On Tue, Dec 22, 2015 at 02:31:58AM +0800, Tinker wrote:
> Hi, on my 4GB RAM machine, top says
>
> "Memory: Real: 1293M/3786M act/tot Free: 158M Cache: 2079M Swap: 449M/10G"
>
> All the five first columns vary over time, in particular the first four.
>
> 3786 + 158 = 3944 is fairly close to 4GB so I guess that's the amount of RAM
> that the BIOS (+HW drivers?) actually left usable, so that number makes
> sense.
AFAIK:
tot: memory allocated by kernel
act: memory recently accessed, subset of tot.
free: memory not allocated
tot + free: total memory available
cache: pages allocated to buffer (filesystem) cache
all memory includes both kernel and memory used by processes.
-Otto
>
> The 158 number is fairly clear also - that's all the RAM that's not in use.
>
> And the 2079 number should be the total amount of filesystem cache.
>
> But then what are the first two numbers, and there in particular the second
> one??
>
> I guess the first one is the total amount of malloc():s (I guess including
> the actual malloc structures).
>
> But the second one makes no sense - 1293 (first column) + 2079 (fourth
> column) make 3372 so this number does not only cover malloc:s and the FS
> cache then, but there are 414MB of other stuff. Is it that the kernel with
> all of its work takes 414MB?? If so that's weird because really the machine
> doesn't do a lot.
>
> The "man" page doesn't say any of this.
>
> I think it's good to know this, for diagnostic purposes.
>
> Anyone knows what the second column is for?
>
> Thanks,
> Tinker
