RFR: Traveral GC heuristics

[Roman Kennke]

Am 24. Januar 2018 12:19:29 MEZ schrieb Aleksey Shipilev <shade at redhat.com>:
>On 01/24/2018 12:17 PM, Roman Kennke wrote:
>> Am 24.01.2018 um 12:14 schrieb Aleksey Shipilev:
>>> On 01/24/2018 12:12 PM, Roman Kennke wrote:
>>>> Am 24.01.2018 um 11:11 schrieb Aleksey Shipilev:
>>>>> On 01/23/2018 09:41 PM, Roman Kennke wrote:
>>>>>> Differential patch:
>>>>>> http://cr.openjdk.java.net/~rkennke/traversal/webrev.05.diff/
>>>>>> Full patch, including your changes:
>>>>>> http://cr.openjdk.java.net/~rkennke/traversal/webrev.05/
>>>>>
>>>>> Okay! This looks safe enough to push.
>>>>>
>>>>> I have a minor question about why this is needed:
>>>>>
>>>>> 1657     case _degenerated_outside_cycle:
>>>>> 1658       if (shenandoahPolicy()->can_do_traversal_gc()) {
>>>>> 1659         // Not possible to degenerate from here, upgrade to
>Full GC right away.
>>>>> 1660         cancel_concgc(GCCause::_allocation_failure);
>>>>> 1661         op_degenerated_fail();
>>>>> 1662         return;
>>>>> 1663       }
>>>>>
>>>>> Aren't we good with the usual Degenerated GC cycle here?
>>>>>
>>>>
>>>> The problem is that degen_outside_cycles goes into normal marking,
>and something's not up for that.
>>>> I'm hitting asserts when I go there.
>>>
>>> That probably indicates a bug? Traversal GC is ought to leave the
>heap in the state that is ready
>>> for the usual concurrent cycle, no?
>> 
>> In the middle of traversal GC? I don't know... Also, cannot, in any
>case, expect *concurrent* cycle
>> to work: we don't have the barriers for that. Theoretically, we could
>do STW normal cycle, but what
>> would be the point? I'd rather have a STW degen traversal pickup.
>
>"outside cycle" means you are out of Traversal GC already -- that means
>outside the *complete*
>cycle. So, here is where Traversal differs from Partial? Partial may be
>followed by the normal
>concurrent cycle, and Traversal can only run Traversals?

Yes, exactly. Traversal is not a minor GC like partial would be. It is much like normal concept GC.

-- 
Diese Nachricht wurde von meinem Android-Gerät mit K-9 Mail gesendet.