`top` process memory usage: SIZE vs RES

[Jesse Guardiani]

Dan Nelson wrote:

> In the last episode (Sep 12), Jesse Guardiani said:
>> Dan Nelson wrote:
>> > In the last episode (Sep 11), Jesse Guardiani said:
>> >  
>> >> 2.) What, exactly, is RES? `man top` describes it as this:
>> >>     "RES is the current amount of resident memory", but does
>> >>     that mean RES is included in SIZE? Or does that mean that
>> >>     RES should be counted in addition to SIZE?
>> > 
>> > RES the amount of SIZE that it currently in core
>> 
>> OK. To clarify, you mean core kernel memory here?
>> If so, how is that significant? Why should I care?
>> 
>> In other words, why would I ever want to know that?
> 
> core meaning physical memory; user memory in this case.

OK. And how does core, or user memory differ from SIZE memory
then? If X = SIZE - RES, where is X stored?


>  Processes can
> lock kernel memory, but there's no easy way of listing that (it's
> usually a small amount held in pipe or socket buffers and is
> short-lived). The name "core" came from when memory bits were ferrite
> rings magnetized by wires running through them.
> 
> http://www.columbia.edu/acis/history/core.html

Wow. That's a really cool bit of history. I don't quite understand
how a core is "switched", but I'm sure it must have worked.

-- 
Jesse Guardiani, Systems Administrator
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