On a new PC with 64 GB of main memory, I can only see about 60 GB, missing a whole 4 GB.
In BIOS all four modules of 16 GB each can be seen, and also that it adds up to the expected 64 GB.
But on Linux, I only see
$ free total used free shared buff/cache available Mem: 63726408 1917044 57576532 156680 4232832 60936548 Swap: 33554428 0 33554428
$ grep MemTotal /proc/meminfo MemTotal: 63726408 kB
which is around 60.77 GB of main memory.
Seeing this, I looked at my previous machine with 16 GB of main memory. Here too, one GB of the whole 16 GB is missing, leaving only 15.1 GB.
So, where and why are these 5-6% of main memory missing?
Addressing the possible duplicate How do I read from /proc/$pid/mem under Linux?
My question is not about a single process memory, but all system memory, especially missing so much of it.