Glossary
Physical footprint
The memory a process is responsible for, including its compressed memory.
What it is
Physical footprint is the kernel's measure of how much memory a single process is charged for: its private memory in RAM plus the part of it that has been compressed. Memory shared with other processes, such as system libraries, isn't counted in full.
It is a better measure of “how much memory does this process cost?” than resident size, which also counts shared memory and hides compressed memory.
Why it matters
Per-process numbers don't add up to an app's real cost when the app runs dozens of helper processes. You need the footprint of every process that belongs to the app.
In Activity Monitor
The Memory column in the Memory tab, one row per process.
In iKnowMyMac
Each app row adds up the memory of every process that belongs to it, so Chrome or an Electron app shows one total. Expand the row to see each process.
footprint <pid>Prints the footprint of one process, broken down by memory type.
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