RFR: Trim the TLAB sizes to avoid wasteful retirement under TLAB races

[Roman Kennke]

Am 21.09.2017 um 12:19 schrieb Aleksey Shipilev:
> On 09/21/2017 12:15 PM, Roman Kennke wrote:
>> Am 21.09.2017 um 09:31 schrieb Aleksey Shipilev:
>>> On 09/20/2017 09:17 PM, Aleksey Shipilev wrote:
>>>> http://cr.openjdk.java.net/~shade/shenandoah/tlab-race-trim/webrev.01/
>>>>
>>>> This implements TLAB trimming to avoid wasteful retirement. The rationale is given in the comment
>>>> right in the code. It does not seem to make allocation significantly more costly. To make it less
>>>> overheady, changed the counter update code to be called on new region issuance, not on TLAB
>>>> issuance.
>>> Added more discussion:
>>>     http://cr.openjdk.java.net/~shade/shenandoah/tlab-race-trim/webrev.02/
>>>
>>> -Aleksey
>>>
>> The number 8 is hardwired. Does this make sense? Should we allow this to be configured, if only for
>> our own experimentation?
> Well, it could be experimental -- which requires winding up argument checking logic and tests -- but
> I would really like to move on already :) We can turn it experimental if there is interest later,
> but I don't see any interest right now.
>
> -Aleksey
>
Ok then