http://blog.csdn.net/dba_waterbin/article/details/9669929
http://www.cnblogs.com/LMySQL/p/4689868.html
https://dev.mysql.com/doc/refman/5.7/en/large-page-support.html
http://www.cnblogs.com/ylqmf/archive/2012/11/23/2783717.html
http://www.cnblogs.com/cenalulu/p/4394695.html
http://www.linuxidc.com/Linux/2013-08/88227.htm
http://blog.chinaunix.net/uid-20785090-id-4065887.html
http://mogu.io/linux-hugepage-for-mysql-15
Hugepagesize 的话默认是每页 2MB。
[root@localhost ]# cat /proc/meminfo | grep -i huge HugePages_Total: 11 HugePages_Free: 11 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB //2MB
系统页一般大小:每页4K，
[root@localhost]# getconf PAGESIZE
4096
系统参数:
kernel.shmmax：表示单个共享内存段的最大值，以字节为单位,此值一般大于物理内存的一半.SHMMAX 的设置直接与SGA相关
kernel.shmmin:表示单个共享内存段的最小值,默认为1字节,通常不用设置
kernel.shmall：整个系统范围内可用共享页的总数,单位是页,在32位系统上1页等于4KB,也就是4096字节,
计算公式：shmmax/PAGE_SIZE
kernel.shmmin:整个系统范围内存段的最大数量,一般为4096个段
作用:
如果设置MySQL使用 huge page 至少有两个好处， 一个是可以减少 Translation Lookaside Buffer (TLB) 失误以提高性能 另一个是利用 huge page不会swap的特性保证MySQL的内存不会被交换到swap中
MySQL 5.0.3之后在linux上支持huge page，可以使用 large-page 选项启动MySQL。
mysql> select @@innodb_additional_mem_pool_size/1024/1024; +---------------------------------------------+ | @@innodb_additional_mem_pool_size/1024/1024 | +---------------------------------------------+ | 8.00000000 | +---------------------------------------------+ 1 row in set (0.00 sec)
mysql> select @@innodb_buffer_pool_size/1024/1024; +-------------------------------------+ | @@innodb_buffer_pool_size/1024/1024 | +-------------------------------------+ | 200.00000000 | +-------------------------------------+ 1 row in set (0.00 sec)
mysql> select @@tmp_table_size/1024/1024; +----------------------------+ | @@tmp_table_size/1024/1024 | +----------------------------+ | 16.00000000 | +----------------------------+ 1 row in set (0.18 sec)
mysql> select @@innodb_log_buffer_size/1024/1024; +------------------------------------+ | @@innodb_log_buffer_size/1024/1024 | +------------------------------------+ | 8.00000000 | +------------------------------------+ 1 row in set (0.00 sec)
mysql> select @@max_heap_table_size/1024/1024; +---------------------------------+ | @@max_heap_table_size/1024/1024 | +---------------------------------+ | 16.00000000 | +---------------------------------+ 1 row in set (0.00 sec)
内存和:sum (MB)
select
@@innodb_additional_mem_pool_size/1024/1024+@@innodb_buffer_pool_size/1024/1024+@@tmp_table_size/1024/1024+@@innodb_log_buffer_size/1024/1024+@@max_heap_table_size/1024/1024
计算多少个大页
sum/2=124.0000
增加几个页: 130页
[root@localhost ~]# echo 130 > /proc/sys/vm/nr_hugepages
8个buffer poll
mysql> select @@innodb_buffer_pool_instances; +--------------------------------+ | @@innodb_buffer_pool_instances | +--------------------------------+ | 8 | +--------------------------------+ 1 row in set (0.00 sec)
kernel.shmmax=130/8=17m 换成字节：17*1024=17408
kernal.shmall:整个系统范围可用的共享内存页的总数=130个页
[root@localhost ~]# id mysql
uid=502(mysql) gid=503(mysql) 组=503(mysql)
vi /etc/sysctl.conf
kernel.shmmni = 4096
vm.nr_hugepages=130 vm.hugetlb_shm_group=503
sysctl -w
vi /etc/security/limits.conf
@mysql soft memlock unlimited @mysql hard memlock unlimited
my.cnf
[mysqld]
large-pages
这个指定总共huge page的页数，可以放到/etc/rc.local中。由于分配时需要有连续的内存空间，所以如果在运行了一段时间的系统上执行，可能无法分配到指定的数量，即使还有足够的内存。 之后还需要设置内核参数kernel.shmmax和kernel.shmall，否则MySQL启动时会报22的错误 InnoDB: HugeTLB: Warning: Failed to allocate 536887296 bytes. errno 22 shmall是共享内存的总大小，单位是页，默认2097152（8G）。可以使用sysctl -w或者在/etc/sysctl.conf中设置 除此还需要设max locked memory，使用ulimit -l或设置/etc/security/limits.conf，否则会报12的错误： Warning: Failed to allocate 31457280 bytes from HugeTLB memory. errno 12
[root@localhost ~]# cat /proc/meminfo | grep -i huge HugePages_Total: 130 HugePages_Free: 130 HugePages_Rsvd: 4 HugePages_Surp: 0 Hugepagesize: 2048 kB
eg:
# Set the number of pages to be used. # Each page is normally 2MB, so a value of 20 = 40MB. # This command actually allocates memory, so this much # memory must be available. echo 20 > /proc/sys/vm/nr_hugepages # Set the group number that is permitted to access this # memory (102 in this case). The mysql user must be a # member of this group. echo 102 > /proc/sys/vm/hugetlb_shm_group # Increase the amount of shmem permitted per segment # (12G in this case). echo 1560281088 > /proc/sys/kernel/shmmax # Increase total amount of shared memory. The value # is the number of pages. At 4KB/page, 4194304 = 16GB. echo 4194304 > /proc/sys/kernel/shmall
ipcs -m -l
------ Shared Memory Limits --------
max number of segments = 4096
max seg size (kbytes) = 17
max total shared memory (kbytes) = 520
min seg size (bytes) = 1