RFR(L): 8195098: Low latency hashtable for read-mostly scenarios

[Robbin Ehn]

On 05/03/2018 11:42 AM, David Holmes wrote:
> On 3/05/2018 7:30 PM, Robbin Ehn wrote:
>> Hi all,
>>
>> After feedback from DavidH (volatile) here is an update:
>> Inc:
>> http://cr.openjdk.java.net/~rehn/8195098/v2/inc/webrev/
> 
> Looks fine. Thanks.

Thanks David!

/Robbin

> 
> David
> -----
> 
>> Full:
>> http://cr.openjdk.java.net/~rehn/8195098/v2/full/webrev/
>>
>> Thanks!
>>
>> /Robbin
>>
>> On 05/02/2018 11:03 AM, Robbin Ehn wrote:
>>> Hi all,
>>>
>>> Here is an update with Gerard's and Coleen's input.
>>>
>>> Inc:
>>> http://cr.openjdk.java.net/~rehn/8195098/v1/inc/webrev/
>>> Full:
>>> http://cr.openjdk.java.net/~rehn/8195098/v1/full/webrev/
>>>
>>> Thanks, Robbin
>>>
>>> On 2018-04-26 09:38, Robbin Ehn wrote:
>>>>
>>>> Hi all, please review.
>>>>
>>>> The lower latency of the new gcs have higher demands on runtime data-structure
>>>> in terms of latency. This is a concurrent hashtable using the global-counter
>>>> (8195099).
>>>>
>>>> Webrev:
>>>> http://cr.openjdk.java.net/~rehn/8195098/v0/webrev/
>>>>
>>>> Bug:
>>>> https://bugs.openjdk.java.net/browse/JDK-8195098
>>>>
>>>> * Readers never blocks or spins.
>>>> * Inserts do CAS from a read-side, need to re-CAS during re-size/deletion in 
>>>> targeted bucket or insert collision. (inserts are conceptually a reader)
>>>> * Deletes locks the targeted bucket, all other buckets are free for operations.
>>>> * Re-size locks one bucket at the time, all other buckets are free for 
>>>> operations.
>>>>
>>>> It does concurrent re-size by doubling size and use one more bit from hash.
>>>> That means a bucket in the old table contains nodes to either one of two 
>>>> buckets
>>>> in the new table. Each node in the chain is sorted into one of the two buckets
>>>> with concurrent readers. Shrinking just take two node chains and put them
>>>> together in the corresponding bucket. To keep track of what is visible to the
>>>> concurrent readers it's uses a global-counter, needed during re-size and for
>>>> deletes.
>>>>
>>>> A gtest is provided which passes on our platforms, we also have a prototype 
>>>> of the stringtable using this which passes tier 1-5 on our platforms.
>>>>
>>>> Various people have pre-reviewed various parts, thanks! And a special thanks to
>>>> Coleen for a lot of reviewing!
>>>>
>>>> Thanks, Robbin