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

[Tobias Hartmann]

Hi Zoltan,

looks good to me!

Best regards,
Tobias

On 20.04.2016 17:01, 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
>