RFR (XS): 8053998: Hot card cache flush chunk size too coarse grained

Mikael Gerdin mikael.gerdin at oracle.com
Wed Aug 20 13:51:16 UTC 2014


Hi,

On 2014-08-20 15:42, Marcus Larsson wrote:
> Hello,
>
> On 08/18/2014 04:50 PM, Mikael Gerdin wrote:
>> Hi Marcus,
>>
>> On 2014-08-18 09:27, Marcus Larsson wrote:
>>> Hi,
>>>
>>> Can I have reviews for this small patch changing the hot card cache
>>> flush chunks to a fixed size?
>>>
>>> CR:
>>> http://cr.openjdk.java.net/~mgerdin/mlarsson/webrev-8053998/
>>
>> Can you move the value "32" to a constant? Both stringTable.cpp and
>> symbolTable.cpp define a
>> const int ClaimChunkSize = 32;
>> That seems like a reasonable pattern, but you should probably make it
>> a static global or scope it inside G1HotCardCache.
>
> Made it a static constant in G1HotCardCache.
>
> New webrev:
> http://cr.openjdk.java.net/~mgerdin/mlarsson/webrev-8053998v2/

Looks good.

/Mikael

>
>>
>> Otherwise it looks good.
>>
>> For the record I asked Marcus about the value "32" and he had done
>> some experiments to come up with the number.
>
> Yes, I should have mentioned this in my first email.
> I measured with some different fixed sizes, and also by
> over-partitioning the cache to 10 chunks per active worker thread.
> The smaller the chunk size the better results I got, so 32 seemed like a
> good number without making it too small.
>
>>
>> /Mikael
>>
>>>
>>> Bug:
>>> https://bugs.openjdk.java.net/browse/JDK-8053998
>>>
>>> Testing:
>>> jprt, SPECjbb2013
>>>
>>> Thanks,
>>> Marcus
>
> Thanks,
> Marcus


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