[POSSIBLY SPAM: SPF] hotspot-gc-use Digest, Vol 143, Issue 1

[Stefan Reich]

Hi Thorsten!

Does MaxGCPauseMillis apply to System.gc() too? I thought this was for the
incremental collections.

> Did you parse gc logs or by hand/feel?

What, do you think I'm a beginner??? :D

Joke aside, yes it was just "by feel". I know I should measure it properly.
Is timing the call to System.gc() an acceptable way to measure this? As far
as I know, it only returns after GC has actually completed.

> If you are certain that you don't need more than 800mb of live objects,
limit the maxheap to something like 1.5 gb.

Hmm, I am rather not that certain about that... I'd like to keep the max
heap around 6 GB.


On Mon, 28 Jun 2021 at 09:35, Thorsten <tg at freigmbh.de> wrote:

> Hello,
>
> You should not get seconds long stop the world event. How did you measure
> the pauses? Did you parse gc logs or by hand/feel?
>
> The desired max pause for g1 can be tuned using
>
> -XX:MaxGCPauseMillis=200
>
> , so 200 ms max pause should be the default.
>
> It would be helpfull if you take gc logs and provide them. What java
> version are you using? In old java versions g1 is fairly bad, quality
> improves in newer versions.
>
> You can tune and change the garbage collector using -XX Options, see for
> example here
> https://ionutbalosin.com/2020/01/hotspot-jvm-performance-tuning-guidelines/
>
> Maybe you find one of the experimental garbage collectors helpfull for
> your application.
>
> Another simple "Hack" to tune your gc speed: If you are certain that you
> don't need more than 800mb of live objects, limit the maxheap to something
> like 1.5 gb. That way your app is simply unable to collect gigabytes of
> garbage and your max pauses will go down.
>
> Best regards,
>
> Thorsten
>
>
>
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>


-- 
Stefan Reich
BotCompany.de // Java-based operating systems
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