Bob Proulx bob at proulx.com
Fri Mar 16 11:26:06 MDT 2012

Kerry Miller wrote:
> This is the information from $ free.

Looks like you have 2 gig of memory plus 2 gig of swap configured.  A
small amount of swap has been used which is typical in that size range
and doesn't indicate anything unusual by itself.

It looks like there is a large amount of free space.  That is unusual.
The Linux kernel is designed to put memory to work for you.  Any free
memory is usually quickly used as buffer cache.  This leads me to
believe there was a large memory application running that just exited
in the recent machine time before that snapshot.  Speculating that a
large running application squeezed out the buffer cache and caused
some unused pages to be pushed to swap and then subsequently exited.
That is a typical reason that there will be both a large amount of
free space coupled with having some pages in used swap space.

I might also speculate that Firefox is the most typical memory pig
that is often run by users.  Firefox hitting Gmail and Facebook or
other image and Javascript heavy sites can consume an inordinate
amount of memory.  I single out Firefox being a typical offender but
really all of the browsers have problems being light when the site is
designed to use a lot of resources.  Then if the browser is exited all
of that memory is freed all at once.

Another typical large memory application is OpenOffice.org /
LibreOffice running on a large office file.  It might need to consume
a lot of memory rendering images and fonts and other things.  Then
again when exited the memory is freed.

Sorry, no answers.  Another question for looking at swap rate usage
and swapping.  Run 'vmstat' in a terminal window and look at the swap
in (si) and swap out (so) rates.

  $ vmstat
  procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
   r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
   3  0  18200  16544  28460  43640    0    0    22     9  187  149  1  1 97  1

Numbers of 0 or 1 are okay.  But if you saw a large rate of say 10 or
20 then that would indicate to me that it is swapping.


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