RFC 8299037 Make UseContainerCpuShares true by default for JDK 8u 11u 17u

[Severin Gehwolf]

Thanks for starting this conversation, Ioi!

On Mon, 2022-12-19 at 09:30 -0800, Ioi Lam wrote:
>  When JDK-8281181 was backported to 17u and 11u, some users reported
> that their containerized workload experienced OOM.
>  
>  Although the fix in JDK-8281181 is technically "correct" as CPU
> shares shouldn't be used to express a limit (see discussion in the
> CSR JDK-8281571), unfortunately some workload had been configured
> that way due to how the JDK historically mis-interpreted CPU shares.
>  
>  Introducing a significant behavioral change in an update release
> probably isn't a good idea.
>  
>  The proposal is to change the default value of UseContainerCpuShares
> from true to false, so users of update releases up to 17u will need
> to opt into the new behavior.

+1

Provided this will be the way we go, it would require a new CSR, right?

>  In the next LTS release, the UseContainerCpuShares flag will have no
> effect. The new behavior will always be used.
>  
>  (PS, since UseContainerCpuShares has been removed in JDK 21, we may
> need to add it back as an obsolete flag to ease the transition from
> 17u to 21).

Yes, a decision would have to be made about this for JDK 21. We need
some data as to what uses cases are out there which make re-introducing
cpu shares compelling, though.

Thanks,
Severin