Linux性能调优之内存调优

内存的调优

 

1.内存测试

安装内存测试软件:memtest

rpm -ivh /media/Packages/memtest86+-4.10-2.el6.x86_64.rpm

 

内存测试:

memtest-setup

 

执行结果查看:

cat /etc/grub.conf //启动项已经添加了一个启动选项

# grub.conf generated by anaconda

#

# Note that you do not have to rerun grub after making changes to this file

# NOTICE:  You have a /boot partition.  This means that

#          all kernel and initrd paths are relative to /boot/, eg.

#          root (hd0,0)

#          kernel /vmlinuz-version ro root=/dev/sda2

#          initrd /initrd-[generic-]version.img

#boot=/dev/sda

default=1

timeout=5

splashimage=(hd0,0)/grub/splash.xpm.gz

hiddenmenu

title Memtest86+ (4.10)

    root (hd0,0)

    kernel --type=netbsd /elf-memtest86+-4.10

title Red Hat Enterprise Linux(2.6.32-431.el6.x86_64)

    root(hd0,0)

    kernel/vmlinuz-2.6.32-431.el6.x86_64 ro root=UUID=1760ae83-ad1c-48dd-8785-915950691d72 rd_NO_LUKS rd_NO_LVM LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet

    initrd/initramfs-2.6.32-431.el6.x86_64.img

 reboot

Linux性能调优之内存调优_第1张图片

Linux性能调优之内存调优_第2张图片 

 

 

 

2.内存缓存

 

BUFFER 索引缓存 缓存 写时用,先写入到内存

CACHE 页缓存 快取 读时用,先读入到内存

buffers #缓存从磁盘读出的内容,这种理解是片面的

cached #缓存需要写入磁盘的内容,这种理解是片面的

终端1:[root@localhost ~]# free -m

终端2:[root@localhost ~]# find /   

CACHE:页缓存, 内存页是内存中的最小存储单位,一页尺寸4kB

对象文件系统  块block 1kB 2kB 4kB

  扇区sectors 512b

终端1: [root@localhost ~]# free -m //查看  buffer 增长

            total       used       free     shared    buffers     cached

Mem:       1004412     462792     541620          0      27892     190344

-/+ buffers/cache:     244556     759856

Swap:      1048568          0    1048568

 

手动清空buffer+cache :

 

查看缓存

[root@localhost ~]# cat /proc/sys/vm/drop_caches    //默认是 0

[root@localhost ~]# free –m

             total       used       free     shared    buffers     cached

Mem:          1137        783        353          0         67        411

-/+ buffers/cache:        303        833

Swap:          999          0        999

 

清空缓存:

sync

#内存和硬盘的数同步,内存数据写入硬盘

echo 1 > /proc/sys/vm/drop_caches

#清空缓存

 

查看清空结果

[root@localhost ~]# free -m

             total       used       free     shared    buffers     cached

Mem:          1137        367        770          0          0         67

-/+ buffers/cache:        299        838

Swap:          999          0        999

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