Seeking answer to a GC pattern

[Srinivas Ramakrishna]

Use -XX:MaxTenuringThreshold=2 and you might see better behavior that
+AlwaysTenure (which is almost always a very bad choice). That will at
least reduce some of the nepotism issues from +AlwaysTenure that Thomas
mentions. MTT > 2 is unlikely to help at your current frequency of minor
collections since the mortality after age 1 is fairly low (from your
tenuring distribution). Worth a quick test.

-- ramki

On Mon, Oct 26, 2015 at 12:33 PM, Jun Zhuang <jun.zhuang at hobsons.com> 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 <513-746-2288> (work)*
>
> *513-227-7643 <513-227-7643> (mobile)*
>
>
>
> _______________________________________________
> hotspot-gc-use mailing list
> hotspot-gc-use at openjdk.java.net
> http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use
>
>
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