Question about Object Copy times

[Yu Zhang]

Hi,

can you reduce MaxGCPauseMillis to ~300 or 200, 1000 maybe too high, and 
the eden size is ~80g, survivor size 2.5g. This might make the old gen 
getting full quicker so more mixed gc, but worth a try. Also, if you can 
add -XX:+PrintAdaptiveSizePolicy, it might tell us more.

It seems you are on an older version of jvm. can you move to later 
jdk8u40 or jdk8u60?

Thanks,
Jenny

On 8/20/2015 5:27 PM, D vd Reddy wrote:
> Hi,
>
> We are running G1 GC with heap size of around 140 - 150 GB, we are 
> observing high object copy times during young gc (> 80 % of the total 
> GC time).
> Is this expected or is there anything we are doing wrong. I am not 
> able to find any documentation of optimizing high object copy times,
> any help would be appreciated
>
>
> CommandLine flags: -XX:+AggressiveOpts 
> -XX:InitialHeapSize=154618822656 -XX:+ManagementServer
> -XX:MaxGCPauseMillis=1000 -XX:MaxHeapSize=154618822656 
> -XX:MaxMetaspaceSize=268435456
> -XX:MetaspaceSize=268435456 -XX:ObjectAlignmentInBytes=16
> -XX:+PrintGC -XX:+PrintGCDetails -XX:+PrintGCTimeStamps 
> -XX:+UnlockExperimentalVMOptions
> -XX:-UseCompressedOops -XX:+UseG1GC
>
>
> Sample young GC snippet
>
>
>
> 4416.985: [GC pause (G1 Evacuation Pause) (young), 0.3180932 secs]
>    [Parallel Time: 291.1 ms, GC Workers: 23]
>       [GC Worker Start (ms): Min: 4416985.5, Avg: 4416985.9, Max: 
> 4416986.2, Diff: 0.7]
>       [Ext Root Scanning (ms): Min: 1.2, Avg: 1.7, Max: 4.4, Diff: 
> 3.2, Sum: 38.5]
>       [Update RS (ms): Min: 36.3, Avg: 39.4, Max: 40.0, Diff: 3.8, 
> Sum: 906.0]
>          [Processed Buffers: Min: 47, Avg: 80.9, Max: 124, Diff: 77, 
> Sum: 1861]
>       [Scan RS (ms): Min: 0.5, Avg: 1.0, Max: 1.1, Diff: 0.6, Sum: 22.5]
>       [Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 
> 0.0, Sum: 0.6]
>       [Object Copy (ms): Min: 247.1, Avg: 247.2, Max: 247.5, Diff: 
> 0.4, Sum: 5686.4]
>       [Termination (ms): Min: 0.0, Avg: 0.3, Max: 0.4, Diff: 0.4, Sum: 
> 7.5]
>       [GC Worker Other (ms): Min: 0.0, Avg: 0.3, Max: 0.7, Diff: 0.7, 
> Sum: 7.6]
>       [GC Worker Total (ms): Min: 289.4, Avg: 290.0, Max: 290.4, Diff: 
> 1.0, Sum: 6669.3]
>       [GC Worker End (ms): Min: 4417275.5, Avg: 4417275.8, Max: 
> 4417276.2, Diff: 0.7]
>    [Code Root Fixup: 0.4 ms]
>    [Code Root Migration: 0.5 ms]
>    [Clear CT: 9.3 ms]
>    [Other: 16.8 ms]
>       [Choose CSet: 0.0 ms]
>       [Ref Proc: 3.7 ms]
>       [Ref Enq: 0.1 ms]
>       [Free CSet: 6.0 ms]
>    [Eden: 80.3G(80.3G)->0.0B(81.7G) Survivors: 2944.0M->2176.0M Heap: 
> 126.4G(144.0G)->45.4G(144.0G)]
>  [Times: user=6.84 sys=0.01, real=0.32 secs]
>
> Full GC Log for a period of run : 
> https://gist.github.com/dvdreddy/5ecf9a58a3f309e8bb60
>
>
> Thanks in advance
>
>
>
>
>
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