RFR 8220238 : Enhancing j.l.Runtime/System::gc specification with an explicit 'no guarantee' statement

[Mandy Chung]

On 5/30/19 8:55 AM, Peter Levart wrote:
> Yes Roger, this sounds better to me.
>
> Maybe even easier:
>
> "There is no guarantee that this effort will recycle any particular 
> number of unused objects, reclaim any particular amount of space, or 
> complete before the method returns (or ever)."
>

+1 and take out "(or ever)"

I agree that this is simpler and clear that there is no guarantee of GC 
completion when this method returns.

Mandy

> So, hypothetically, the effort triggered by System.gc() may never 
> complete although the method will eventually return. Is this what was 
> meant to be said?
>
> Is it necessary to have this (or ever) at the end? What's the purpose 
> of it? If the method returns before the attempt completes, there's no 
> way to track the attempt to its completion and doesn't matter if it 
> eventually completes or not. The completion is already out of bounds 
> for this method when it says: "there is not guarantee that the attempt 
> completes before the method returns"...
>
> Regards, Peter
>
> On 5/30/19 4:42 PM, Roger Riggs wrote:
>> Hi,
>>
>> Though I see your point about gc() eventually returns, the spec 
>> typically does not
>> guarantee than any method eventually returns.  That's more a quality 
>> of service attribute.
>> The sentence refers to the effort to reclaim space, not the method call.
>>
>> Would it clarify the case to add a qualification to the end of the 
>> sentence:
>> " before the method returns or ever."
>>
>> As a whole:
>>
>>      * Runs the garbage collector in the Java Virtual Machine.
>>      * <p>
>>      * Calling this method suggests that the Java Virtual Machine
>>      * expend effort toward recycling unused objects in order to
>>      * make the memory they currently occupy available for reuse
>>      * by the Java Virtual Machine.
>>      * When control returns from the method call, the Java Virtual 
>> Machine
>>      * has made a best effort to reclaim space from all unused objects.
>>      * There is no guarantee that this effort will recycle any 
>> particular
>>      * number of unused objects, reclaim any particular amount of space,
>>      * or complete at any particular time, if at all <b>before the 
>> method returns or ever</b>.
>>
>> Thanks, Roger
>>
>> On 05/30/2019 06:27 AM, Roman Kennke wrote:
>>>>> Any other comments on:
>>>>> "* Runs the garbage collector in the Java Virtual Machine.
>>>>> * <p>
>>>>> * Calling this method suggests that the Java Virtual Machine
>>>>> * expend effort toward recycling unused objects in order to
>>>>> * make the memory they currently occupy available for reuse
>>>>> * by the Java Virtual Machine.
>>>> The following two statements...
>>>>
>>>> 1st:
>>>>> * When control returns from the method call, the Java Virtual Machine
>>>>> * has made a best effort to reclaim space from all discarded objects.
>>>> 2nd:
>>>>> * There is no guarantee that this effort will recycle any particular
>>>>> * number of unused objects, reclaim any particular amount of space,
>>>>> * *or complete* at any particular time, if *at all*.
>>>>> "
>>>> ...makes one think that it is OK (by the spec) for System.gc() to 
>>>> never
>>>> complete.
>>>>
>>>> Could it rather be specified that System.gc() eventually completes?
>>>>
>>> +1 I was thinking the same.
>>>
>>> I think the intention is that GC may never actually complete, but
>>> System.gc() must be guaranteed to eventually return.
>>>
>>> Roman
>>>
>>
>