[SWLUG] how much more CPU performance can one get these days?

[Justin Mitchell]

On Fri, 2009-09-18 at 11:10 +0100, Mark Summerfield wrote:

> > also make sure that the process isnt starved for memory, use something
> > like vmstat to make sure theres no significant swapping happening, as
> > that would be a slowdown and easily fixed with more ram.
> 
> I get (meaningless to me):
> 
> : vmstat
> procs -----------memory---------- ---swap-- -----io---- --system-- -----
> cpu------
>  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id 
> wa st
>  1  0 296960 1093356  13792 223880   14   21   198   184  635  611 23  4 68  
> 4  0	

do something like 'vmstat 5' which will print the line once every 5
seconds, and watch how the numbers go for a while.

of interest in this case is :-

si - blocks swapped into ram
so - blocks swapped out to disk

bi - disk blocks read
bo - disk blocks written

if si and so are regularly non-zero then the system is having to swap
things between ram and disk to satisfy all the memory requirements of
whats running, try and eliminate any memory hungry programs, or go buy
more ram.  

small amounts of swapping on a system are generally harmless, but if its
your number crunching program thats having to be swapped all the time
then its going to be taking a massive performance penalty.