[9] RFR(L) 8013267 : move MemberNameTable from native code to Java heap, use to intern MemberNames

Peter Levart peter.levart at gmail.com
Tue Nov 11 19:30:10 UTC 2014

On 11/11/2014 07:58 PM, David Chase wrote:
> I’ve incorporated your other changes (not yet the linear-scan hash table) and will be retesting.
> One thing I wonder about for both hash table and binary search is if the first try should be attempted with no lock to avoid the overhead of synchronization; I expect that looking will be more common than interning, which in turn will be (vastly) more common than class redefinition.

Hi David,

Yes, that's why I implemented the hash table in a way where lookups are 
lock-free. Binary-search would be trickier to implement without locking, 
but maybe not impossible. Surely not with Arrays.binarySearch() but 
perhaps with a separate implementation. The problem with 
Arrays.binarySearch is that it returns an index. By the time you 
retrieve the element at that index, it can already move. I'm also not 
sure that "careful" concurrent insertion of new element would not break 
the correctness of binary search. But there is another way I showed 
before: using StampedLock. It is a kind of optimistic/pessimistic 
read-write lock. Its beauty is in that optimistic read part is almost 
free (just a volatile read at start and a readFence followed by another 
volatile read at the end). You just have to be sure that the algorithm 
guarded by an optimistic read lock terminates normally (that it doesn't 
spin in an endless loop or throw exceptions) in the presence of 
arbitrary concurrent modifications of looked-up state. Well, binary 
search is such an algorithm.

Regards, Peter

> David

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