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Old 11-12-2011, 02:07 PM
"John J. Boyer"
 
Default Trouble with Mailman

I have set up Mailman on a virtual private server from 1and1 running
Centos, though I can't tell which version. The system has 2 GB of
memory. Mailman is receiving posts, but it is not sending them out to
everybody. It is also getting some out-of-memory errors. The server is
also runing Plesk for Web hosting. Something on the server is leaking
memory. When first booted it has nearly 1.5 GB of free memory. Now this
is down to .75 GB. Any hints will be appreciated.

Thanks,
--
John J. Boyer; President, Chief Software Developer
Abilitiessoft, Inc.
http://www.abilitiessoft.com
Madison, Wisconsin USA
Developing software for people with disabilities

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Old 11-12-2011, 02:45 PM
Johnny Hughes
 
Default Trouble with Mailman

On 11/12/2011 09:07 AM, John J. Boyer wrote:
> I have set up Mailman on a virtual private server from 1and1 running
> Centos, though I can't tell which version. The system has 2 GB of
> memory. Mailman is receiving posts, but it is not sending them out to
> everybody. It is also getting some out-of-memory errors. The server is
> also runing Plesk for Web hosting. Something on the server is leaking
> memory. When first booted it has nearly 1.5 GB of free memory. Now this
> is down to .75 GB. Any hints will be appreciated.
>

Linux puts things in cache using extra (unused) memory. It is
absolutely normal to have "Free Memory" go down to a fairly small level
and have Buffers and Cache grow.

If you are getting out of memory errors, you can tweek the amount of
memory that they system keeps in reserve using "vm.min_free_kbytes" in
/etc/sysctl.conf

http://lists.centos.org/pipermail/centos/2006-December/030761.html

This is a good article that discusses how to adjust this too:

http://www.dba-oracle.com/t_tuning_linux_kernel_2_6_oracle.htm

As far as what version of CentOS you have ... you can figure that out with:

cat /etc/redhat-release


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Old 11-13-2011, 12:32 PM
"John J. Boyer"
 
Default Trouble with Mailman

On Sat, Nov 12, 2011 at 09:45:04AM -0600, Johnny Hughes wrote:

> Linux puts things in cache using extra (unused) memory. It is
> absolutely normal to have "Free Memory" go down to a fairly small level
> and have Buffers and Cache grow.
Why does Linux do this? It seems odd to me.

>
> If you are getting out of memory errors, you can tweek the amount of
> memory that they system keeps in reserve using "vm.min_free_kbytes" in
> /etc/sysctl.conf
I don't find vm.min_free_byes in sysctl.conf. It isn't mentioned in the
man pages.

Thanks.
John

>
> http://lists.centos.org/pipermail/centos/2006-December/030761.html
>
> This is a good article that discusses how to adjust this too:
>
> http://www.dba-oracle.com/t_tuning_linux_kernel_2_6_oracle.htm
>
> As far as what version of CentOS you have ... you can figure that out with:
>
> cat /etc/redhat-release
>
>



> _______________________________________________
> CentOS mailing list
> CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos


--
John J. Boyer; President, Chief Software Developer
Abilitiessoft, Inc.
http://www.abilitiessoft.com
Madison, Wisconsin USA
Developing software for people with disabilities

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http://lists.centos.org/mailman/listinfo/centos
 
Old 11-13-2011, 03:11 PM
Benjamin Franz
 
Default Trouble with Mailman

On 11/13/2011 05:32 AM, John J. Boyer wrote:
> On Sat, Nov 12, 2011 at 09:45:04AM -0600, Johnny Hughes wrote:
>
>> Linux puts things in cache using extra (unused) memory. It is
>> absolutely normal to have "Free Memory" go down to a fairly small level
>> and have Buffers and Cache grow.
> Why does Linux do this? It seems odd to me.

Because it means that once you've accessed something once, accessing it
a second time is orders of magnitude faster. Memory that is not being
used at all is a waste of resources. It dramatically improves the
performance of a system to use otherwise unused memory for caching and
buffers.

