Review request: 8024638: Count and expose the amount of committed memory in the metaspaces

[Stefan Karlsson]

On 09/12/2013 10:11 AM, Bengt Rutisson wrote:
>
> Stefan,
>
> Looks good.

Thanks, Bengt.

StefanK

>
> For the record, Stefan and I talked about introducing some 
> verification code to check that the reserved and committed sizes that 
> the VirtualSpaceList keeps track of is the same as the sum of the 
> corresponding values for all nodes. We agreed to add that as a 
> separate change.
>
> Thanks,
> Bengt
>
> On 9/11/13 11:03 PM, Stefan Karlsson wrote:
>> http://cr.openjdk.java.net/~stefank/8024547/webrev.01/
>>
>> Further testing showed that one of the asserts in 
>> actual_committed_size was incorrect when the the middle region of the 
>> VirtualSpace was empty and the middle alignment was larger than the 
>> other alignments. This can happen when large pages are used and the 
>> size of the VirtualSpace is within the range [large_page_size, 2 * 
>> large_page_size).
>>
>> I rewrote the asserts to handle that and similar cases. I also added 
>> new unit test cases that provoked this incorrect assert.
>>
>> Thanks Erik Helin for finding this (and also for helping out with the 
>> original patch).
>>
>> thanks,
>> StefanK
>>
>> On 9/11/13 6:10 PM, Stefan Karlsson wrote:
>>> http://cr.openjdk.java.net/~stefank/8024547/webrev.00/
>>>
>>> This change adds code to track the committed memory in the metaspaces.
>>>
>>> This fix is a prerequisite for:
>>>   8024547: MaxMetaspaceSize should limit the committed memory used 
>>> by the metaspaces
>>>
>>> The patch is built upon this change, which is also out for review:
>>> http://mail.openjdk.java.net/pipermail/hotspot-dev/2013-September/010766.html 
>>>
>>>
>>> Changes in the patch:
>>>
>>> - Renamed VirtualSpaceList::_virtual_space_total to 
>>> VirtualSpaceList::_reserved_words.
>>>
>>> - Introduced a VirtualSpaceList::_committed_words.
>>>
>>> - Added a new function VirtualSpace::actual_committed_size(), which 
>>> reports the memory committed by the OS. The per-existing function 
>>> VirtualSpace::committed_size() only reports the amount of memory 
>>> asked for by calls to VirtualSpace::expand_by, which can be 
>>> significantly less because of OS allocation granularities and large 
>>> pages.
>>>
>>> - Added code to tracks when the VirtualSpaces in the 
>>> VirtualSpaceNodes are created, deleted, and expanded.
>>>
>>> - Added unit tests.
>>>
>>> thanks,
>>> StefanK
>>
>