Day: August 2, 2017

SITUATION

When investigating into client’s Oracle database performance issue, we found the swap space usage is constantly very high on this Linux server.

OS: RHEL 7.3
DB: Oracle 12.2.0.1

FINDINGS

1)top

Tasks: 352 total, 2 running, 350 sleeping, 0 stopped, 0 zombie
Cpu(s): 13.4%us, 4.1%sy, 0.0%ni, 79.3%id, 2.2%wa, 0.3%hi, 0.8%si, 0.0%st
Mem: 32172820k total, 32015956k used, 156864k free, 14528k buffers
Swap: 16777208k total, 7435428k used, 9341780k free, 11129844k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
137049 oracle 15 0 16.2g 5.3g 5.3g S 20.6 17.4 10:14.17 oracle
 72457 oracle 15 0 16.2g 4.7g 4.7g S 15.3 15.3 10:50.15 oracle
...
..
.

2) pmap

$ pmap -x 137049
137049: oracleRACTEST1 (LOCAL=NO)
Address          Kbytes   RSS     Dirty Mode Mapping
0000000000400000 96356    11704   0     r-x-- oracle
0000000006419000 444      140     4     rwx-- oracle
0000000006488000 148      100     80    rwx-- [ anon ]
000000001966e000 532      176     92    rwx-- [ anon ]
0000000060000000 16779264 5444888 1485768 rwxs- [ shmid=0x670005 ]
00000032b6a00000 112      108     0     r-x-- ld-2.5.so
00000032b6c1c000 4        0       0     r-x-- ld-2.5.so
...
..
.
00007fff4c504000 160 136 132 rwx-- [ stack ]
00007fff4c5d2000 12 4 0 r-x-- [ anon ]
ffffffffff600000 8192 0 0 ----- [ anon ]
---------------- ------ ------ ------
total kB 16954204 5477952 1490448

3) swappiness

$ cat /proc/sys/vm/swappiness
10