Installation guide

OCFS2 file systems.
Checking Asynchronous I/O Usage
To verify whether $ORACLE_HOME/bin/oracle was linked with async I/O, you can use the Linux com-
mands ldd and nm.
In the following example, $ORACLE_HOME/bin/oracle was relinked with async I/O:
$ ldd $ORACLE_HOME/bin/oracle | grep libaio
libaio.so.1 => /usr/lib/libaio.so.1 (0x0093d000)
$ nm $ORACLE_HOME/bin/oracle | grep io_getevent
w io_getevents@@LIBAIO_0.1
In the following example, $ORACLE_HOME/bin/oracle has NOT been relinked with async I/O:
$ ldd $ORACLE_HOME/bin/oracle | grep libaio
$ nm $ORACLE_HOME/bin/oracle | grep io_getevent
w io_getevents
If $ORACLE_HOME/bin/oracle is relinked with async I/O, it does not necessarily mean that Oracle is really
using it. You also need to ensure that Oracle is configured to use async I/O calls, see the Enabling Asyn-
chronous I/O Support section of this document.
To verify whether Oracle is making async I/O calls, you can examine the /proc/slabinfo file assuming
there are no other applications performing async I/O calls on the system. This file shows kernel slab cache in-
formation in real time.
Once Oracle makes async I/O calls, the output will look like this:
$ egrep "kioctx|kiocb" /proc/slabinfo
kioctx 64 110 384 10 1 : tunables 54 27 8 : slabdata 11 11
0
kiocb 3 15 256 15 1 : tunables 120 60 8 : slabdata 1 1
0
The numbers in red (number of active objects) show whether Oracle makes async I/O calls. The first column
displays the cache names kioctx and kiocb. The second column shows the number of active objects current-
ly in use.
To see kernel slab cache information in real time, you can also use the slabtop command:
$ slabtop
Active / Total Objects (% used) : 293568 / 567030 (51.8%)
Active / Total Slabs (% used) : 36283 / 36283 (100.0%)
Active / Total Caches (% used) : 88 / 125 (70.4%)
Active / Total Size (% used) : 81285.56K / 132176.36K (61.5%)
Minimum / Average / Maximum Object : 0.01K / 0.23K / 128.00K
OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
178684 78396 43% 0.12K 5764 31 23056K size-128
127632 36292 28% 0.16K 5318 24 21272K dentry_cache
102815 74009 71% 0.69K 20563 5 82252K ext3_inode_cache
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