Number of processor cores confusion

[Chris Green]

On Tue, Nov 10, 2020 at 04:40:43PM +0000, Colin Law wrote:
> On Tue, 10 Nov 2020 at 16:14, Chris Green <cl at isbd.net> wrote:
> > ..
> > Looking at gnome-system-monitor I can't really see how what is says
> > can be true, what sorts of things can *really* happen in parallel
> > without all sorts of problems?
> 
> Remember your foreground application is only one thing that is going
> on in the computer.  There are all sorts of background activities
> going on all the time which will run in parallel to your foreground
> app.  For example network activity, flushing disc buffers to disc,
> time sync, memory management, downloading system updates.  If you have
> browser pages open they often have background processes running and if
> at the same time you run a spreadsheet the browser processes keep
> going.  All of those will run in separate cores.
> 
THey can't, or at least a lot of them can't, they suffer from the same
issues as trying to multithread a single program.  Network activity
for example has to wait for something else to provide it with data (or
something to take data).  Memory management can't just come along and
move stuff about in memory while the kernel is doing something else. 

As pointed out by someone else here there are ways of doing it with
flags, semaphores, etc. but mostly this isn't implemented yet.


> Can you post an example of something in system monitor that you don't believe?
> 
There's not enough detail shown to really know what it's saying and
thus it's difficult/impossible to say "XYZ isn't right".

-- 
Chris Green