Following shows how the size of memtable is updated:
currentThroughput.addAndGet(cf.size());
The jconsole/JMX shows this and this doesn't account for the overhead of
holding the data in in-memory data structures.
The size of CF, SuperColumn and Column is calculated as following:
Column Size:
public int size()
{
/*
* Size of a column is =
* size of a name (short + length of the string)
* + 1 byte to indicate if the column has been deleted
* + 8 bytes for timestamp
* + 4 bytes which basically indicates the size of the byte array
* + entire byte array.
*/
return DBConstants.shortSize_ + name.remaining() +
DBConstants.boolSize_ + DBConstants.tsSize_ + DBConstants.intSize_ +
value.remaining();
}
SuperColumn Size:
public int size()
{
int size = 0;
for (IColumn subColumn : getSubColumns())
{
size += subColumn.serializedSize();
}
return size;
}
ColumnFamily Size:
int size()
{
int size = 0;
for (IColumn column : columns.values())
{
size += column.size();
}
return size;
}
Hope this makes it clear.
Thanks,
Naren
On Mon, Mar 28, 2011 at 2:15 PM, ruslan usifov <ruslan.usi...@gmail.com>wrote:
>
>
> 2011/3/29 Narendra Sharma <narendra.sha...@gmail.com>
>
>> This is because the memtable threshold is not correct to the last byte.
>> The threshold basically account for column name, value and timestamp (or the
>> serialized column). It doesn't account for all the in-memory overhead for
>> maintaining the data and references etc.
>>
>>
> Overhead in 2 times???? Hm why so many. Also in JMX (throw jconsole) i
> don't see any overhead, when memtable reach it memory threshold it will be
> reset to very low value (about 300 - 400 KB)
>
--
Narendra Sharma
Solution Architect
*http://www.persistentsys.com*
*http://narendrasharma.blogspot.com/*
