Monitoring memory allocation

Use the od command of crash to get information about memory allocation on the system. The following commands print the values of the kernel variables that store information about memory allocation; the -d option is used to request that decimal values are displayed:

od -d availrmem

Number of 4KB pages of core memory available to user-level processes. This is equal to the total physical memory (physmem) excluding memory allocated to the kernel. It does not including swap space.

od -d availsmem

Number of 4KB pages of swappable memory available for use. For diskless clients, availsmem and availrmem have the same value; on other configurations, availsmem represents the unused portions of availrmem and nswap.

od -d freemem

Number of unused 4KB pages of core memory.

od -d nswap

Size of swap space, as a number of physical 512-byte disk blocks; divide this number by 8 to convert it to its equivalent in units of 4KB pages.

od -d physmem

Total number of 4KB physical memory pages configured on the system. This figure does not change. For example, a 32MB system shows 8096 for physmem. Some machines remap part of physical memory so that the kernel cannot locate it; on these machines, physmem will have a value lower than the actual physical memory configured on the system. The gap between 640KB and 1MB is an example of this.