RFR(S/M): 8246476: remove AsyncDeflateIdleMonitors option and the safepoint based deflation mechanism

[Daniel D. Daugherty]

On 7/13/20 12:05 PM, Patricio Chilano wrote:
> Hi Dan,
>
> Changes look good to me!

Thanks!


> In synchronizer.cpp we have this comment about ObjectMonitor lifecycle:
>
> // Inflation unlinks monitors from om_list_globals._free_list or a 
> per-thread
> // free list and associates them with objects. Deflation -- which 
> occurs at
> // STW-time or asynchronously -- disassociates idle monitors from 
> objects.
> // Such scavenged monitors are returned to the 
> om_list_globals._free_list.
>
> With all the older code removed, are there still cases where we do 
> deflations at safepoint?

Good catch! I need to adjust that comment. I'll look for others also.

Dan


>
> Thanks!
> Patricio
> On 7/13/20 10:47 AM, Daniel D. Daugherty wrote:
>> Hi David,
>>
>> Thanks for the review!
>>
>> I need a second review folks... any takers?
>>
>> Dan
>>
>>
>> On 7/12/20 10:57 PM, David Holmes wrote:
>>> Hi Dan,
>>>
>>> This all looks good to me.
>>>
>>> Thanks,
>>> David
>>> -----
>>>
>>> On 8/07/2020 5:51 pm, David Holmes wrote:
>>>> On 8/07/2020 7:21 am, Daniel D. Daugherty wrote:
>>>>> Ping! Any takers??? Code deletion should be really appealing here!!
>>>>
>>>> Sorry Dan didn't get to it before vacation. But if you can wait 
>>>> till Monday ...
>>>>
>>>> Cheers,
>>>> David
>>>>
>>>>> Dan
>>>>>
>>>>>
>>>>> On 7/6/20 12:35 PM, Daniel D. Daugherty wrote:
>>>>>> Greetings,
>>>>>>
>>>>>> It's time to remove the AsyncDeflateIdleMonitors option from 
>>>>>> JDK16. We can
>>>>>> also get rid of the safepoint based deflation mechanism since 
>>>>>> turning off
>>>>>> async deflation (-XX:-AsyncDeflateIdleMonitors) was the only way 
>>>>>> left to
>>>>>> use it.
>>>>>>
>>>>>> This is marked as an "S/M" review because the number of 
>>>>>> touched/deleted
>>>>>> lines makes it a Medium review, but the number of touched/changed 
>>>>>> lines
>>>>>> (outside of the deletions) makes it a Small review. It's actually 
>>>>>> a pretty
>>>>>> fast read... :-)
>>>>>>
>>>>>> Here's the bug ID:
>>>>>>
>>>>>>     JDK-8246476 remove AsyncDeflateIdleMonitors option and the 
>>>>>> safepoint
>>>>>>                 based deflation mechanism
>>>>>>     https://bugs.openjdk.java.net/browse/JDK-8246476
>>>>>>
>>>>>> Here's the webrev URL:
>>>>>>
>>>>>> http://cr.openjdk.java.net/~dcubed/8246476-webrev/0_for_jdk16/
>>>>>>
>>>>>> The webrev is baselined on Thomas S's fix for 8248650 which is 
>>>>>> jdk-16+4
>>>>>> plus a dozen or so changesets.
>>>>>>
>>>>>> This change has been tested with Mach5 Tier[1-3],4,5,6,7,8 and 
>>>>>> there are
>>>>>> no regressions (and very few known failures). My inflation stress 
>>>>>> testing
>>>>>> is still in process. I had to restart that testing after a 
>>>>>> thunderstorm
>>>>>> related power failure took down my servers in Florida. Sigh...
>>>>>>
>>>>>> Thanks, in advance, for any comments, questions, or suggestions.
>>>>>>
>>>>>> Dan
>>>>>
>>
>