CODEWITHSUNDEEP
linuxmemorymemory-management
Mandar
Mandar

Reputation: 733

Memory usage analysis

I was performing an activity wherein i had to calculate the total memory used by the system, and then give the accounting for the total used memory in terms of processes and other entities.

I used /proc/meminfo to get total used memory (Total Usable Mem - Total Free Mem). Then listed out all the processes and there individual memory usage. But both figures didnt match which was not what I expected to be. Even with the total memory used by all processes I was not able to get account for 7MB to used memory.

Am I missing any piece of information here ?

Upvotes: 0

Views: 786

Answers (2)

sehe
sehe

Reputation: 393009

Guessing that you <quote>listed out all the processes and there [sic] individual memory usage</quote> using ps you might be looking at

The SIZE and RSS fields don't count some parts of a process including the page tables, kernel stack, struct thread_info, and struct task_struct. This is usually at least 20 KiB of memory that is always resident. SIZE is the virtual size of the process (code+data+stack).

Upvotes: 1

spraff
spraff

Reputation: 33395

Shared libraries can mess up the figures. Processes can share memory directly. Some sections of memory are quietly reserved for hardware I/O mapping or other OS internals.

Upvotes: 0

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