JEP 270: Reserved Stack Areas for Critical Sections

[Volker Simonis]

Hi,

that's an interesting JEP. Thanks a lot for the detailed analysis and
problem description.

I see a little problem with the additional zone you want to introduce.
This zone must be page-size aligned and at least one page. But on
PowerPC it is not uncommon nowadays that Linux runs with a default
page size of 64K. Wasting another page for the new zone would result
in 3*64K = 192K overhead for the three zones. Not sure about other
architectures but it seems that at least AArch64 supports a 64K
default page size as well. Itanium even has two stacks (register and
memory) which doubles the trouble.

Taking all this into account, have you considered using a part of the
available yellow zom as reserved stack are for critical sections? If
you run with a page size of 4K you could just increase the yellow zone
by the required number of pages, otherwise you could just use it as is
(64K should be enough for a critical section according your analysis.

We must also somehow ensure that critical sections can not call
arbitrary user code, otherwise the stack usage of the critical section
will be unbound. Did you use some kind of static analysis tools to
check for this?

Thank you and best regards,
Volker

On Thu, Sep 24, 2015 at 2:25 AM,  <mark.reinhold at oracle.com> wrote:
> New JEP Candidate: http://openjdk.java.net/jeps/270
>
> - Mark