Add a column showing the actual memory usage of a process (`RES` + `SWAP`)

[ishland]

Currently there's no way to quickly know the "actual" memory usage of a process other than adding RES + SWAP manually. As a side effect, there's also no way to sort by this and quickly know the memory hogging process. Sorting by either RES or SWAP individually doesn't really solve this issue.

It would be nice if htop adds a actual memory usage column for this for viewing and sorting.

[natoscott]

Does the change introduced in #492 meet your needs here?

[ishland]

Does the change introduced in #492 meet your needs here?

It does not, and it is even less accurate:

[natoscott]

OK, please suggest an alternative (PR) and discuss that with the folks who posted that original PR and are happy with it. Thanks!

[ugolnikovE]

I looked into the available memory metrics in the codebase. There are two possible approaches for a "total memory usage" column:

1. RES + SWAP - simple and cheap, both values are already available. However, this overcounts shared memory: if 10 processes use the same shared library, it's counted fully in each process's RES.
2. PSS + SwapPss - shared pages are divided proportionally among all processes using them, giving a more accurate per-process cost. htop already has the infrastructure to read both values.

I think option 2 would better match the goal of showing "actual memory usage" - would this work for your use case?

[ishland]

I think option 2 would better match the goal of showing "actual memory usage" - would this work for your use case?

That also works for my use case.

[ugolnikovE]

@natoscott would a PSS + SwapPss column be a welcome addition to the project?

[natoscott]

@ugolnikovE it makes sense to me - please open a PR and lets discuss with the other maintainers too. Thanks!