RFR(S) JDK-8025526: VirtualSpace should support per-instance disabling of large pages

[Stefan Karlsson]

On 2013-10-02 12:23, Erik Helin wrote:
> On 2013-09-30, Mikael Gerdin wrote:
>> Erik,
>>
>> On 09/27/2013 05:10 PM, Erik Helin wrote:
>>> Hi Mikael,
>>>
>>> what do you think about splitting the VirtualSpace::initialize method
>>> into two methods:
>>> - VirtualSpace::initialize
>>> - VirtualSpace::initialize_with_granularity
>>>
>>> Then initialize would just call initialize_with_granularity like the
>>> following:
>>>
>>>    bool VirtualSpace::initialize(ReservedSpace rs, size_t committed_size) {
>>>      size_t granularity = os::page_size_for_regions(rs.size(), rs.size(), 1);
>>>      return initialize_with_granularity(rs, committed_size, granularity);
>>>    }
>>>
>>>    bool VirtualSpace::initialize_with_granularity(ReservedSpace rs,
>>>      size_t committed_size, size_t granularity) {
>>>      assert(granularity > 0, "Can't have 0 as granularity");
>>>      // old initialize code
>>>      _middle_alignment = granularity;
>>>      // rest of old initialized code
>>>    }
>>>
>>> This way, we get rid of the default argument and don't have to check if
>>> max_commit_granularity == 0.
>> I like your suggestion.
>> I've uploaded a second webrev which implements your suggestion.
>> I had to update the test code so I re-ran the tests on all platforms.
>>
>> New webrev: http://cr.openjdk.java.net/~mgerdin/8025526/webrev.1/
> Besides from Thomas' comment about the default value for the method
> parameter, this looks good! Thanks for also adding tests!

Yes. Looks good.

thanks,
StefanK

>
> Erik
>
>> /Mikael
>>
>>> Thanks,
>>> Erik
>>>
>>> On 2013-09-27, Mikael Gerdin wrote:
>>>> Hi,
>>>>
>>>> As part of ongoing work in getting Metaspace to properly enforce the
>>>> MaxMetaspaceSize limit [JDK-8024547] we need to extend the
>>>> VirtualSpace class to allow us to set the granularity at which
>>>> VirtualSpace commits pages from the OS.
>>>>
>>>> Summary of changes:
>>>> Extend VirtualSpace::initialize to take a parameter for setting the
>>>> maximum commit granularity. The default value 0 keeps the previous
>>>> behavior of using os::page_size_for_region to determine the
>>>> granularity.
>>>> Add unit tests for disabling and enabling large pages both at the
>>>> ReservedSpace and the VirtualSpace level.
>>>>
>>>> Testing:
>>>> JPRT run (includes running the new tests)
>>>>
>>>> Webrev: http://cr.openjdk.java.net/~mgerdin/8025526/webrev.0
>>>> Bug link: https://bugs.openjdk.java.net/browse/JDK-8025526
>>>>
>>>> /Mikael