[K12OSN] bottleneck question

Les Mikesell les at futuresource.com
Thu Sep 9 04:14:10 UTC 2004

On Wed, 2004-09-08 at 21:46, Liam Marshall wrote:
> >
> >It is the activity more than the amount that will slow you
> >down - loaded but inactive programs that are paged out
> >don't hurt much.  Do a 'vmstat 5' so you see snapshots
> >every 5 seconds and if the 'si' and 'so' numbers show
> >paging activity in normal operation then RAM will help.
> >
> >  
> thanks for the input,  but I just don't  no how to interpret  what you 
> said.  I will check to si and so numbers, but how do I interpret them?

It shows the blocks of memory being swapped out (so) to disk and 
back in (si) in KB/s.   You can tolerate some unused parts of
large programs being swapped out to gain virtual memory space,
but if the memory for active programs is threshing to disk
memory access effectively slows down to disk speed.

You will also see the cpu use and idle time.  If your swap
partition is on an efficient scsi disk you might see the
cpu have a fairly high idle percentage while the system
waits for disk access.  With an IDE system you might see
high cpu use along with swap activity.   If you see high
cpu use (low idle percentage) and little swapping, it
won't help much to add RAM.

   Les Mikesell
    les at futuresource.com

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