RFR (S) 8008217: CDS: Class data sharing limits the malloc heap on Solaris

[Coleen Phillimore]

On 3/18/2013 1:32 PM, Vladimir Kozlov wrote:
> Coleen,
>
> First, your description is not accurate. Should be something like this:
>
> "In 64bit VM move CDS archive address to 32G on all platforms using 
> new flag SharedBaseAddress.
> In 32bit VM set CDS archive address to 2Gb on Linux and let other OSs 
> pick the address."

Yes, that sounds better than what I wrote.

>
> I think you need to always set SharedBaseAddress to 32G with the flag 
> description that it is default for 64-bit VM. Special flag setting for 
> Linux in 32bit VM could be done in VirtualSpaceNode() or in 
> arguments.cpp (where CDS values are set) under #ifdef if the value is 
> default.

I don't understand this comment.   Does it mean make it 32G and 2G in 
globals.hpp rather than in the globals_os_cpu.hpp files?  I don't have 
good experiences with special case code in arguments.cpp and the 
complexity we keep adding to it, and want to avoid that.

>
> Also setting in 32bit VM the CDS address on Linux to 2G may limit 
> ability to specify large java heap size since 2G is in the middle of 
> virtual space. Can it be somewhere at the top of virtual space (4G - 
> cds_size)? Or at the bottom? Did you look on heap mapping in that 
> case? Note, HeapBaseMinAddress was never used in 32bit VM before NPG.
>

I was wondering what a better address than 2G would be for Linux. Which 
is why I put the settings in the different os_cpu files.  If I let Linux 
default, it picks a high address for -Xshare:dump but then cannot get 
this higher address when ute tests are run.   2G is sort of in the 
middle which always seems to work, and with 32 bit, the Java heap 
shouldn't be that large anyway because otherwise people would be using 
64 bits.   Maybe 3G might be better, or 3.5G.
I didn't dare try to use lower addresses because some other application 
specific data would be more likely to want these addresses.   So, that's 
another reason I made it an option and split their settings out.

Thanks,
Coleen

> Thanks,
> Vladimir
>
> On 3/18/13 7:51 AM, Coleen Phillimore wrote:
>>
>> Adding in some more potential reviewers...  please review!
>> Thanks,
>> Coleen
>>
>> On 03/15/2013 02:25 PM, Coleen Phillimore wrote:
>>> Summary: Don't use HeapBaseMinAddress on solaris, let the OS pick the
>>> CDS archive address on solaris.  Move all CDS archive addresses up to
>>> 32G on 64 bit.
>>>
>>> On Linux, this still uses 2*G address because running ute, we can't
>>> seem get the same address that -Xshare:dump choses. Solaris chooses a
>>> higher address which seems to work fine.
>>>
>>> open webrev at http://cr.openjdk.java.net/~coleenp/8008217/
>>> bug link at http://bugs.sun.com/view_bug.do?bug_id=8008217
>>>
>>> Tested manually with gc/gctests/ManyObjects on all platforms. To add
>>> a jtreg test, we'd have to introduce a new flag to change the location
>>> of the shared archive because we don't have write access to JAVA_HOME
>>> while testing.   Do people think this is worth doing?
>>>
>>> Thanks,
>>> Coleen
>>