Question about Object Copy times

[Tao Mao]

A bunch you could try:

1. Do you have a particular reason to set ObjectAlignmentInBytes=16? The
default is 8. A larger value may have more waste in object chunks. Just
remove it to have default.

2. One gc log shows you have 23 gc workers. Experiment with lower and
higher numbers depending on your machine constraints. May try 16 and 32 if
that's applicable.

3. If what you care is solely throughput, setting MaxGCPauseMillis to a
higher number (e.g., MaxGCPauseMillis=2000) may help, which is
counter-intuitive tho/

Try the above and good luck!

Thanks.
Tao Mao



On Mon, Aug 24, 2015 at 2:09 PM, D vd Reddy <dvdeepankar.reddy at gmail.com>
wrote:

> Oh sorry for the mistake in the throughput definition,
>
> The options we were using were just setting MaxGCPause to 1000ms, here is
> the exhaustive list
> "-XX:+AggressiveOpts -XX:InitialHeapSize=154618822656
> -XX:+ManagementServer -XX:MaxGCPauseMillis=1000
> -XX:MaxHeapSize=154618822656 -XX:MaxMetaspaceSize=268435456
> -XX:MetaspaceSize=268435456 -XX:ObjectAlignmentInBytes=16
> -XX:+PrintAdaptiveSizePolicy -XX:+PrintGC -XX:+PrintGCDetails
> -XX:+PrintGCTimeStamps -XX:+PrintTenuringDistribution
> -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions
> -XX:-UseCompressedOops -XX:+UseG1GC "
>
> The numbers we were seeing in other applications (one is HBase)  were
> close to 99 % , that's when we took a look in the GC logs to see if there
> is anything more we can extract, the only thing that caught our eye was the
> high object copy times which we did not see in the other applications.
>
> Thanks for the help and suggestions.
>
>
> On Mon, Aug 24, 2015 at 12:54 PM, Tao Mao <yiyeguhu at gmail.com> wrote:
>
>> You are almost correct: this throughput number is defined as the ratio of
>> user application time to the total run time, i.e., 100% is the "ideal"
>>
>> From your reporting, ~97% is the best result so far. It's near the limit.
>> If you don't have a particular reason to push further, you can walk away
>> with your current tuning. Can you post the JVM options for your best run?
>>
>> Thanks.
>> Tao Mao
>>
>>
>> On Mon, Aug 24, 2015 at 12:28 PM, D vd Reddy <dvdeepankar.reddy at gmail.com
>> > wrote:
>>
>>> This is the number given out by GCViewer, it is the ratio of time spent
>>> in GC to total time of the JVM running.
>>>
>>>
>>>
>>>
>>> Thanks
>>>
>>>
>>> On Mon, Aug 24, 2015 at 12:15 PM, Yu Zhang <yu.zhang at oracle.com> wrote:
>>>
>>>> Reddy,
>>>>
>>>> Can you explain how you measure the throughput? For example, what does
>>>> it mean 'throughput of 92%'?
>>>>
>>>> Thanks,
>>>> Jenny
>>>>
>>>> On 8/24/2015 12:05 PM, D vd Reddy wrote:
>>>>
>>>> I made a couple of experiments run over the weekend, first I ran a
>>>> experiment with lowering the maxGCPause it did help, lowered the throughput
>>>> to 92%.
>>>>
>>>>
>>>>
>>>
>>
>
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