Memory issue

[Matt Domsch]

On Sat, Mar 21, 2009 at 10:26:21PM -0500, Mike McGrath wrote:
> What am I missing here?  This happened on db3 again -
> 
>              total       used       free     shared    buffers     cached
> Mem:      18480632   18383512      97120          0      25968   17305332
> -/+ buffers/cache:    1052212   17428420
> Swap:      3145720    3145720          0
> 
> 
> 1) This box was swapping out like crazy.
> 
> 2) All swap was full
> 
> 3) oomkiller didn't start
> 
> 4) Load went up a little bit, topped out at 3
> 
> 5) no issues with the box at all, has postgres on it, kept running, wasn't
> slow, box was completely responsive.
> 
> 6) It's done this before, and aside from nagios alerting us the swap was
> full, not had any issues with the box.

There are ~30 postgres processes running, many with RSS > 1.6GB, and
nearly all marked idle.  If these processes aren't actively running,
they each can get swapped out to free memory for use by the page
cache. The page cache is consuming 17GB, which it's free to do if no
applications are actually _running_ that need more memory.  The
processes that are running and touching the database will cause those
disk accesses to get cached in the page cache.

-- 
Matt Domsch
Linux Technology Strategist, Dell Office of the CTO
linux.dell.com & www.dell.com/linux