What is PSS of a process?

Answer

The “proportional set size” or PSS of process is the sum of the unshared memory of a process and the proportion of memory shared with other processes.

Formula: unshared memory of a process + (memory shared with other processes /number of processes that share memory)

We’ll understand through an example

Example

• Process A has 100 KiB of unshared memory
• Process B has 200 KiB of unshared memory
• Both process A and process B have 150 KiB of the same shared memory region
• There are 2 processes

Now, the PSS for these two processes are as follows:

• PSS of process A = 100 KiB + (150 KiB / 2) = 175 KiB
• PSS of process B = 200 KiB + (150 KiB / 2) = 275 KiB