[20160517]11G HugePage的使用问题2.txt
--昨天测试了HUGEPAGE的使用问题,自己也看了一些文档,从11.2.0.2,加入了参数use_large_pages.
SYS@book> @ &r/ver1
PORT_STRING VERSION BANNER
------------------- -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx 11.2.0.4.0 Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
SYS@book> show parameter use_large_pages
NAME TYPE VALUE
--------------- ------- -------
use_large_pages string TRUE
如果参数为True，那么当系统的HugePage被使用尽，只有small pages的情况下，SGA也会继续运行。此时，Oracle实例就运行在内存使用
混合模式(Mixed Mode)下。
如果参数为是Only，从含义上，表示Oracle实例只会使用HugePage作为内存使用。如果系统在AMM模式或者HugePage用尽的时候，数据库
就不能启动或者报错。
如果参数为是false,就不使用HugePage.
--使用HugePage好处多多,特别是现在内存大,连接用户多的情况下优势更加明显.
1.先测试use_large_pages=only的情况.
--我采用手工设置,版本11.2.0.4.
SYS@book> show parameter sga_
NAME TYPE VALUE
------------- ----------- -------
sga_max_size big integer 608M
sga_target big integer 0
SYS@book> show parameter db_cache_size
NAME TYPE VALUE
------------------------------------ ----------- ------
db_cache_size big integer 408M
SYS@book> show parameter shared_pool_size
NAME TYPE VALUE
------------------------------------ ----------- -------
shared_pool_size big integer 172M
--关闭数据库,设置vm.nr_hugepages = 200.
SYS@book> startup nomount
ORACLE instance started.
Total System Global Area 634732544 bytes
Fixed Size 2255792 bytes
Variable Size 197133392 bytes
Database Buffers 427819008 bytes
Redo Buffers 7524352 bytes
SYS@book> alter system set use_large_pages=only scope=spfile ;
System altered.
SYS@book> shutdown immediate ;
ORA-01507: database not mounted
ORACLE instance shut down.
SYS@book> startup
ORA-27137: unable to allocate large pages to create a shared memory segment
Linux-x86_64 Error: 12: Cannot allocate memory
Additional information: 624951296
Additional information: 1
--我设置vm.nr_hugepages=200,也就是400M,不够数据库启动,报错.修改参数回来.
2.测试use_large_pages=true的情况.
SYS@book> create pfile='/tmp/a.ora' from spfile;
File created.
--删除use_large_pages那行.
SYS@book> create spfile from pfile='/tmp/a.ora' ;
File created.
SYS@book> startup nomount
ORACLE instance started.
Total System Global Area 634732544 bytes
Fixed Size 2255792 bytes
Variable Size 197133392 bytes
Database Buffers 427819008 bytes
Redo Buffers 7524352 bytes
$ cat /proc/meminfo | grep -i huge
AnonHugePages: 18432 kB
HugePages_Total: 200
HugePages_Free: 99
HugePages_Rsvd: 99
HugePages_Surp: 0
Hugepagesize: 2048 kB
************************ Large Pages Information *******************
Per process system memlock (soft) limit = 51 GB
Total Shared Global Region in Large Pages = 400 MB (65%)
Large Pages used by this instance: 200 (400 MB)
Large Pages unused system wide = 0 (0 KB)
Large Pages configured system wide = 200 (400 MB)
Large Page size = 2048 KB
RECOMMENDATION:
Total System Global Area size is 610 MB. For optimal performance,
prior to the next instance restart:
1. Increase the number of unused large pages by
at least 105 (page size 2048 KB, total size 210 MB) system wide to
get 100% of the System Global Area allocated with large pages
********************************************************************
--仅仅使用400*65/100=260M,提示增加105就ok了.
3.设置更小vm.nr_hugepages=50看看.
# cat /proc/meminfo | grep huge -i
AnonHugePages: 8192 kB
HugePages_Total: 50
HugePages_Free: 50
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
SYS@book> startup nomount
ORACLE instance started.
Total System Global Area 634732544 bytes
Fixed Size 2255792 bytes
Variable Size 197133392 bytes
Database Buffers 427819008 bytes
Redo Buffers 7524352 bytes
$ cat /proc/meminfo | grep -i huge
AnonHugePages: 20480 kB
HugePages_Total: 50
HugePages_Free: 24
HugePages_Rsvd: 24
HugePages_Surp: 0
Hugepagesize: 2048 kB
************************ Large Pages Information *******************
Per process system memlock (soft) limit = 51 GB
Total Shared Global Region in Large Pages = 100 MB (16%)
Large Pages used by this instance: 50 (100 MB)
Large Pages unused system wide = 0 (0 KB)
Large Pages configured system wide = 50 (100 MB)
Large Page size = 2048 KB
RECOMMENDATION:
Total System Global Area size is 610 MB. For optimal performance,
prior to the next instance restart:
1. Increase the number of unused large pages by
at least 255 (page size 2048 KB, total size 510 MB) system wide to
get 100% of the System Global Area allocated with large pages
********************************************************************
--仅仅使用400*16/100=16M,提示增加255就ok了.
--有了这些提示修改就方便了.修改为vm.nr_hugepages = 305就正好合适.
************************ Large Pages Information *******************
Per process system memlock (soft) limit = 51 GB
Total Shared Global Region in Large Pages = 610 MB (100%)
Large Pages used by this instance: 305 (610 MB)
Large Pages unused system wide = 0 (0 KB)
Large Pages configured system wide = 305 (610 MB)
Large Page size = 2048 KB
********************************************************************
# cat /proc/meminfo | grep huge -i
AnonHugePages: 26624 kB
HugePages_Total: 305
HugePages_Free: 94
HugePages_Rsvd: 94
HugePages_Surp: 0
Hugepagesize: 2048 kB
--有一些概念还是不清楚,这个的HugePages_Free表示什么,还没用吗?如果在数据库做一些操作HugePages_Free会减少.视乎不受一次分配
--到位的.
# cat /proc/meminfo | grep huge -i
AnonHugePages: 36864 kB
HugePages_Total: 305
HugePages_Free: 81
HugePages_Rsvd: 81
HugePages_Surp: 0
Hugepagesize: 2048 kB
