RFR (xs): 8134992: vm/gc/compact/Compact_InternedStrings_Strings failed due to a malloc() failure

Derek White derek.white at oracle.com
Tue Feb 23 15:18:57 UTC 2016


Thanks Mikael!

On 2/23/16 4:15 AM, Mikael Gerdin wrote:
> Hi Derek,
>
>
> On 2016-02-22 19:39, Derek White wrote:
>> Very simple fix for a bug on Solaris and small performance issue 
>> everywhere else.
>>
>> *Bug*: JDK-8134992 <https://bugs.openjdk.java.net/browse/JDK-8134992> 
>> vm/gc/compact/Compact_InternedStrings_Strings failed due to a 
>> malloc() failure
>> *Webrev*: http://cr.openjdk.java.net/~drwhite/8134992/webrev.01
>
> Good catch!
>
> The change looks good to me.
>
> /Mikael
>
>> *Tests*: jprt, partial Aurora perf.
>>
>> *Background*:
>> Many of the vm.gc.compact tests create large strings and/or char 
>> arrays that don't get allocated in the young gen. 
>> RuntimeStub::_new_array_Java() and 
>> RuntimeStub::_new_array_nozero_Java() have to call 
>> CollectedHeap::new_store_pre_barrier() when deferred store barriers 
>> are turned on. Unless the object is in the young gen, 
>> new_store_pre_barrier() marks every card for the entire new object as 
>> dirty. If the object is very large, this can result in so many 
>> enqueued dirty cards that it runs out of memory (due to the malloc 
>> constraints in Solaris).
>>
>> But primitive arrays don't have any references that need need a store 
>> barrier, so the whole issue can be avoided in this case. Doing so 
>> reduces gc's malloc space usage by up to 30% in these compact tests.
>>
>> Note that these tests are essentially String.intern micro-benchmarks, 
>> so I haven't seen a performance improvement in more general code.
>>
>> Thanks!
>>  - Derek White
>>
>>
>> 	
>> 	*clean:* 	*8134992* 	
>> 	
>> *KB* 	*
>> * 	*reserved* 	*reserved* 	*diff* 	*%*
>> Humongous_InternedStrings 	malloc 	63743 	48669 	-15,074 	24%
>> Compact_InternedStrings1 	malloc 	41738 	39328 	-2,410 	6%
>> Compact_Arrays 	malloc 	50943 	50940 	-3 	0%
>> Humongous_Strings 	malloc 	66503 	50989 	-15,514 	23%
>> *Compact_Strings* 	malloc 	*62757* 	50941 	-11,816 	19%
>> /Compact_Strings_InternedStrings/ 	malloc 	68024 	50944 	-17,080 	25%
>> Humongous_NonbranchyTree5M 	malloc 	51020 	51038 	18 	
>> Compact_InternedStrings 	malloc 	62828 	50938 	-11,890 	19%
>> Compact_NonbranchyTree 	malloc 	51024 	51016 	-8 	0%
>> Compact_Arrays1 	malloc 	50673 	50682 	9 	0%
>> Humongous_Arrays 	malloc 	50949 	50943 	-6 	0%
>> Compact_NonbranchyTree1 	malloc 	50704 	50718 	14 	0%
>> Compact_NonbranchyTree_TwoFields 	malloc 	51042 	51015 	-27 	0%
>> Compact_Strings1 	malloc 	52072 	50681 	-1,391 	3%
>> Compact_Arrays_ArrayOf1 	malloc 	50692 	50689 	-3 	0%
>> Humongous_Strings1 	malloc 	52003 	50709 	-1,294 	2%
>> Compact_Strings_ArrayOf1 	malloc 	52081 	47632 	-4,449 	9%
>> Compact_InternedStrings_NonbranchyTree 	malloc 	64031 	50980 
>> -13,051 	20%
>> Humongous_InternedStrings1 	malloc 	43035 	40631 	-2,404 	6%
>> Compact_TwoFields_InternedStrings 	malloc 	50953 	50938 	-15 	0%
>> Compact_NonbranchyTree_TwoFields1 	malloc 	50708 	50699 	-9 	0%
>> Compact_NonbranchyTree_ArrayOf 	malloc 	51013 	51008 	-5 	0%
>> Humongous_Arrays5M 	malloc 	50949 	50955 	6 	0%
>> Compact_Arrays_TwoFields 	malloc 	50941 	50955 	14 	0%
>> Compact_Arrays_ArrayOf 	malloc 	50945 	50949 	4 	0%
>> Humongous_NonbranchyTree1 	malloc 	50709 	50738 	29 	0%
>> Compact_Arrays_TwoFields1 	malloc 	50694 	50710 	16 	0%
>> Humongous_NonbranchyTree 	malloc 	51018 	51041 	23 	0%
>> Compact_NonbranchyTree_ArrayOf1 	malloc 	50728 	50711 	-17 	0%
>> Humongous_Arrays1 	malloc 	50694 	50699 	5 	0%
>> Compact_InternedStrings_Strings 	malloc 	63836 	50865 	-12,971 	20%
>> Compact_Strings_TwoFields 	malloc 	72703 	50932 	-21,771 	30%
>> Compact_Strings_ArrayOf 	malloc 	66452 	50932 	-15,520 	23%
>> *AVG DIFF (KB)* 	
>> 	
>> 	
>> 	*-4,442* 	*7.15%*
>>
>>
>

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