浅谈innodb_buffer_pool_size的设置
设置innodb_buffer_pool_size为可用内存的50-60%.注意可用内存应该是linux命令free下的-/+ buffers/cache行的free值；innodb_buffer_pool_size的值应该是在mysql实例没有启动情况下的值，而不是实例启动后的值。见示例。
示例：
（1）在没有对innodb_buffer_pool_size参数优化前：
SELECT sql_no_cache
N1.N_NAME AS SUPP_NATION,
N2.N_NAME AS CUST_NATION,
EXTRACT(YEAR FROM L_SHIPDATE) AS L_YEAR,
SUM(L_EXTENDEDPRICE * (1 - L_DISCOUNT)) AS REVENUE
FROM SUPPLIER,
LINEITEM,
ORDERS,
CUSTOMER,
NATION N1,
NATION N2
WHERE
S_SUPPKEY = L_SUPPKEY
AND O_ORDERKEY = L_ORDERKEY
AND C_CUSTKEY = O_CUSTKEY
AND S_NATIONKEY = N1.N_NATIONKEY
AND C_NATIONKEY = N2.N_NATIONKEY
AND (N1.N_NAME = 'FRANCE' AND N2.N_NAME = 'GERMANY' OR N1.N_NAME = 'GERMANY' AND N2.N_NAME = 'FRANCE')
AND L_SHIPDATE >= DATE '1995-01-01'
AND L_SHIPDATE <= DATE '1996-12-31'
GROUP BY
SUPP_NATION,
CUST_NATION,
L_YEAR
ORDER BY
SUPP_NATION,
CUST_NATION,
L_YEAR;
+-------------+-------------+--------+--------------------+
| SUPP_NATION | CUST_NATION | L_YEAR | REVENUE |
+-------------+-------------+--------+--------------------+
| FRANCE | GERMANY | 1995 | 54639732.7336 |
| FRANCE | GERMANY | 1996 | 54633083.30760003 |
| GERMANY | FRANCE | 1995 | 52531746.66970005 |
| GERMANY | FRANCE | 1996 | 52520549.022399954 |
+-------------+-------------+--------+--------------------+
4 rows in set (2 min 0.90 sec)
查询耗费2 min 0.90 sec
（2）数据库实例启动情况下对可用内存的调整
[root@gflinux ~]# free
total used free shared buffers cached
Mem: 1034708 999860 34848 0 2852 161448
-/+ buffers/cache: 835560 199148
Swap: 4192924 152 4192772
设置innodb_buffer_pool_size值为可用内存的60%
199148*60%=119M，取128M
重启数据库后再次运行上述查询语句，查看执行时间：
+-------------+-------------+--------+--------------------+
| SUPP_NATION | CUST_NATION | L_YEAR | REVENUE |
+-------------+-------------+--------+--------------------+
| FRANCE | GERMANY | 1995 | 54639732.7336 |
| FRANCE | GERMANY | 1996 | 54633083.30760003 |
| GERMANY | FRANCE | 1995 | 52531746.66970005 |
| GERMANY | FRANCE | 1996 | 52520549.022399954 |
+-------------+-------------+--------+--------------------+
4 rows in set (7.55 sec)
（3）数据库实例没有启动情况下对可用内存的调整
[root@gflinux ~]# service mysql stop
Shutting down MySQL.... [ OK ]
[root@gflinux ~]# free
total used free shared buffers cached
Mem: 1034708 430908 603800 0 4396 353292
-/+ buffers/cache: 73220 961488
Swap: 4192924 152 4192772
设置innodb_buffer_pool_size值为可用内存的60%
961488*60%=577M，取580M
重启数据库后再次运行上述查询语句，查看执行时间：
+-------------+-------------+--------+--------------------+
| SUPP_NATION | CUST_NATION | L_YEAR | REVENUE |
+-------------+-------------+--------+--------------------+
| FRANCE | GERMANY | 1995 | 54639732.7336 |
| FRANCE | GERMANY | 1996 | 54633083.30760003 |
| GERMANY | FRANCE | 1995 | 52531746.66970005 |
| GERMANY | FRANCE | 1996 | 52520549.022399954 |
+-------------+-------------+--------+--------------------+
4 rows in set (1.90 sec)
查询时间缩短为2s左右。