Seeking answer to a GC pattern

[Yu Zhang]

Jun,

Sorry for the late response.
It seems you are disabling the gc ergonomic. Can you explain why? Do you 
need very low pause time? If you have a gc log, that would be helpful as 
well.

Thanks,
Jenny

On 10/26/2015 12:33 PM, Jun Zhuang wrote:
>
> Hi,
>
> When running performance testing for a java web service running on 
> JBOSS, I observed a clear saw-tooth pattern in CPU utilization that 
> closely follows the GC cycles. see below:
>
> Java startup parameters used:
>
> -XX:+TieredCompilation -XX:+PrintTenuringDistribution -Xms2048m 
> -Xmx4096m -XX:MaxPermSize=256m -XX:NewSize=128m -XX:MaxNewSize=128m 
> -XX:SurvivorRatio=126 -XX:-UseAdaptiveSizePolicy 
> -XX:+DisableExplicitGC -XX:+AlwaysTenure
>
> With this set of parameters, the young GC pause time ranged from 0.02 
> to 0.25 secs. When I used 256m for the young gen, the young GC pause 
> time ranged from 0.02 to 0.5 secs. My understanding is that the young 
> GC pause time normally stays fairly stable, I have spent quite some 
> time researching but have yet to find an answer to this behavior. I 
> wonder if people in this distribution list can help me out?
>
> *_Other related info_*
>
> * Server Specs: VM with 4 CPUs and 8 Gb mem
>
> * Test setup:
>
> ·# of Vusers: 100
>
> ·Ramp up: 10 mins
>
> ·Pacing: 5 – 7 secs
>
> * I tried with all other available GC algorithms, tenuring thresholds, 
> various sizes of the generations, but the AlwaysTenure parameter seems 
> to work the best so far.
>
> Any input will be highly appreciated.
>
> Sincerely yours,
>
> *//*
>
> */Jun Zhuang/**//*
>
> /Sr. Performance QA Engineer | Hobsons///
>
> /513-746-2288 (work)///
>
> /513-227-7643 (mobile)///
>
>
>
> _______________________________________________
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> hotspot-gc-use at openjdk.java.net
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