RFR(S): 8134889: Kitchensink stress test crashes with out of memory error

[Derek White]

Hi Mikael,

I promised a webrev, but got buried by gatekeeping for a few days.

WEBREV: http://cr.openjdk.java.net/~drwhite/8134889/webrev.02/

Incremental:
http://cr.openjdk.java.net/~drwhite/8134889/webrev01.v.02/

Thanks!

  - Derek

On 4/26/16 6:37 PM, Derek White wrote:
> Hi Mikael,
>
> On 4/21/16 10:36 AM, Derek White wrote:
>> Hi Mikael,
>>
>> On 4/21/16 4:02 AM, Mikael Gerdin wrote:
>>> Hi Derek,
>>>
>>> On 2016-04-20 23:48, Derek White wrote:
>>>> Still looking for reviews for a small fix for a P2 bug...
>>>>
>>>> Thanks!
>>>>
>>>> On 4/7/16 6:07 PM, Derek White wrote:
>>>>> Summary:
>>>>> The remaining part of this bug deals with running out of address 
>>>>> space
>>>>> on 32-bit JVMs running on Win64. This fix is simply to have a hard
>>>>> limit on GC threads (still larger than necessary) on 32-bit JVMs. The
>>>>> new limit is 16 (2 * switch_pt).
>>>>>
>>>>> Note that this overlaps somewhat with several "# of GC thread" bugs
>>>>> including:
>>>>>  - 8131932 <https://bugs.openjdk.java.net/browse/JDK-8131932> :
>>>>> Ergonomics oversize number of GC threads for small JVMs on large 
>>>>> systems
>>>>>  - 8153225 <https://bugs.openjdk.java.net/browse/JDK-8153225>: G1
>>>>> creates too many concurrent refinement threads by default
>>>>>  - 7189147 <https://bugs.openjdk.java.net/browse/JDK-7189147>: GC
>>>>> threads should be created as needed not all at once
>>>>>
>>>>> Doing the correct thing in general will require a lot more 
>>>>> performance
>>>>> analysis. The fix here is simple, only affects 32-bit JVMs running on
>>>>> >= 24 core machines, and will reduce OOM crashes in nightly testing.
>>>>>
>>>>> BUG: 8134889 <https://bugs.openjdk.java.net/browse/JDK-8134889>
>>>>> WEBREV: http://cr.openjdk.java.net/~drwhite/8134889/webrev.01/
>>>
>>> Fix looks good.
>>> I wonder about the cast to unsigned int, though.
>>> It seems weird that it's needed since all the other operands are 
>>> unsigned ints in the calculation.
>>
>> Yes, that does look weird. I can't recall why I added it either.
>>
>>      unsigned int switch_pt = bar;
>>      unsigned int threads = foo;
>>      threads = MIN2(threads, 2*switch_pt)
>>
>> Wait a minute, according to the interweb, the type of the literal '2' 
>> is "int" (eg. signed). I think one compiler complained on a jprt run. 
>> Doing a jprt run without the cast...
> So jprt is happy with or with the cast. I had the type promotion rules 
> wrong in my head.
> signed * unsigned = unsigned.
>
> I'll remove the cast and update the webrev.
>
> Thanks,
>
>   - Derek

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