[nycbug-talk] Memory sizing

[Marc Spitzer]

On 4/22/06, Francisco Reyes <lists at stringsutils.com> wrote:
> Charles Sprickman writes:
>
> > Another resource (besides this fine list) is the Postgresql-performance
> > list.
>
> I am familiar with that list. I am subscribed to it.
> However I am trying to learn from the FreeBSD side first.. how to read
> the memory portion of "top" and whatever other tool there is to figure
> memory status.

here is a nice explanation of the memory description, from tops man page:



DESCRIPTION OF MEMORY
       Mem:  9220K  Active, 1032K Inact, 3284K Wired, 1MB Cache, 2M Buf, 1320K
       Free Swap:   91M Total, 79M Free, 13% Inuse, 80K In, 104 K Out

       K: Kilobyte

       M:     Megabyte

       %:     1/100

       Active:
              number of pages active

       Inact: number of pages inactive

       Wired: number of pages wired down, including cached file data pages

       Cache: number of pages used for VM-level disk caching

       Buf:   number of pages used for BIO-level disk caching

       Free:  number of pages free

       Total: total available swap usage

       Free:  total free swap usage

       Inuse: swap usage

       In:    pages paged in from swap devices (last interval)

       Out:   pages paged out to swap devices (last interval)

what needs more explanation, other then Wired which I am not too sure
about?  pstat, vmstat and things pointed to in their man pages might
also be of interest also look at thing that end in stat, some may be
useful:

[marc at laptop ~]$ ls {/sbin/,/bin/,/usr/bin/,/usr/sbin/}*stat
ls: /bin/*stat: No such file or directory
/sbin/ipfstat           /usr/bin/stat           /usr/sbin/iostat
/sbin/kldstat           /usr/bin/systat         /usr/sbin/pmcstat
/usr/bin/btsockstat     /usr/bin/uustat         /usr/sbin/pstat
/usr/bin/fstat          /usr/bin/vmstat         /usr/sbin/purgestat
/usr/bin/netstat        /usr/sbin/gstat         /usr/sbin/slstat
/usr/bin/nfsstat        /usr/sbin/hoststat
/usr/bin/sockstat       /usr/sbin/ifmcstat
[marc at laptop ~]$

and some will not, slstat for examle.

Also put a $value on an hour of your time.  so you do not spend $1000
on researching a $200 question.  I just looked at pricewatch.com and
memory is cheap enough that you should just buy lots and be done, 2gb
stick is running around $140-175.

>
> Only one of the two machines I will be ordering soon will be a DB server.

this is definatly a $200 question, assuming there are 4 slots
available just get 2 of the bigest sticks that fit and buy 2 more if
it is not big enough. Or just fill it with the argument is it worth X
to run the risk of memory being a problem.

marc

--
"We trained very hard, but it seemed that every time we were beginning to
form into teams we would be reorganized. I was to learn later in life that
we tend to meet any new situation by reorganizing, and a wonderful method it
can be for creating the illusion of progress, while producing confusion,
inefficiency and demoralization."
-Gaius Petronius, 1st Century AD