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From Jeremiah Jordan <>
Subject Re: memory estimate for each key in the key cache
Date Mon, 19 Dec 2011 22:15:35 GMT
It is not telling you to multiply your key size by 10-12, it is telling you to multiply the
output of the nodetool cfstats reported "key cache size" by 10-12.


On Dec 18, 2011, at 6:37 PM, Guy Incognito wrote:

> to be blunt, this doesn't sound right to me, unless it's doing something rather more
clever to manage the memory.
> i mocked up a simple class containing a byte[], ByteBuffer and long, and the shallow
size alone is 32 bytes.  deep size with a byte[16], 1-byte bytebuffer and long is 132.  this
is a on a 64-bit jvm on win x64, but is consistent(ish) with what i've seen in the past on
linux jvms.  the actual code has rather more objects than this (it's a map, it has a pair,
decoratedKey) so would be quite a bit bigger per key.
> On 17/12/2011 03:42, Brandon Williams wrote:
>> On Fri, Dec 16, 2011 at 9:31 PM, Dave Brosius<>  wrote:
>>> Wow, Java is a lot better than I thought if it can perform that kind of
>>> magic.  I'm guessing the wiki information is just old and out of date. It's
>>> probably more like 60 + sizeof(key)
>> With jamm and MAT it's fairly easy to test.  The number is accurate
>> last I checked.
>> -Brandon

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