Oracle HugePages没有被使用导致服务器很卡的解决方法

原因：
通过用户反应使用起来很卡，接到故障报告后，登录服务器需要差不多1分钟才能连接上去，先简单的看一下服务器的性能状况，发展IO极低、内存剩余还比较多，至少还有1GB以上，也没有page in / page out，而最显著的现象就是CPU利用率相当地高，一直保持在100%，同时CPU利用率的SYS部分，均在95%以上，因物理内存不足，正在不断的进行页面交换，使用swap空间。

通过查看oracle alert日志发现大页内存没有被使用
view alert.log

Starting ORACLE instance (normal)************************ Large Pages Information *******************
Per process system memlock (soft) limit = 64 KB
Total Shared Global Region in Large Pages = 0 KB (0%)

Large Pages used by this instance: 0 (0 KB)
Large Pages unused system wide = 15362 (30 GB)
Large Pages configured system wide = 15362 (30 GB)Large Page size = 2048 KB
RECOMMENDATION:
  Total System Global Area size is 30 GB. For optimal performance,
  prior to the next instance restart:  1. Large pages are automatically locked into physical memory.
 Increase the per process memlock (soft) limit to at least 30 GB to lock 100% System Global Area's large pages into physical memory
********************************************************************

解决步骤：
1.检查是否设置HugePages
cat /etc/sysctl.conf

cat /etc/sysctl.conf
net.core.rmem_default = 262144
net.core.rmem_max = 4194304
net.core.wmem_default = 262144
net.core.wmem_max = 1048576

vm.nr_hugepages = 15362

结果：有配置HugePages

2.查看是否设置memlock unlimited

#<domain>      <type>  <item>         <value>
#

#*               soft    core            0
#*               hard    rss             10000
#@student        hard    nproc           20
#@faculty        soft    nproc           20
#@faculty        hard    nproc           50
#ftp hard nproc 0
#@student        -       maxlogins       4

*      soft    nofile    131072
*      hard    nofile    131072
*      soft    nproc    131072
*      hard    nproc    131072

结果： 没有加上
处理方法：在末尾加上oracle soft memlock unlimited oracle hard memlock unlimited

3.重启数据库、重启机器。
查看对应alert日志中会有“Large Pages Information”内容：
cat alert.log | grep -A 3 “Large Pages Information”

-- 没有设置unlimited之前日志
oracle soft memlock unlimited
oracle hard memlock unlimited
************************ Large Pages Information *******************
Per process system memlock (soft) limit = 64 KB

--设置memlock unlimited之后的日志
Total Shared Global Region in Large Pages = 0 KB (0%)
--
************************ Large Pages Information *******************
Per process system memlock (soft) limit = UNLIMITED

Total Shared Global Region in Large Pages = 30 GB (100%)

4.确认HugePages设置成功
查看关于HugePages的信息：

[[email protected] ~]$ grep Huge /proc/meminfo
AnonHugePages:      6144 kB
HugePages_Total:   15362
HugePages_Free:      563
HugePages_Rsvd:      562
HugePages_Surp:        0
Hugepagesize:       2048 kB

**结果：**从日志和grep Huge /proc/meminfo来看HugePages已正常使用，服务器也恢复正常。