On Sat, Mar 18, 2017 at 07:15:29PM +0100, David Lowe wrote:
> On 2017-03-18 09:28, Otto Moerbeek wrote:
> > On Fri, Mar 17, 2017 at 01:04:29PM +0200, Mihai Popescu wrote:
> >
> > > Hello,
> > >
> > > I am using top to show running programs activity on an OpenBSD system.
> > >
> > > Is there another better command to show in detail the memory used by
> > > programs?
> > >
> > > My system has 8GB physical RAM. Looking at this, can someone tell me
> > > if OpenBSD uses the "swap memory" model used by other OSes, basically
> > > moving chunks from physical memory to the swap partition when they are
> > > not used?
> >
> > Pages in physical memory are paged out to swap space, if thery are not
> > actively used *and* there is general shortage of physical memory. If
> > physical memory is not tight, no swapping will occur.
> >
> > >
> > > If a program ask for a memory allocation, is this request satisfied
> > > imediately if there is enough physical RAM available or is it done at
> > > the moment the program needs to do read/write on that memory?
> >
> > Virtual memory is allocated subject to per process ulimits and general
> > platform limitation but not touched on allocation. Only when the
> > virtual pages are referred to they will become backed by physical
> > pages. These pages might be paged out to swap if need be.
> >
> > >
> > > Expanding the first question, is there a command to show all these
> > > details, like total memory used, static and dynamic, how much is
> > > physical or swap, etc?
> >
> > top shows two columns: SIZE and RES. SIZE is the total virtual memory
> > used by a process (executable, stack and data). RES are the total
> > physical pages in use by a process. Both columns can be deceptive
> > since e.g. memory can be shared by multiple processes. There are also
> > things like dynamically loaded libraries that complicate matters.
> >
> > procmap can show a lot of details about a process, but that's maybe
> > too much for your purpose. It also is disabled in a default setup.
> >
> > but:
> >
> > $ ps -axO tsiz,dsiz,ssiz,vsz,rss,maxrss,%mem,lim
> >
> > Will show you most of the details you're after. See the man page for
> > some explanation.
> >
> > Note: the SIZE and RES columns from top are called vsz and rss in ps,
> > text is the name fthe executable program code.
>
> Thanks for the explanation!
> May I ask why I am getting RES > SIZE sometimes?
>
> Here is one line as example:
> 5411 d.lowe 2 0 12M 16M sleep/2 kqread 5:32 0.00% tmux
My guess would be shared libs,
-Otto
