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When Memory Usage per Process is High

Document Type | Troubleshooting

Category | Monitoring/Inspection

Applicable Product Versions | 5SP1FS01, 5SP1FS02, 5SP1FS03, 5SP1FS04, 5SP1FS06, 6FS01, 6FS02, 6FS03, 6FS04, 6FS05, 6FS06, 6FS07, 6FS07PS, 7FS01, 7FS02, 7FS02PS

Document Number | TMOTS019

 

Issue

When monitoring with ps aux or top, the memory usage may appear larger than the actual memory usage.

Example) The VSZ or RSS of each memory is large, and when all are summed, an inaccurate value that is several times the server memory is displayed.
[tibero1@prolinux1 sql]$ ps aux --sort -rss
USER         PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
tibero1     1766  0.0  1.9 3103216 73776 pts/0   Sl   00:01   0:01 tbsvr_FGWP000  -t NORMAL -SVR_SID DB1_node1
(omitted)
tibero1     1768  0.0  0.6 2495088 23208 pts/0   Sl   00:01   0:00 tbsvr_PEWP000  -t NORMAL -SVR_SID DB1_node1
tibero1     1773  0.0  0.6 2495088 23052 pts/0   Sl   00:01   0:00 tbsvr_PEWP005  -t NORMAL -SVR_SID DB1_node1
tibero1     1769  0.0  0.6 2495088 23008 pts/0   Sl   00:01   0:00 tbsvr_PEWP001  -t NORMAL -SVR_SID DB1_node1
tibero1     1772  0.0  0.6 2495088 23000 pts/0   Sl   00:01   0:00 tbsvr_PEWP004  -t NORMAL -SVR_SID DB1_node1
 
 
 

Cause

Since Tibero uses shared memory, memory usage displayed by ps or top includes the shared memory area. Therefore, the memory usage shown is the sum of both the actual used memory and the shared memory.

 

 

Solutions

In Linux and Solaris environments, you can check the actual memory usage distribution and shared memory using pmap; on AIX, use procmap.

Example of Checking Memory

[tibero1@prolinux1 sql]$ pmap -x 1766
1766:   tbsvr_FGWP000  -t NORMAL -SVR_SID DB1_node1
Address           Kbytes     RSS   Dirty Mode  Mapping
0000000000400000  152244   26396       0 r-x-- tbsvr
0000000009aad000     220     216       4 r---- tbsvr
0000000009ae4000    3160    2604      96 rw--- tbsvr
0000000009dfa000     884     196     196 rw---   [ anon ]
(omitted)
00007fbfeeff7000      32       0       0 ----- zero
(omitted)
00007fbff4197000 2097152   32576   32576 rw-s-   [ shmid=0x0 ]
00007fc074197000    1776    1424       0 r-x-- libc-2.28.so
(omitted)
ffffffffff600000       4       0       0 r-x--   [ anon ]
---------------- ------- ------- -------
total kB         3103220   75028   42332
The size 2097152 at address 00007fbff4197000 is shared memory with shmid=0x0. The remainder after subtracting this value from the total is the space actually used separately by the process.
 
Also, it can be confirmed as below that the shared memory actually exists with id 0 (shmid), the size is the same (bytes=2147483648 - 2097152 KB), and 15 processes are sharing it (nattch 15).
[tibero1@prolinux1 sql]$ ipcs -m

------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status
0x1553710c 0          tibero1    640        2147483648 15
Caution
Perform this according to the guidance of Tmax Tibero Technical Support.

 

 

 

 

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