RFR: 8225035: Thread stack size issue caused by large TLS size

[Jiangli Zhou]

On Thu, Jun 27, 2019 at 12:57 AM Florian Weimer <fweimer at redhat.com> wrote:
>
> * Thomas Stüfe:
>
> >> I think
> >>
> >>   stack_adjust_size += guard_size;
> >>
> >> is redundant with the get_minstack-based adjustment because it is either
> >> included in it directly in the get_minstack value, or indirectly in the
> >> updated stack size computation in glibc (where it adds the guard size
> >> internally).
> >
> > Please do not change this!
> >
> > To me and I guess many others it is very important that nothing at all
> > changes if this workaround is off.
>
> That has already happened because recent glibc adds the guard size to
> the stack size internally now.
>
> But what I meant: only perform the += adjustment above for the
> !AdjustStackSizeForTLS case.

I'm reluctant to do that, because it adds additional dependencies on
the glibc implementation. Subtracting the non-TLS size from the value
returned by __pthread_get_minstack may not be forward compatible in
the future when __pthread_get_minstack changes. I agree with Thomas to
keep the workaround as simple as possible.

I think it is best to move forward with using __pthread_get_minstack
as is without binding too tightly to it's currently implementation
(subtracting the non-TLS values the function includes).

Best regards,
Jiangli

>
> >> I suspect this new flag is is working well because it effectively
> >> adds 20 KiB to all requested stack sizes (page size plus
> >> PTHREAD_MIN_STACK).  The static TLS size adjustment may not matter
> >> at all.  On older glibcs, the number is even higher because your
> >> code adds the guard size twice (once in __pthread_get_minstack, once
> >> in the Hotspot code).
> >
> > Which, again, would be an argument for a much simpler
> > "-XX:MinStackSize" option...
>
> Indeed.
>
> Thanks,
> Florian