LinearProbeHashtable <was> Re: ClassValue perf?

[Paul Sandoz]

Hi Peter,

> On 27 May 2016, at 12:41, Peter Levart <peter.levart at gmail.com> wrote:
> 
> Hi Paul,
> 
> On 05/26/2016 01:20 PM, Paul Sandoz wrote:
>> Hi Peter,
>> 
>> Opportunistically if your LinearProbeHashtable works out then i am wondering if we could replace the use of CHM within MethodType.ConcurrentWeakInternSet, which only uses get/putIfAbsent/remove.
>> 
>> Thereby CHM can use VarHandles without inducing a circular dependency.
>> 
>> Paul.
> 
> It could be used, yes. LinearProbeHashtable is not scalable to multiple threads like CHM is for modifications as it is using a single lock for all modification operations including rehashing, but it is lock-free for lookups, so for usecases such as caching, where lookups dominate and modifications are mostly performed in batches from single thread (when some subsystem initializes), it could be a viable alternative to CHM.
> 

Or say expunging of stale entries?


> If it is moved to some jdk.internal subpackage and made public, I could add missing Map methods, mostly to be able to include it in MOAT tests.
> 
> What do you think?
> 

I think moving to say jdk.internal.util.concurrent makes sense. Keeping it lean and focused to the purpose it currently serves seems appropriate, so implementing Map might an unwanted embellishment, i would be inclined to write some focused tests and also leverage the contextual testing via it’s use within ClassValue (and maybe MethodType).

I should investigate updating MethodType and running the Octane benchmark...

Paul.
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