185M(9895M), 5.7782260 secs]
> 46133.366: [Full GC 9297M->2188M(9999M), 5.7263360 secs]
> 46142.238: [Full GC 9509M->2189M(9985M), 5.5704850 secs]
> 47454.530: [Full GC 9676M->2295M(7653M), 7.3169840 secs]
> 48163.422: [GC pause (young) 4937M->2431M(7653M), 0.2379570 secs]
> 48887.388: [GC pause (young) 5007M->2497M(7653M), 0.1999790 secs]
> 
> 
> 
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