RFR (S): 8147910: Cache initial active_processor_count

[David Holmes]

Hi Thomas,

Thanks again for taking this on.

On 22/07/2016 9:36 PM, Thomas Schatzl wrote:
> Hi all,
>
>   can I have reviews for this tiny change that adds an API to set the
> initial active processor count at startup? It also adds that count to
> the hs_err log file.
>
> It is required to fix JDK-8161993.
>
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8147910
>
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8147910/webrev/

src/share/vm/runtime/os.hpp

Nit: can you change update_initial_active_processor_count() to 
initialize_initial_active_processor_count() please - otherwise it gives 
the impression that it can be called many times to update the value.

+     guarantee(_initial_active_processor_count > 0, "Initial active 
processor count not set yet.")

An assert will suffice here.

---

src/share/vm/runtime/os.cpp:

!   // We access the raw value here because using the accessor will let 
its guarantee
!   // fail if the crash occurs before initialization of this value.
!   st->print(" (initial active %d)", _initial_active_processor_count);

Good point! Did you find that out the hard way? :)

I wonder if we should clarify the message in that case:

(initial active %d - zero if not yet set)

?

Thanks,
David

> Testing:
> jprt, checking generated hs_err files using tasksel
>
> Thanks,
>   Thomas
>