For your reference i am trying to explain some concepts also.
Key hit rate
There are basically two forms of key hit rate
1.Key Read Efficiency
Key Reads: The number of physical reads of a key block from disk.
Key Read Request: The number of requests to read a key block from the
Key Read Efficiency = [1 - (Key_reads/Key_read_requests)]*100
Key Read Efficiency: The ratio of the number of physical reads of a
key block from the cache to the number of requests to read a key block
from the cache in percentage. The MySQL performance is good if the
value of Key Read Efficiency is 90 percent and above. Increasing the
size of the cache improves the value of Key Read Efficiency and hence
an improved the performance.
2.Key Write Efficiency
Key Writes: The number of physical writes of a key block to disk.
Key Write Request: The number of requests to write a key block to the
Key Write Efficiency=(Key_write/Key_write_requests)*100
Key Write Efficiency: The ratio of the number of physical writes of a
key block to the cache to the number of requests to write a key block
to the cache in percentage. For a good performance of the MySQL
server, the value of Key Write Efficiency must be 90 percent and
above. If it is found less, then you can increase the size of the
cache to improve the performance.
Key Buffer Used
Find value of key_buffer_size as
show variables like 'key_buffer_size';
convert it into MB.
Find the All MyISAM index Size :
SELECT SUM(INDEX_LENGTH)/(1024*1024) 'Index Size' FROM
information_schema.TABLES where ENGINE='MyISAM' AND TABLE_SCHEMA NOT
(Index Size)/key_buffer_size(in MB) * 100
if result is (<=100 ) then your all indexes are cached into key_buffer
if result is (>100) then your all indexes are not cached into
key_buffer you may gain performance boost by increasing
query cache hitrate
Hit rate = Qcache_hits / (Qcache_hits + Com_select) * 100
Insert rate = Qcache_inserts / (Qcache_hits + Com_select) * 100
Prune rate = (Qcache_lowmem_prunes / Qcache_inserts) * 100