On 04/21/2016 06:07 PM, Peter Levart wrote:
I propose to add a thread-safe WeakPairMap data structure which
associates a pair of weakly-reachable keys with a strongly-reachable
value based on ConcurrentHashMap. Such data structure is
footprint-friendly, since only a single instance exists for a
particular purpose, totaling 3 instances for the transient structures
serving all Modules in the system:
http://cr.openjdk.java.net/~plevart/jdk9-dev/Module.WeakSet.multithreadUnsafe/webrev.01/
Oops...
It looks like I replaced one thread-unsafe construction with another one:
389 // additional exports added at run-time
390 // source module (1st key), target module (2nd key), exported
packages (value)
391 private static final WeakPairMap<Module, Module, Set<String>>
transientExports =
392 new WeakPairMap<>();
...that would've been OK if I hadn't used normal HashSet for holding the
set of packages:
623 // add package name to transientExports if absent
624 transientExports
625 .computeIfAbsent(this, other, (_this, _other) -> new
HashSet<>())
626 .add(pn);
Luckily this can be easily fixed by using a ConcurrentHashMap instead of
HashSet which is even more space-friendly (HashSet is just a wrapper
around HashMap and HashMap is basically the same structure as
ConcurrentHashMap):
http://cr.openjdk.java.net/~plevart/jdk9-dev/Module.WeakSet.multithreadUnsafe/webrev.02/
Regards, Peter
