# Memory Widget

The memory widget provides a visual representation of RAM and swap usage over time.

<figure>
    <img src="../../../assets/screenshots/memory.webp" alt="A picture of an expanded memory widget."/>
</figure>

## Features

The legend displays the current usage in terms of percentage and actual usage in binary units (KiB, MiB, GiB, etc.).
If the total RAM or swap available is 0, then it is automatically hidden from the legend and graph.

One can also adjust the displayed time range through either the keyboard or mouse, with a range of 30s to 600s.

This widget can also be configured to display Nvidia and AMD GPU memory usage (`--disable_gpu` on Linux/Windows to disable) or cache memory usage (`--enable_cache_memory`).

## Key bindings

Note that key bindings are generally case-sensitive.

| Binding   | Action                                  |
| --------- | --------------------------------------- |
| ++plus++  | Zoom in on chart (decrease time range)  |
| ++minus++ | Zoom out on chart (increase time range) |
| ++equal++ | Reset zoom                              |

## Mouse bindings

| Binding      | Action                                                         |
| ------------ | -------------------------------------------------------------- |
| ++"Scroll"++ | Scrolling up or down zooms in or out of the graph respectively |

## How are memory values determined?

### Linux

Memory usage is calculated using the following formula based on values from `/proc/meminfo` (based on [htop's implementation](https://github.com/htop-dev/htop/blob/976c6123f41492aaf613b9d172eef1842fb7b0a3/linux/LinuxProcessList.c#L1584)):

```
MemTotal - MemFree - Buffers - (Cached + SReclaimable - Shmem)
```

You can find more info on `/proc/meminfo` and its fields [here](https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/deployment_guide/s2-proc-meminfo).

### Windows

In Windows, we calculate swap by querying `Get-Counter "\Paging File(*)\% Usage"`. This
is also what some libraries like [psutil](https://github.com/giampaolo/psutil/blob/master/psutil/arch/windows/mem.c) use. However, note there are also a few other valid methods of
representing "swap" in Windows (e.g. using `GetPerformanceInfo`), which all slightly don't
match.
