On Fri, 2 Apr 2021 23:12:21 GMT, Anthony Scarpino <ascarp...@openjdk.org> wrote:
>> According to SO, unsynchronized writes to a map can lead to lock up, see >> here: >> https://stackoverflow.com/a/1003237 >> Or here: >> https://mailinator.blogspot.com/2009/06/beautiful-race-condition.html?m=1 >> What's the performance impact of adding synchronization on the hash map only? > > Ok, thanks for pointing that out, I didn't realize that limitation. However > using synchronizedMap is overkill as it locks every operation. As I read it, > only structural changes like adding and removing keys from the map causes > problems. Getting a value from the map does not. Therefore I would only > need to synchronize the putIfAbsent() at 449, which is pretty minor. The > expunging of the map is already synchronized in WeakHashMap. > > The original code was half the performance of this one. If you synchronize `putIfAbsent` but not `get` you'll still get the possible infinite loop described in the SO post. ------------- PR: https://git.openjdk.java.net/jdk/pull/3296
