Request for Review (s) - 8157620: Guarantee in run_task(task, num_workers) fails

[Jon Masamitsu]

Derek,

Thanks for the review.

On 6/7/2016 1:43 PM, Derek White wrote:
> Hi Jon,
>
> The new code looks good!
>
> While reviewing this I looked over WorkerManager again, and saw a 
> problem in the error handling:
>
>  - Line 60 checks for errors creating the WorkerThread or OS thread.
>  - Line 66-67 unconditionally update created_workers and tries to 
> start a (possibly non-existent) thread.
>  - And I don't like the spacing of line 61, but that's a nit.
>
> I'm not sure if this should get fixed as a separate change or as part 
> of this one, but it looks bad.

Yes, that looks bad.  I'll fix it as part of a separate change.

Jon

>
> - Derek
>
> On 6/7/16 2:46 PM, Jon Masamitsu wrote:
>> New webrev and delta, respectively, with changes indicated below.
>>
>> http://cr.openjdk.java.net/~jmasa/8157620/webrev.01/
>>
>> http://cr.openjdk.java.net/~jmasa/8157620/webrev_delta.00_01/
>>
>> Jon
>>
>> On 6/7/2016 1:36 AM, Thomas Schatzl wrote:
>>> Hi Jon,
>>>
>>> On Fri, 2016-06-03 at 14:04 -0700, Jon Masamitsu wrote:
>>>> https://bugs.openjdk.java.net/browse/JDK-8157620
>>>>
>>>> A phase of a G1 collection chooses its own number of GC workers
>>>> but doesn't add more workers if more are needed than have been
>>>> created.   Add additional workers as needed.  Also changed the
>>>> guarantee to check the number of workers against the total number
>>>> of workers since the number of GC workers used to execute the
>>>> task may be different than active_workers (as in this case).
>>>>
>>>> Added an execution of TestGCOld with parameters that evoked the
>>>> failure.
>>>>
>>>> http://cr.openjdk.java.net/~jmasa/8157620/webrev.00/
>>>>
>>>> Tested fix with TestGCOld.
>>>> Stability tested with gc_test_suite
>>>>
>>>    looks good, with two comments:
>>>
>>> - I would _prefer_ if run_task(workgang, uint) always called
>>> add_workers() itself. Otherwise all of these invocations need to call
>>> add_workers() first themselves (if they do not limit themselves to
>>> active_workers).
>>>
>>> The run_task(workgang, uint) method has kind of been implemented as a
>>> short/quick way to run a workgang with a given number of threads, so
>>> this requirement adds additional boiler plate code again...
>>>
>>> - in the test, maybe put the -Xmx/-Xms right after the @run
>>> main/othervm like in the other tests just for consistency.
>>>
>>> ---------------------
>>>
>>> One comment related to the code changed, but unrelated to this CR: the
>>> code in G1ConcurrentMark::calc_parallel_marking_threads() looks
>>> (almost?) the same as AdaptiveSizePolicy::calc_active_conc_workers().
>>> Any arguments about cleaning this up at some point?
>>>
>>> When looking at the calculation of the
>>> AdaptiveSizePolicy::calc_default_active_workers() method, wouldn't it
>>> be better if instead of using Universe::heap()->capacity(), use
>>> something like Universe::heap()->used() (and actually e.g. for g1 one
>>> could subtract young gen and areas covered by primitive arrays too).
>>>
>>> Actually, this calculation should be different for young/old gen gc
>>> imho, as for both completely different areas are covered by the
>>> collection... (just some random thoughts when looking at this).
>>>
>>> Thanks,
>>>    Thomas
>>>
>>
>