RHEL3设置HugePages / HugeTLB的推荐值

  在RHEL3上配置大内存的时候需要设置 HugeTLB，这里解释一种简单的方法来找到合理的推荐值：

  首先建立一个hugepages_settings.sh的shell文件，文件的内容如下：

 

#!/bin/bash
#
# hugepages_settings.sh
#
# Linux bash script to compute values for the
# recommended HugePages/HugeTLB configuration
#
# Note: This script does calculation for all shared memory
# segments available when the script is run, no matter it
# is an Oracle RDBMS shared memory segment or not.

# Check for the kernel version
KERN=`uname -r | awk -F. '{ printf("%d.%d\n",$1,$2); }'`

# Find out the HugePage size
HPG_SZ=`grep Hugepagesize /proc/meminfo | awk {'print $2'}`

# Start from 1 pages to be on the safe side and guarantee 1 free HugePage
NUM_PG=1

# Cumulative number of pages required to handle the running shared memory segments
for SEG_BYTES in `ipcs -m | awk {'print $5'} | grep "[0-9][0-9]*"`
do
   MIN_PG=`echo "$SEG_BYTES/($HPG_SZ*1024)" | bc -q`
   if [ $MIN_PG -gt 0 ]; then
      NUM_PG=`echo "$NUM_PG+$MIN_PG+1" | bc -q`
   fi
done

# Finish with results
case $KERN in
   '2.4') HUGETLB_POOL=`echo "$NUM_PG*$HPG_SZ/1024" | bc -q`;
          echo "Recommended setting: vm.hugetlb_pool = $HUGETLB_POOL" ;;
   '2.6') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;;
    *) echo "Unrecognized kernel version $KERN. Exiting." ;;
esac

# End

然后执行这个shell，会得到一个相应的结果，如：

$ ./hugepages_settings.sh
Recommended setting: vm.nr_hugepages = 67
再实现sysctl -w vm.hugetlb_pool 命令设置核心参数（RHEL5里好像没这个参数了），

之后用grep Huge /proc/meminfo命令检查HugePages是否被激活，如果装了数据库，重启一下看看meminfo有没什么变化。

如果没有生效可能需要重启一下系统了。