--
Benjamin Franz
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Old 11-13-2011, 03:15 PM
Reindl Harald
 
Default Trouble with Mailman

Am 13.11.2011 14:32, schrieb John J. Boyer:
> On Sat, Nov 12, 2011 at 09:45:04AM -0600, Johnny Hughes wrote:
>
>> Linux puts things in cache using extra (unused) memory. It is
>> absolutely normal to have "Free Memory" go down to a fairly small level
>> and have Buffers and Cache grow

> Why does Linux do this? It seems odd to me

because taht is why linux is in some cases thousand times faster
as reading the same things over and over from the disk and why
would you install many GB memory if it is unused

target of a modern operating system is using 16 GB of 16 GB memory
after some time and if any application requests actively
memory the oldest caches/buffers are reclaimed to the app

[harry@srv-rhsoft:~]$ uptime
17:14:54 up 3:54, 6 users, load average: 0.00, 0.04, 0.12

[harry@srv-rhsoft:~]$ free -m
total used free shared buffers cached
Mem: 16035 15366 668 0 118 12951
-/+ buffers/cache: 2296 13738
Swap: 2047 0 2047


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Old 11-13-2011, 07:59 PM
John R Pierce
 
Default Trouble with Mailman

On 11/13/11 8:15 AM, Reindl Harald wrote:
> [harry@srv-rhsoft:~]$ free -m
> total used free shared buffers cached
> Mem: 16035 15366 668 0 118 12951
> -/+ buffers/cache: 2296 13738
> Swap: 2047 0 2047

to better explain that output... the numbers you really want to look
at are the -/+ buffers/caches lines...

At the moment of that output, this machine had 2.2GB used, and 13.7GB
free out of 16GB total. 12.9GB is currently holding cached files, but
those pages can be reused instantly, they are all available for reuse.


--
john r pierce N 37, W 122
santa cruz ca mid-left coast

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Old 11-13-2011, 09:40 PM
Ljubomir Ljubojevic
 
Default Trouble with Mailman

Vreme: 11/13/2011 02:32 PM, John J. Boyer piše:
>> Linux puts things in cache using extra (unused) memory. It is
>> > absolutely normal to have "Free Memory" go down to a fairly small level
>> > and have Buffers and Cache grow.
> Why does Linux do this? It seems odd to me.
>

It is rational usage of available resources. If you utilize available
memory for caching purposes you speed up all services and reduce hard
disk usage, so hard disk lasts longer and all services/programs/daemons
are more snappier (higher performance).

--

Ljubomir Ljubojevic
(Love is in the Air)
PL Computers
Serbia, Europe

Google is the Mother, Google is the Father, and traceroute is your
trusty Spiderman...
StarOS, Mikrotik and CentOS/RHEL/Linux consultant
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Old 11-13-2011, 10:37 PM
Yves Bellefeuille
 
Default Trouble with Mailman

On Sunday 13 November 2011 08:32, John J. Boyer wrote:

> Why does Linux do this? It seems odd to me.

Suppose you have 4 Gb of RAM, of which only 1 Gb is used. What good is
the other 3 Gb doing you? You might as well not have it at all.

Instead of leaving the RAM unused, Linux uses it as a cache. It can't
hurt, and it can help. If a programme needs the memory, Linux will make
it available to the programme quickly enough.

"free" gives me the following report:

$ free
total used free shared buffers cached
Mem: 4147456 3991600 155856 0 98556 2739992
-/+ buffers/cache: 1153052 2994404
Swap: 3911788 248 3911540

Therefore, I have 4 Gb of RAM, of which about 1 Gb is used for the
programmes and a little under 3 Gb is used as a cache.

Apparently Windows finally decided to use a similar approach, which it
calls SuperFetch.

I'm not sure how to disable the cache entirely, but to clear it, with
kernel 2.6.16 or later, do the following as root:

sync ; echo 3 > /proc/sys/vm/drop_caches

--
Yves Bellefeuille <yan@storm.ca>
"La Esperanta Civito ne rifuzas anticipe la kunlaboron de erarintoj, se
ili konscias pri sia eraro." -- Heroldo Komunikas, n-ro 473.
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Old 11-13-2011, 10:44 PM
John R Pierce
 
Default Trouble with Mailman

On 11/13/11 3:37 PM, Yves Bellefeuille wrote:
> Apparently Windows finally decided to use a similar approach, which it
> calls SuperFetch.

windows has been doing this since NT 3.1 circa 1993. superfetch is
something completely different.





--
john r pierce N 37, W 122
santa cruz ca mid-left coast

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