Re: Low values for cached size

[Carlos Henrique Reimer <carlos.reimer@xxxxxxxxxxxxx>]

Hi Scott,

 

The top and M option:

 

top - 20:37:52 up  8:19,  2 users,  load average: 0.00, 0.00, 0.00
Tasks:  96 total,   1 running,  95 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.0%us,  0.2%sy,  0.0%ni, 99.5%id,  0.3%wa,  0.0%hi,  0.0%si,  0.0%st
  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 4011 postgres  18   0  298m 276m 251m S    0  7.8   0:40.16 postgres
 2950 postgres  15   0  271m 232m 231m S    0  6.6   0:01.06 postgres
 2938 postgres  18   0  271m 7120 6748 S    0  0.2   0:00.31 postgres
 3012 root      18   0 10852 5644 1588 S    0  0.2   0:00.01 miniserv.pl
 2660 root      15   0 13448 4616  968 S    0  0.1   0:00.01 python
 2732 ntp       15   0  4316 4316 3312 S    0  0.1   0:00.04 ntpd
 2397 root      12  -3 10100 3860 2272 S    0  0.1   0:00.08 python
 2870 haldaemo  18   0  5700 3724 1608 S    0  0.1   0:01.51 hald
 5917 root      18   0 10424 2804 1388 S    0  0.1   0:00.00 httpd
 5992 root      15   0  9000 2724 2204 S    0  0.1   0:00.03 sshd
 5140 root      16   0  8996 2720 2204 S    0  0.1   0:00.04 sshd
 5918 apache    23   0 10424 2084  632 S    0  0.1   0:00.00 httpd
 5920 apache    23   0 10424 2084  632 S    0  0.1   0:00.00 httpd
 5921 apache    23   0 10424 2084  632 S    0  0.1   0:00.00 httpd
 5922 apache    23   0 10424 2084  632 S    0  0.1   0:00.00 httpd
 5923 apache    25   0 10424 2084  632 S    0  0.1   0:00.00 httpd
 5924 apache    25   0 10424 2084  632 S    0  0.1   0:00.00 httpd
 5925 apache    25   0 10424 2084  632 S    0  0.1   0:00.00 httpd
 5926 apache    25   0 10424 2084  632 S    0  0.1   0:00.00 httpd
 2696 root      18   0  9676 1968 1360 S    0  0.1   0:00.00 cupsd
 2757 root      15   0  9028 1860  776 S    0  0.1   0:00.00

 

Thank you!

 

sendmail2009/9/25 Scott Marlowe <scott.marlowe@xxxxxxxxx>

On Fri, Sep 25, 2009 at 3:28 PM, Carlos Henrique Reimer
<carlos.reimer@xxxxxxxxxxxxx> wrote:
> Hi,
>
> We're facing performance problems in a Linux box running CentOS release 5
> (Final) and PostgreSQL 8.2.4. I've done some basic checks in the
> configuration but everything looks fine to me. One weird behaviour I've
> found is the cached size showed by the
> "top" and "free" Linux commands:
>
> top - 08:32:17 up 3 days, 19:04,  1 user,  load average: 1.09, 1.07, 1.10
> Tasks: 173 total,   2 running, 170 sleeping,   0 stopped,   1 zombie
> Cpu(s):  9.5%us,  0.5%sy,  0.0%ni, 88.2%id,  1.7%wa,  0.0%hi,  0.0%si,
> 0.0%st
> Mem:   3631900k total,  3378056k used,   253844k free,    25488k buffers
> Swap:  4192956k total,      100k used,  4192856k free,  2356588k cached
>
> [postgres@server01 etc]$ free
>              total       used       free     shared    buffers     cached
> Mem:       3631900    3174804     457096          0      14280    2086184
> -/+ buffers/cache:    1074340    2557560
> Swap:      4192956        108    4192848
> [postgres@server01 etc]$
>
> Both commands show values ranging from 2GB to 2.3GB for the cached size and
> the server has 3.5GB RAM. I do usally see  cached values with sizes bearing
> the size of the RAM in other servers. It seams that something is consuming
> the RAM and not letting it free to be used as cache for Linux files, right?
> The shared_buffers (256MB) is not high and I can not see a reason for this.
> Initially I've thought the problem was
> because the system was running with runlevel 5, but now, it's running with
> runlevel 3 and even so the values for
> cached size does not change.
>
> Any suggestions or directions I could follow to discover the reason?

If you run top, then hit M, and post the first 20 or so rows after
what you have here I can take a guess.

-- 
Reimer
47-3457-0881 47-9183-0547 msn: carlosreimer@xxxxxxxxxxx
skype: carlosreimer