[9] RFR(XS): 8153292: AllocateInstancePrefetchLines>AllocatePrefetchLines can trigger out-of-heap prefetching

[Vladimir Kozlov]

Looks good.

Thanks,
Vladimir

On 4/20/16 8:01 AM, Zoltán Majó wrote:
> Hi,
>
>
> please review the patch for 8153292.
>
> https://bugs.openjdk.java.net/browse/JDK-8153292
>
>
> Problem: To avoid out-of-heap accesses by instructions prefetching data,
> TLABs have a reserved area. The size of that area is supposed to be
> large enough to accommodate possible prefetching.
>
> The amount of prefetched data is controlled separately for instance and
> array allocations (by the AllocateInstancePrefetchLines and
> AllocatePrefetchLines flags). The size of the reserved area in the TLAB
> is, however, determined only based on AllocatePrefetchLines. As a
> result, AllocateInstancePrefetchLines > AllocatePrefetchLines can
> trigger out-of-heap memory accesses.
>
>
> Solution: Set the size of the reserved TLAB area to the MAX of both flags.
>
> Webrev:
> http://cr.openjdk.java.net/~zmajo/8153292/webrev.00/
>
> Testing:
> - JPRT;
> - local testing on a solaris_sparc machine.
>
> Thank you!
>
> Best regards,
>
>
> Zoltan
>