How much memory do I need for innodb buffer pool? I read here that 


  You need buffer pool a bit (say 10%) larger than your data (total size
  of Innodb TableSpaces)


On the other hand I've read elswher that innodb_buffer_pool_size must be up to %80 of the memory. So I'm really confused how should I choose the best size for the pool. My database size is about 6GB and my total memory 64GB. Also I'm wondering if I increase the buffer pool size, I should shrink the number of maximum connections to make room for extra buffer, or these parameters are independent. Thanks
If you go strictly by that rule of accommodating an addition 10%, here is my suggestion:

SELECT CONCAT(CEILING(RIBPS/POWER(1024,pw)),SUBSTR(' KMGT',pw+1,1))
Recommended_InnoDB_Buffer_Pool_Size FROM
(
    SELECT RIBPS,FLOOR(LOG(RIBPS)/LOG(1024)) pw
    FROM
    (
        SELECT SUM(data_length+index_length)*1.1*growth RIBPS
        FROM information_schema.tables AAA,
        (SELECT 1 growth) BBB
        WHERE ENGINE='InnoDB'
    ) AA
) A;


This will produce exactly what you need to set innodb_buffer_pool_size in /etc/my.cnf. If you want to account for 25% increase in data and indexes over time, please change (SELECT 1 growth) BBB to (SELECT 1.25 growth) BBB

Recently, I answered another question like this in the DBA StackExchange.