[NCLUG] Choppy performance issues.

[Bob Proulx]

John Gilmore wrote:
> Maybe it's a video driver issue? Pretty odd one, if so.

Have you made any forward progress?  I think there was little input
because no one had any idea what would be a problem.

Usually when I hear about such performance issues I think that the
system might be swapping.

You said you had a quad-core with 4G of ram.  (That is better than my
laptop.)  Your top showed that you had no swap used.

I know you have already tried looking for several things but let me
just say a few things about what I look for when I am looking for
system performance problems.  Maybe there will be something new in
there somewhere.

I like the 'htop' tool best.  It provides a nice bar graph of system
performance information specifically the "Mem" graph.  The regular top
shows the same information numerically but having it shown as a chart
is useful to me.  My system shows this right now.

  Mem[|||||||||||||||||||1602/3861MB]
      ^^^^^^^^^^^^^green
  Mem[|||||||||||||||||||1602/3861MB]
                   ^^^^^^blue
  Mem[|||||||||||||||||||1602/3861MB]
                         ^^^^^^^^^yellow


That is a relatively healthy system with half of the memory (green)
being consumed by userland processes.  The other half is mostly being
used for I/O buffers (blue) and file system buffer cache (yellow).
Only a very small part is actually "free" memory which is good because
free memory is not working for you.

A system in a bad state will be something more like this.

  Mem[|||||||||||||||||||3082/3861MB]
      ^^^^^^^^^^^^^^^^^^^^^^^^^green

The entire memory is being used by userland processes as shown by the
green part of the bar.  The numbers are used/total.  There is very
little blue and yellow for IO and file system buffer cache.  Such a
system isn't swapping yet.  But such a system will operate very slowly
because it will be running at file system disk drive speeds.  Without
ram caching everything will need to be written all of the way to disk.
Things are swapping but neither are they happy.

If I do suspect swapping I run 'vmstat' and look at the si/so
(swapin/swapout) fields.  If those are 0 or 1 that is fine.  If they
are large numbers such as 20 then that would indicate a high swap
rate.  Again I know you showed that you weren't using swap at all so I
don't suspect this to be anything but zero for you but I mention it
for the times when it might be non-zero.

Next I will look at 'iotop'.  It is like top but for I/O usage.  It
will show what processes are writing to disk.  Even a system in an
otherwise happy memory state may be consume all available bus
bandwidth and therefore running slowly.  Tasks may be waiting for I/O
to complete.  This is often indicated by a sluggish system with a high
cpu load average but with top not showing any processes using any cpu
time.  No cpu time is used when a process is blocked waiting for I/O.

For my desktop with 4G of ram I find it still gets into memory stress
solely due to my web browsers consuming memory.  If I find my system
suffering memory stress I usually first close all of my web browsers.
Often that one thing just by itself solves my performance issues.  The
web is such a pig.  It always has been.

It is also possible that a collection of lint over years may have
installed processes on your laptop that you aren't currently needing.
All of those will consume some resources.  For example I have MySQL
and Apache installed on my laptop.  I don't need it all of the time.
I stop it when I am not using it.  You might want to review what is
installed and running and uninstall the lint that you are not needing
anymore.  Or just temporary stop running things (like my use of apache
and mysql) that you are not needing at the moment.  A lean system is a
mean system. :-)

I have no idea if any of that will show anything for you.  But it is
all I have to offer and so offer it regardless.

Good luck!
Bob