RFR: JDK-8262068: Improve G1 Full GC by skipping compaction for regions with high survival ratio [v8]

[Hamlin]

在 2021/3/12 16:12, Thomas Schatzl 写道:
> Hi,
>
> On 12.03.21 06:13, Hamlin Li wrote:
>> On Thu, 11 Mar 2021 15:19:36 GMT, Thomas Schatzl 
>> <tschatzl at openjdk.org> wrote:
>>
>>>> Hamlin Li has updated the pull request incrementally with one 
>>>> additional commit since the last revision:
>>>>
>>>>    fix bot crash.
>>>
>>> src/hotspot/share/gc/g1/g1FullGCMarker.hpp line 104:
>>>
>>>> 102:
>>>> 103:   void flush_mark_region_cache() {
>>>> 104:     if (MarkSweepDeadRatio > 0) {
>>>
>>> Drop this check to make the code more straightforward. Other code 
>>> like in PR #2579 might find this information useful too. Maybe this 
>>> could even be factored out in a separate CR.
>>
>> Hi Thomas,
>> Do you mean to collect liveness info in mark phase when G1 full gc, 
>> even if MarkSweepDeadRatio is == 0 (which means do not skip any 
>> regions when compaction)? If this is the request, I can file a new 
>> bug for this liveness collection in G1 full gc.
>
> Yes, please split out the liveness info gathering in the mark phase 
> into a separate CR. This is what PR #2579 needs.
> StefanJ and me were discussing adding this already when implementing 
> the G1 parallel full gc, but due to lack of users we refrained from 
> that..
>
Thanks for confirmation, I have created the issue: 
https://bugs.openjdk.java.net/browse/JDK-8263495.

>> For the jfr PR #2579 , I think it's can be addressed in a separate 
>> bug which depends on the one for liveness collection.
>> I will file/work these 2 new bugs (liveness collection when g1 full 
>> gc, jfr liveness event after full gc) if this is what you suggested.
>
> PR #2579 is about the JFR liveness event. Jbachorik (the author of 
> that PR) could just reuse the information gathered in that new CR 
> then. Please coordinate with him if needed, but I do not think you 
> specifically needs to worry about the JFR event, I assume that 
> jbachorik will likely be happy to be able to add the plumbing for the 
> JFR event then.
>
> I cc'ed him (using some email address from the jfr-dev mailing list, I 
> hope I got it right).

Got it. Just let me know if any assitant is needed from me.

Thanks,

- Hamlin

>
> Thanks,
>   Thomas