Remove the experimental option UseCGroupMemoryLimitForHeap?

[Severin Gehwolf]

On Mon, 2019-12-16 at 10:26 +0000, linzang(臧琳) wrote:
> Dear All,
>                 I would like to discuss with you whether the experimental option “UseCGroupMemoryLimitForHeap” is unnecessary now?
>                 I see there is only one place in the code using this flag, and the logic there is considering cgroup memory limit when calculating heap size, but it is duplicated with os::physical_memory() since there is same implementation for container support.
>                 So is it ok if I remove this flag?

It would be a compatibility concern. There are users out there which
still use it. So we cannot just remove the flag and fail the VM startup
if provided.

Perhaps removal of code in Arguments::set_heap_size like done for JDK
11 in JDK-8194086, but still accepting the VM option could be a
possibility. Perhaps also printinting a warning that the option does
nothing along the way would be good to.

It depends what you have in mind, but it seems - unless there is a good
reason - it would be wiser to leave that code as-is.

Thanks,
Severin