Wired Memory

Hardware, drivers and system features all take some wired memory. Virtualization and some graphics work can add more. Since you cannot free it directly, the practical question is whether memory pressure is still green.

Quit apps that run virtual machines or other heavy system level work if you are not using them, and restart the Mac if wired memory seems unusually high after a long uptime. Do not remove system files or kernel extensions to try to reduce it.

You can see wired memory in Activity Monitor or in Terminal. Activity Monitor shows it only as a total for the whole Mac. There is no per-process wired memory column to add from View > Columns. The Terminal commands below only read information.

1. In Activity Monitor, click the Memory tab. Wired Memory is listed under Memory Used at the bottom of the window.
2. In Terminal, run top -l 1 | grep PhysMem. The line shows memory used, with the wired amount in parentheses, and how much is unused.
3. For a more detailed view, run vm_stat. The first line gives the page size, and Pages wired down is the number of wired pages. Multiply the two to get the amount in bytes.

Activity Monitor describes wired memory as physical memory containing data that cannot be compressed or swapped to disk. Things that commonly need it include:

• The macOS kernel and its own data.
• Drivers and kernel extensions for your hardware and accessories.
• Page tables, which the system uses to keep track of each process's memory.
• Memory an app has locked in RAM on purpose, which some apps do so their data is never moved out of memory.

No. The kernel_task row in the Memory column usually shows a much smaller figure than Wired Memory at the bottom of the window. Wired memory is counted system wide and is not charged to one process row, so you will not find the full amount by sorting the process list.

This is also why you cannot quit your way out of most wired memory. It is released when the part of the system that needs it no longer does.

Because wired memory cannot be compressed or moved to disk, every bit of it is RAM that apps cannot use. Apple lists wired memory as one of the inputs to memory pressure.

On a Mac with a lot of RAM, a large wired figure rarely makes a difference. On a Mac with less RAM, the same amount leaves less room for apps, so memory pressure turns yellow sooner. The fix is the same as for any memory shortage: run fewer heavy apps at once.

Normal: wired memory moves up and down a little as you connect devices, start and stop virtual machines, and use the Mac. It is a part of Memory Used on every Mac.

Worth checking: wired memory keeps growing over days while you run the same apps, and memory pressure starts turning yellow. Restart the Mac and watch whether it grows again. If it only grows when a certain accessory or driver is installed, check that software for an update or remove it with its own uninstaller. Apps that claim to free memory cannot release wired memory, because it has to stay in RAM.