(new patch) RFR(s): 8213791: StringTable: Use get and insert

[Robbin Ehn]

Hi Gerard,

On 2018-11-26 18:40, Gerard Ziemski wrote:
> Looks good.

Thanks!

> 
> Small nitpick: the usage of white space in “internal_get_insert” and “ internal_get” could be more consistent.

Fixed

> 
> Also, you say the performance is “different, not better or worse”, so I assume you mean no significant perf regressions (or benefit) to report?

Average in my benchmark is better but insignificant better. I see more expensive inserts while we do concurrent 
cleaning, when not faster.

> 
> P.S. I created a clone JDK-8214310 to do the same for the SymbolTable.
> 

Great!

/Robbin

> 
> cheers
> 
>> On Nov 20, 2018, at 7:43 AM, Robbin Ehn <robbin.ehn at oracle.com> wrote:
>>
>> Hi all, please review.
>>
>> Webrev:
>> http://cr.openjdk.java.net/~rehn/8213791/webrev/
>>
>> CR:
>> https://bugs.openjdk.java.net/browse/JDK-8213791
>>
>> I created an plain(:er) insert which always allocate the Node outside.
>> This makes the critical section shorter, which is good for overall performance.
>> But a bit slower in the contended bucket case.
>> So performance is different, not better or worse.
>>
>> If we can move SymbolTable to the same logic, we can remove the get_insert.
>>
>> Stress test stringtable, t1-3 and gtests passes.
>>
>> Thanks, Robbin
>>
>> On 11/13/18 6:21 PM, Robbin Ehn wrote:
>>> Hi all, please review.
>>> It's problematic with allocating inside a critical section.
>>> - You are not allowed to safepoint.
>>> - Allocate cannot use GlobalCounter write side for lock free allocations.
>>> - Easy to accidentally create deadlocks.
>>> This patch moves the allocation for oopStorage outside the hashtable.
>>> Performance is unaffected, if you don't hammer StringTable with multiple threads
>>> using identical strings.
>>> This is just a first small step, mainly for not limiting oopStorage.
>>> Webrev:
>>> http://cr.openjdk.java.net/~rehn/8213791/webrev/
>>> CR:
>>> https://bugs.openjdk.java.net/browse/JDK-8213791
>>> Parent CR: ConcurrentHashTable: Do not allocate inside critical section
>>> https://bugs.openjdk.java.net/browse/JDK-8209054
>>> Passes t1-3, multiple thread same string intern manual test and jmh stress test.
>>> Thanks, Robbin
>