[9] RFR (XS): 8157560: Reserve space for allocation prefetch only in builds that support allocation prefetching

[Vladimir Kozlov]

Looks good.

thanks,
Vladimir

On 5/23/16 4:00 AM, Zoltán Majó wrote:
> Hi,
>
>
> please review the path for 8157560.
>
> https://bugs.openjdk.java.net/browse/JDK-8157560
>
> Problem: Every thread-local allocation buffer (TLAB) contains a reserved
> area to accommodate allocation prefetches (i.e., to make sure that
> instructions performing allocation prefetch do not cause faults). The
> reserved area is at the end of the TLAB.
>
> Currently, all the reserved area is created in all builds, even though
> only the C2 compiler generates allocation prefetches. As a result, in
> builds without C2, some heap space is wasted at the end of each TLAB.
> Creating the reserved area also causes problems for internal testing of
> the AllocatePrefetchLines/AllocateInstancePrefetchLines command-line flags.
>
> Solution: Create the reserved area only in C2-enabled builds. Re-enable
> testing of the AllocatePrefetchLines/AllocateInstancePrefetchLines flags.
>
> Webrev:
> http://cr.openjdk.java.net/~zmajo/8157560/webrev.00/
>
> Testing:
> - JPRT;
> - pre-PIT RBT in progress;
> - internal tests -- all pass.
>
> I plan to push the fix directly into hs as testing of
> AllocatePrefetchLines/AllocateInstancePrefetchLines is disabled only in hs.
>
> Thank you!
>
> Best regards,
>
>
> Zoltan
>