Red Hat ENTERPRISE LINUX AS 2.1 - Guide d'installation télécharger pdf (Page 53)

Huge Pages and Shared Memory File System in Red Hat Enterprise Linux 3

On this database system the size of the database buffer cache is 2 GB:

db_block_buffers = 262144

db_block_size = 8192

The following command shows that Oracle allocated a shared memory file of 2GB

(262144*8192=2147483648) for the buffer cache on the ramfs shared memory file system:

# mount | grep ramfs

ramfs on /dev/shm type ramfs (rw)

# ls -al /dev/shm

total 204

drwxr-xr-x 1 oracle dba 0 Oct 30 16:00 .

drwxr-xr-x 22 root root 204800 Oct 30 16:00 ..

-rw-r----- 1 oracle dba 2147483648 Nov 1 16:46 ora_orcl1_1277954

The next command shows how many Huge Pages are currently being used on this system:

$ grep Huge /proc/meminfo

HugePages_Total: 1536

HugePages_Free: 194

Hugepagesize: 2048 kB

The output shows that 1342 (1536-194) Huge Pages are being used. This translates into 2814377984

(1342*2048*1024) bytes being allocated in the Huge Pages pool. This number matches the size

of both shared memory segments (2736783360+77594624=2814377984) displayed by the ipcs

command above.

This shows that the Huge Pages pool is not being used for the ramfs shared memory file system.

Hence, you do not need to increase the Huge Pages pool if you use the ramfs shared memory file

system.

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Red Hat ENTERPRISE LINUX AS 2.1 - Guide d'installation Page 53