Question about Object Copy times

Fri Aug 21 03:21:19 UTC 2015

Hi,

I have enable -XX:+PrintTenuringDistribution -XX:+PrintAdaptiveSizePolicy
and moved to a newer build (1.8.0_45). No major improvements but I am
seeing new information.

Also Is the Desired Survivor Size printed by Tenuring Distribution only a
approximate value ? I am seeing it is significantly lower than the final
Survivor Size.

The new logs are here :
https://gist.github.com/dvdreddy/1cb9829e526d419d8452

Thanks

PS: I am starting new experiment with lower max pause, will post results
later.

On Thu, Aug 20, 2015 at 6:24 PM, D vd Reddy <dvdeepankar.reddy at gmail.com>
wrote:

> Thanks, I will add the -XX:+PrintAdaptiveSizePolicy, and will try to move
> the jvm
>
> But about the old gen getting full, there is a contradicting point that
> the overall heap size is going down at the same size as the size of eden
> minus size of survivor, So I feel that the old size is not going up by
> that much. Also in the logs I saw that Mixed GC is not happening that
> frequently only 8 mixed compared to 380 young.
>
> Am I missing something here ?
>
>
> Thanks,
>
>
> On Thu, Aug 20, 2015 at 6:14 PM, Yu Zhang <yu.zhang at oracle.com> wrote:
>
>> 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
>>
>>
>>
>>
>>
>> _______________________________________________
>> hotspot-gc-use mailing listhotspot-gc-use at openjdk.java.nethttp://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use
>>
>>
>>
>
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