Hot answers tagged memory
There are several reasons a piece of RAM would not be used by Linux: If Linux detects it as belonging to a hardware peripheral. Most computers need RAM for the display, and thus reserve some RAM for the graphics card. It's also possible for the graphics card to contain its own RAM; as graphics cards have relatively high memory requirements, they tend not ...
Arch Linux' kernel has the swap accounting disabled by default (cf. the kernel config file). You can enable it by booting with swapaccount=1 in your kernel cmdline (cf. the kernels Kconfig documentation.
The names actually match up, but sar and free don't show exactly the same fields. Your first ??? isn't kbcommit, it's shared memory, the same as Shmem from /proc/meminfo. The second row shows the memory usage if the memory used by buffers and cache was treated as free rather than used. $ free total used free shared buffers ...
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