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

[Vladimir Ivanov]

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
>>