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

[Peter Levart]

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)."

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
>>
>