Deciding between 2MB or 32MB region size in G1

[Amit Balode]

Yeah, humongous allocation savings is a bigger advantage to have as
compared to some amount of fragmentation which will come with larger 32MB.

Would love to hear more comments.

On Thu, Feb 2, 2017 at 9:50 PM, yu.zhang at oracle.com <yu.zhang at oracle.com>
wrote:

> Hi, Amit,
>
> IMO, there is no one size fits all.
>
> Some considerations about the bigger region size:
>
> Reduce the humongous objects. The humongous objects are allocated in old
> gen. If they can not be collected during young gc, they can fill up the old
> gen quickly without marking or full gc.
>
> Less remember set to keep track of.
>
> Bigger TLAB. This could be good or bad. With bigger tlab, threads need
> less refill trip, but may waste more tlab space. It depends on the objects
> size.
>
> Possible bigger waste due to humongous objects (depends on the size of the
> objects)
>
> Possible end of region waste for allocation.
>
> Maybe others have more comments.
>
> Thanks
>
> Jenny
>
> On 02/01/2017 05:54 AM, Amit Balode wrote:
>
> Hello, We have multiple applications running in production where
> predicting size of the runtime object is kinda tough and random. It could
> vary from 1KB to 25MB for different applications. To not have too many
> lingering configs for different applications, I am trying to come up with
> standard set of configs which could be applicable to all applications. Some
> applications do not exceed 10KB object size, so I could definitely keep 2MB
> as region size for them. But I am wondering what would be disadvantage of
> setting all applications to 32MB region size regardless of how small the
> object is?
>
> Is it that fragmentation issues will happen more if you have less regions?
> If so, will the fragmentation issue happen only during humongous
> allocations?
> In term of performance, will selection of size change anything?
>
> --
> Thanks & Regards,
> Amit.Balode
>
>
>
> _______________________________________________
> hotspot-gc-use mailing listhotspot-gc-use at openjdk.java.nethttp://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use
>
>
>


-- 
Thanks & Regards,
Amit.Balode
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.openjdk.java.net/pipermail/hotspot-gc-use/attachments/20170203/b7206f69/attachment.html>