Request for reviews (M): 7079329: Adjust allocation prefetching for T4

[Christian Thalinger]

Looks good.

-- Christian

On Aug 16, 2011, at 7:05 PM, Vladimir Kozlov wrote:

> Thank you, Christian, Paul and Igor
> 
> I updated webrev with suggestions:
> 
> http://cr.openjdk.java.net/~kvn/7079329/webrev
> 
> - AllocateInstPrefetchLines renamed to AllocateInstancePrefetchLines.
> - Prefetch instructions in x86 .ad use MacroAssembler instructions.
> - Added Abstract_VM_Version::reserve_for_allocation_prefetch() method used in ThreadLocalAllocBuffer::end_reserve().
> - I have to use FLAG_SET_ERGO() for AllocatePrefetchLines*2 setting since VM_Version::initialize() is called twice on Sparc (long story which I don't want to discuss here).
> 
> Vladimir
> 
> Vladimir Kozlov wrote:
>> I will think about it.
>> Thanks,
>> Vladimir
>> On 8/16/11 6:11 AM, Paul Hohensee wrote:
>>> Also, is there a way to avoid using #ifdef SPARC in threadLocalAllocBuffer.hpp?
>>> Maybe add a predicate to vm_version that says whether or not to play the tlab
>>> reserve game.
>>> 
>>> Paul
>>> 
>>> On 8/16/11 9:01 AM, Paul Hohensee wrote:
>>>> You're changing the meaning of an existing flag, AllocatePrefetchLines, to
>>>> apply only to arrays, right?
>>>> 
>>>> If so, I'd add another flag for arrays, maybe call it AllocateArrayPrefetchLines,
>>>> and change the code so AllocatePrefetchLines becomes an optional parameter.
>>>> E.g., default it to -1 in globals.hpp, and if it's specified on the command line,
>>>> set both AllocateArrayPrefetchLines and AllocateInstPrefetchLines to the
>>>> command line value. That would retain backward compatibility: I remember
>>>> seeing AllocatePrefetchLines used in a few jbb submissions.
>>>> 
>>>> Also, I'd rename AllocateInstPrefetchLines to AllocateInstancePrefetchLines. 'Inst"
>>>> is a bit confusing to me and perhaps to others: the first thing I think of is 'instruction'.
>>>> 
>>>> Paul
>>>> 
>>>> On 8/15/11 9:12 PM, Vladimir Kozlov wrote:
>>>>> http://cr.openjdk.java.net/~kvn/7079329/webrev
>>>>> 
>>>>> 7079329: Adjust allocation prefetching for T4
>>>>> 
>>>>> L2 cache line size is 32 bytes on T4 instead of 64 bytes on T series before. As result BIS instruction prefetches
>>>>> only 32 bytes. Jbb2005 runs show that prefetching 64 bytes is still better on T4 so 2 BIS instructions should be issued.
>>>>> 
>>>>> BIS can't be use for general prefetching since it may fault. New PrefetchAllocation node was added for allocation
>>>>> prefetching.
>>>>> 
>>>>> Changed prefetchAlloc_bis parameter from memory to regP.
>>>>> 
>>>>> Use AllocatePrefetchInstr on Sparc to allow specify what instruction to use for allocation prefetching (0: prefetch
>>>>> write, 1: BIS).
>>>>> 
>>>>> Added new instructions on Sparc cacheLineAdrX to reduce number of instructions generated for finding next cache line
>>>>> address.
>>>>> 
>>>>> Added new flag AllocateInstPrefetchLines to specify number of lines to prefetch for instance allocation.
>>>>> 
>>>>> L1_data_cache_line_size() renamed to prefetch_data_size().