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From Narendra Sharma <>
Subject Re: ParNew (promotion failed)
Date Wed, 23 Mar 2011 18:27:21 GMT
I understand that. The overhead could be as high as 10x of memtable data
size. So overall the overhead for 16CF collectively in your case could be
300*10 = 3G.


On Wed, Mar 23, 2011 at 11:18 AM, ruslan usifov <>wrote:

> 2011/3/23 Narendra Sharma <>
>> I think it is due to fragmentation in old gen, due to which survivor area
>> cannot be moved to old gen. 300MB data size of memtable looks high for 3G
>> heap. I learned that in memory overhead of memtable can be as high as 10x of
>> memtable data size in memory. So either increase the heap or reduce the
>> memtable thresholds further so that old gen gets freed up faster. With
>> 16CFs, I would do both i.e. increase the heap to say 4GB and reduce memtable
>> thresholds further.
>> I think that you don't undestend me, 300MB is a summary thresholds on all
> 16 CF, so one memtable_threshold is about 18MB. Or all the same it is
> necessary to reduce memtable_threshold?

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