RFR(xs): 8134749: SoftReferences declared dead too early
tom.benson at oracle.com
Mon Aug 31 18:27:13 UTC 2015
Also looks good to me. I actually picked up both your changes, on the
off chance it might help with 8130261. (That appears it may be a
problem with 'last ditch' GCs, which free all soft refs. Yes, a
longshot, but I tried it anyway. No help.)
On 8/31/2015 2:20 PM, Jon Masamitsu wrote:
> Change looks good.
> Could you please run some tests with your fix and
> -XX:+UseDynamicNumberOfGCThreads and
> -XX:+UseParallelGC threads? UseDynamicNumberOfGCThreads sometimes moves
> work among the queues to get them into queues that will be processed
> by an active
> GC worker. Thanks.
> On 08/31/2015 07:15 AM, Per Liden wrote:
>> While preparing a different patch I looked through the
>> ReferenceProcessor and noticed what looks like a silent mistreatment
>> of SoftReferences.
>> Summary: RefProcPhase1Task uses WorkerThread::id() to select the list
>> to process. After the recent changes to how WorkGang works, this
>> no longer guarantees that all reference lists are processed. This in
>> turn means we might kill SoftReferences even when the policy says
>> they should be kept alive.
>> The fix here would be to use the worker_id (named "i" in this code)
>> passed into the Task's work() function instead of using
>>  There's no longer any guarantee that all GangWorker threads will
>> execute the Task's work() function, since a quick-to-wakeup worker
>> thread might steal the work intended for a slow-to-wakeup worker thread.
>> Webrev: http://cr.openjdk.java.net/~pliden/8134749/webrev.0/
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8134749
>> Testing: jprt
>> Btw, I'll to send out a follow-up patch (JDK-8134744) which makes
>> sure WorkerThread::id() and the worker_id always match to avoid this
>> type of bugs in the future.
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