RFR (M): JDK-8030177: G1: Enable TLAB resizing

[Bengt Rutisson]

Hi Thomas,

On 1/13/14 1:14 PM, Thomas Schatzl wrote:
> Hi,
>
> On Thu, 2014-01-09 at 20:32 +0100, Bengt Rutisson wrote:
>> Hi everyone,
>>
>> Can I have a couple of reviews for this change?
>>
>> http://cr.openjdk.java.net/~brutisso/8030177/webrev.00/
>>
>> https://bugs.openjdk.java.net/browse/JDK-8030177
>>
>> Unlike the other collectors G1 did not use dynamic sizes for the TLABs
>> that the Java threads use for allocation. That means that the TLABs
>> when using G1 were all fixed size and very small. This patch adds
>> dynamic sizing of TLABs to G1 too. In performance testing this has
>> shown a 2-3% improvement across a range of benchmarks.
>>
>> One difference compared to other collectors is that the maximum TLAB
>> size in G1 has to be limited by the region size and not by the eden
>> size. Also, for the other collectors the used space for TLAB
>> allocation was deducted from the maximum TLAB size because this was
>> essentially what was left in eden. That is an assumption that happened
>> to work out, but it kind of breaks the abstraction. So, the method
>> CollectedHeap:: tlab_used() has been added to be more consistent about
>> the TLAB abstraction and to make it more straight forward to implement
>> in G1.
> threadLocalAllocBuffer.cpp:
>
> line 83: typo:  allcoation -> allocation
>        // These allcoation should ideally not be counted but since it is
> not possible
>
> Looks good. It's okay for me to just fix this without a re-review ;-)

Thanks! I fixed the typo. :)

Bengt


>
> Thomas
>
>