RFR: 8000617: It should be possible to allocate memory without the VM dying.

[Keith McGuigan]

May as well lift the allocation fail strategy up into Thread::allocate() as well, replacing the boolean parameter there.

I think you're replacements of new(std::nothrow) XXX() wit new (EXIT_OOM) XXX() are all reversed: if it was nothrow you want to replace it with RETURN_NULL.

--
- Keith

On Oct 12, 2012, at 9:14 AM, Nils Loodin wrote:

> 
> Hey guys!
> 
> Thanks for yet another round of informative code reviews!
> So I got rid of all the instances of std::nothrow throughout the code and replaced them with a new shiny and descriptive enum.
> 
> Was able to fold together a few specialized operator new() because of it, with more shared code as a result.
> 
> What do you think now?
> http://cr.openjdk.java.net/~nloodin/8000617/webrev.04/
> 
> Have a nice weekend!
> 
> Regards,
> Nils Loodin
> 
> 
> On 10/12/2012 06:47 AM, David Holmes wrote:
>> On 12/10/2012 2:21 PM, David Holmes wrote:
>>> Hi Nils,
>>> 
>>> There are a number of existing bugs/RFEs in this area - not sure we
>>> needed yet another.
>>> 
>>> On 11/10/2012 10:55 PM, Nils Loodin wrote:
>>>> Hey guys.
>>>> 
>>>> Your comments on this issue are great! So here's another version that
>>>> uses an enum instead of std::nothrow_t trickery!
>>>> 
>>>> http://cr.openjdk.java.net/~nloodin/8000617/webrev.03/
>>> 
>>> I dislike the std::nothrow usage that NMT introduced (there aren't even
>> 
>> Apologies it wasn't NMT that introduced this - it is a bit older than
>> that: April 2011. See
>> https://jbs.oracle.com/bugs/browse/JDK-7036747
>> 
>> and some comments in
>> 
>> https://jbs.oracle.com/bugs/browse/JDK-4719004
>> 
>> Till then we had avoided any use of C++ std:: stuff - particularly
>> anything related to the exception mechanism, which we don't use at all.
>> 
>>> any exceptions involved!) but introducing a completely different
>>> mechanism seems counter-productive. I prefer the "alloc fail strategy"
>>> approach but would like to see this solved holistically, replacing
>>> std::nothrow. Given there exist bigger RFE's to have the VM handle all
>>> OOM situations gracefully rather than just aborting, I'd rather not see
>>> just another point-patch put in place.
>> 
>> The bigger problem is probably still too big to really handle - so
>> either copy what we already introduced for CHeapObj to ResourceObj for
>> consistency, or replace both with something better.
>> 
>> Cheers,
>> David
>> -----
>> 
>>> For the record I found the original proposal extremely confusing:
>>> nothrow_constant vs throw_constant.
>>> 
>>> Sorry.
>>> 
>>> David
>>> -----
>>> 
>>>> Regards,
>>>> Nils Loodin
>>>> 
>>>> 
>>>> 
>>>> 
>>>> On 10/11/2012 01:21 PM, Dmitry Samersoff wrote:
>>>>> Keith,
>>>>> 
>>>>> Personally, I would prefer explicit AllocWithoutThrow(...) function.
>>>>> 
>>>>> -Dmitry
>>>>> 
>>>>> 
>>>>> 
>>>>> On 2012-10-11 03:40, Keith McGuigan wrote:
>>>>>> 
>>>>>> Personally, I don't have strong feelings on how this is implemented,
>>>>>> other than it should be done in a way that's maintainable going
>>>>>> forward
>>>>>> and easily understandable by future generations of hotspot developers.
>>>>>> With this in mind, the only potential solution that I don't like is
>>>>>> using a boolean with naked true/false values as discriminators.
>>>>>> 
>>>>>> Using some sort of "failure mode" parameter is the natural way to do
>>>>>> this, whether it be enums, std::nothrow_t, or whatever. Since
>>>>>> std::nothrow_t already has a type and one value, and is already
>>>>>> present
>>>>>> in the few places we're interested in, it seemed easy to simple just
>>>>>> add
>>>>>> a new value to use. However if this ends up being confusing because
>>>>>> this is not the normal use of std::notype_t, then fine, we can do
>>>>>> something else.
>>>>>> 
>>>>>> --
>>>>>> - Keith
>>>>> 
>>>>> 
>>>> 
>