cdm probe shows wrong Physical Memory on AIX and Linux Servers
Article ID: 47141
Updated On:
Products
Issue/Introduction
cdm probe shows different Physical Memory on AIX and Linux Servers and not sure why.
Environment
- Release: Any UIM Version
- Component: Any cdm probe version after 5.01
Cause
- For this metric, the buffer cache will be subtracted from physical memory value if the key mem_buffer_used is set as no. This is the default value.
- This support is added for Linux, AIX, Solaris and HPUX platforms.
Resolution
UNIX/Linux Systems
To include the buffer and cache memory for physical memory calculation (by not subtracting it in the calculation), set the value of mem_buffer_used key to yes in the Raw Configuration for the cdm probe.
- Open the cdm Raw Configuration.
- Expand the Setup section of the configuration
- Edit the mem_buffer_used key and change it to yes
- Save the configuration
- Deactivate/Activate the probe
Additional Information
The mem_buffer_used parameter is only applicable to Unix/Linux systems (Linux, Solaris, HP-UX, and AIX).
On Windows, this setting has no effect because there is no equivalent calculation performed to exclude cache from the "used" memory value.
To meet the requirement of excluding cached memory from the "in use" calculation on Windows, we recommend using the User Memory Utilization (%) metric. This represents the percentage of memory in use excluding cache, calculated as:
UserUsed = TotalPhys - (Available + SystemUsed)
Since SystemUsed includes the system file cache (such as System Cache Resident Bytes), cache memory is not counted as "user" memory. This metric aligns with the need to exclude cache from memory usage calculations.
The following formulas for QOS_MEMORY_PHYSICAL are used:
- When mem_buffer_used = no
QOS_MEMORY_PHYSICAL (Physical Memory Used MB) = (MemTotal - MemFree - Buffers - Cached) /1024
- When mem_buffer_used = yes
QOS_MEMORY_PHYSICAL (Physical Memory Used MB) = (MemTotal - MemFree) /1024
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