[9] RFR (XS): C2: continuous CallSite relinkage eventually disables compilation for a method

[dean.long at oracle.com]

Are there any other uses of next_alive() where we would want something 
more strict like next_entrant()?  If so then it might be worth it to add 
this to the iterator.

dl


On 1/30/17 5:10 AM, Vladimir Ivanov wrote:
> Are people fine with the following version?
>
>   http://cr.openjdk.java.net/~vlivanov/8173338/webrev.03/
>
> Otherwise, I'll file a separate RFE for 
> CodeCache::make_marked_nmethods_not_entrant() part.
>
> Best regards,
> Vladimir Ivanov
>
> On 1/27/17 11:11 PM, Vladimir Ivanov wrote:
>>>> I don't see how method::_code is relevant to compiled method state
>>>> checks. It's just a double-checked locking idiom. Should be safe since
>>>> state transitions are monotonic.
>>>>
>>>
>>> I think there is a path where AOT methods can become in-use again, so
>>> it's not completely monotonic.
>>
>> Ok, I can leave the pre-lock check only for nmethods.
>>
>> Best regards,
>> Vladimir Ivanov
>>
>>>>> But, I think, it should be safe with your original change in
>>>>> CodeCache::make_marked_nmethods_not_entrant() because it does not
>>>>> access
>>>>> method::_code. You should use !is_not_entrant() instead of 
>>>>> is_alive() -
>>>>> it works for AOT too.
>>>>
>>>> I decided to keep state checks both in
>>>> CodeCache::make_marked_nmethods_not_entrant() and
>>>> nmethod::make_not_entrant_or_zombie(). !is_not_entrant() isn't precise
>>>> enough, since it passes for zombie nmethods as well.
>>>>
>>>> Also, added equivalent pre-lock check in
>>>> AOTCompiledMethod::make_not_entrant_helper(). Let me know if you see
>>>> any problems with that.
>>>>
>>>> Best regards,
>>>> Vladimir Ivanov
>>>>
>>>>> On 1/26/17 12:44 PM, Vladimir Ivanov wrote:
>>>>>> What about moving the check to nmethod::make_not_entrant()?
>>>>>>
>>>>>> http://cr.openjdk.java.net/~vlivanov/8173338/webrev.01
>>>>>>
>>>>>> Or I can fix it separately.
>>>>>>
>>>>>> Best regards,
>>>>>> Vladimir Ivanov
>>>>>>
>>>>>> On 1/26/17 11:30 PM, Vladimir Kozlov wrote:
>>>>>>> It will not work for AOT nmethods which have not_used state.
>>>>>>>
>>>>>>> Vladimir
>>>>>>>
>>>>>>> On 1/26/17 8:47 AM, Vladimir Ivanov wrote:
>>>>>>>> http://cr.openjdk.java.net/~vlivanov/8173338/webrev.00/
>>>>>>>> https://bugs.openjdk.java.net/browse/JDK-8173338
>>>>>>>>
>>>>>>>> The fix for JDK-7177745 disabled deoptimization count update 
>>>>>>>> when it
>>>>>>>> happens due to CallSite.target change.
>>>>>>>>
>>>>>>>> There was one case missed though: the count is still updated when
>>>>>>>> compilation fails due to a dependency becoming invalid
>>>>>>>> during the compilation.
>>>>>>>>
>>>>>>>> The fix is to avoid the update when recompilation fails due to
>>>>>>>> call_site_target dependency failure.
>>>>>>>>
>>>>>>>> Also, added a check in 
>>>>>>>> CodeCache::make_marked_nmethods_not_entrant()
>>>>>>>> to avoid repeated nmethod::make_not_entrant() calls
>>>>>>>> on nmethods which are already not entrant. Otherwise, the check is
>>>>>>>> performed under Patching_lock inside
>>>>>>>> nmethod::make_not_entrant_or_zombie() for every non-entrant
>>>>>>>> method in
>>>>>>>> the code cache.
>>>>>>>>
>>>>>>>> Testing: regression test, RBT (in progress)
>>>>>>>>
>>>>>>>> Thanks!
>>>>>>>>
>>>>>>>> Best regards,
>>>>>>>> Vladimir Ivanov
>>>