How is Memory Utilization calculated for Linux server?
Formula :
Memory Utilization (%) = 100 -(((MemFree + Buffers + Cached)*100)/maxValue)
In Telnet/SSH mode:
We are using free -b command to get the memory usage for Linux server. Assume the output below,
# free -b
total used free shared buffers cached
Mem: 18787995648 18667773952 120221696 0 95801344 9579597824
-/+ buffers/cache: 8992374784 9795620864
Swap: 18876977152 352256 18876624896
Memory Utilization (%) = 100 -(((MemFree + Buffers + Cached)*100)/maxValue)
Memory Utilization (%) = 100 - (((120221696+95801344+9579597824)*100)/18787995648) =979562086400/18787995648 = 100 - 52.13 = 47.87 = 48% (Rounded value)
Memory Utilization (MB) = maxValue-(MemFree + Buffers + Cached)
Memory Utilization (MB) = 18787995648 - (120221696+95801344+9579597824)
= 18787995648 - 9795620864
= 8992374784 This is Bytes.
To convert this is MB = 8992374784/(1024/1024) = 8575MB
In SNMP mode:
We are using UCD-SNMP-MIB file to get memory usage for Linux servers. OID's used for,
Total Memory .1.3.6.1.4.1.2021.4.5.0
Free Memory .1.3.6.1.4.1.2021.4.6.0
Buffer Memory .1.3.6.1.4.1.2021.4.14.0
Cached Memory .1.3.6.1.4.1.2021.4.15.0
Memory Utilization (%) = 100 -(((MemFree + Buffers + Cached)*100)/maxValue)
In Telnet/SSH mode:
We are using free -b command to get the memory usage for Linux server. Assume the output below,
# free -b
total used free shared buffers cached
Mem: 18787995648 18667773952 120221696 0 95801344 9579597824
-/+ buffers/cache: 8992374784 9795620864
Swap: 18876977152 352256 18876624896
Memory Utilization (%) = 100 -(((MemFree + Buffers + Cached)*100)/maxValue)
Memory Utilization (%) = 100 - (((120221696+95801344+9579597824)*100)/18787995648) =979562086400/18787995648 = 100 - 52.13 = 47.87 = 48% (Rounded value)
Memory Utilization (MB) = maxValue-(MemFree + Buffers + Cached)
Memory Utilization (MB) = 18787995648 - (120221696+95801344+9579597824)
= 18787995648 - 9795620864
= 8992374784 This is Bytes.
To convert this is MB = 8992374784/(1024/1024) = 8575MB
In SNMP mode:
We are using UCD-SNMP-MIB file to get memory usage for Linux servers. OID's used for,
Total Memory .1.3.6.1.4.1.2021.4.5.0
Free Memory .1.3.6.1.4.1.2021.4.6.0
Buffer Memory .1.3.6.1.4.1.2021.4.14.0
Cached Memory .1.3.6.1.4.1.2021.4.15.0
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