RFR (S): JEP-142: Reduce Cache Contention on Specified Fields

[Kirk Pepperdine]

Actually, sun.misc.Contended right beside sun.misc.Unsafe doesn't sound like such a bad idea.

-- Kirk

On 2012-11-26, at 8:08 PM, Doug Lea <dl at cs.oswego.edu> wrote:

> On 11/26/12 13:40, Aleksey Shipilev wrote:
>> On 11/26/2012 09:35 PM, Remi Forax wrote:
>>> On 11/26/2012 05:44 PM, Aleksey Shipilev wrote:
>>>> On 11/26/2012 08:22 PM, Doug Lea wrote:
>>>>> One small suggestion to slightly appease the nanny-state folks.
>>>>> How about burying the annotation one lever deeper to
>>>>> java.util.concurrent.atomic.
>>> 
>>> +1
>>> 
>> 
>> Still fail to see the rationale about this.
> 
> All things considered, I'm back to agreeing with you --
> Just j.u.c.Contended
> 
>> 
>>> I think you should re-write the javadoc ...
> 
> The Contended.java file and its javadoc in Aleksey's webrev is just a
> placeholder to get things moving. We expect to solicit
> reviews in the usual way (mainly on concurrency-interest list)
> for a version that will make it into JDK8.
> 
>> 
>> I.e.
>> 
>>     @Contended
>>     public class ValueClass {
>>          private int field1;
>>          private int field2;
>>          private int field3;
>>          private int field4;
>>     }
>> 
>> is the shortcut for:
>> 
>>     public class ValueClass {
>>          @Contended("theSame") private int field1;
>>          @Contended("theSame") private int field2;
>>          @Contended("theSame") private int field3;
>>          @Contended("theSame") private int field4;
>>     }
>> 
>> That is, all the fields would be densely-packed, but will be padded as
>> the group. Note that it is not the same as:
>> 
>>     public class ValueClass {
>>          @Contended private int field1;
>>          @Contended private int field2;
>>          @Contended private int field3;
>>          @Contended private int field4;
>>     }
>> 
>> Maybe that is already confusing enough to drop class-level annotation?
>> What do others feel about this?
> 
> I think that the most common and most-recommended case will be class-level,
> so it should be kept. We can work on the usage advice in the javadocs.
> 
> -Doug
> 
>