I got a newly built RedHat Linux server box (Enterprise ES release 2.1)
with 4G RAM. Checking memory with free command shows about 2.7G is being
used (see the output below):

total used free shared buffers cached
Mem: 3863200 2757620 1105580 0 532672 2079748
-/+ buffers/cache: 145200 3718000
Swap: 2048276 4888 2043388

I don't understand why that large amount of RAM is consumed without an
application running yet. Is it a configuration issue, or OS just needs
that much memory? Maybe I misunderstand something, but your
clarification is appreicated.

Thanks


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On 2004-08-26, John <jchen@gov.mb.ca> wrote:
> I don't understand why that large amount of RAM is consumed without an

This ain't Windows.
memory unused=memory wasted. The system use always all the available
memory for caching and buffering, when an application require it, the
Os will release the memory and allocate it to the program and get it
back when the application is terminated.

Davide

--
If anything can go wrong, it will.

John wrote:

> I got a newly built RedHat Linux server box (Enterprise ES release 2.1)
> with 4G RAM. Checking memory with free command shows about 2.7G is being
> used (see the output below):
>
> total used free shared buffers cached
> Mem: 3863200 2757620 1105580 0 532672 2079748
> -/+ buffers/cache: 145200 3718000
> Swap: 2048276 4888 2043388
>
> I don't understand why that large amount of RAM is consumed without an
> application running yet.

1. What services do you have configured? Do you have sendmail, httpd, etc.?
These require a lot of memory just in order to idle.

2. The actual, available memory may not be reflected in the output listed.
Some memory is available but not reclaimed until it is needed.

--
Paul Lutus
http://www.arachnoid.com

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In comp.os.linux.setup John <jchen@gov.mb.ca> suggested:
> I got a newly built RedHat Linux server box (Enterprise ES release 2.1)
> with 4G RAM. Checking memory with free command shows about 2.7G is being
> used (see the output below):

> total used free shared buffers cached
> Mem: 3863200 2757620 1105580 0 532672 2079748
> -/+ buffers/cache: 145200 3718000
^^^^^^^^^^^^^^^^^
> Swap: 2048276 4888 2043388

No it isn't used, only 145 MB are really used, the rest is used
as (disk) cache/buffers and will be used for other things as soon
as it is needed.

[..]

--
Michael Heiming (GPG-Key ID: 0xEDD27B94)
mail: echo zvpunry@urvzvat.qr | perl -pe 'y/a-z/n-za-m/'
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On Thu, 26 Aug 2004 19:23:54 -0000, Michael Heiming wrote:
[..]
>> total used free shared buffers cached
>> Mem: 3863200 2757620 1105580 0 532672 2079748
>> -/+ buffers/cache: 145200 3718000
> ^^^^^^^^^^^^^^^^^
>> Swap: 2048276 4888 2043388
>
> No it isn't used, only 145 MB are really used, the rest is used
> as (disk) cache/buffers and will be used for other things as soon
> as it is needed.

Curious. Why would something be swapping?

Rinaldi
--
Some people in this department wouldn't recognize subtlety if it hit
them on the head.

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In comp.os.linux.setup Rinaldi J. Montessi <rinaldi@senior.envision> suggested:
> On Thu, 26 Aug 2004 19:23:54 -0000, Michael Heiming wrote:
> [..]
>>> total used free shared buffers cached
>>> Mem: 3863200 2757620 1105580 0 532672 2079748
>>> -/+ buffers/cache: 145200 3718000
>> ^^^^^^^^^^^^^^^^^
>>> Swap: 2048276 4888 2043388
>>
>> No it isn't used, only 145 MB are really used, the rest is used
>> as (disk) cache/buffers and will be used for other things as soon
>> as it is needed.

> Curious. Why would something be swapping?

Something like running updatedb might be the reason or VM just
likes to take a small taste of swap for measuring performance or
whatever reason, you'll probably find the answer right in the
kernel sources.

--
Michael Heiming (GPG-Key ID: 0xEDD27B94)
mail: echo zvpunry@urvzvat.qr | perl -pe 'y/a-z/n-za-m/'
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Thanks to all for quick response, and particularly to Michael.
Your explanation does shed some light on my mind.
Do you also know the meaning of used mem, and how it is counted?
I really want to find out the relationships among those reported items.
I checked man page and other info available to me, but it's still a
puzzle to me. Maybe I am a bit greedy.


"John" <jchen@gov.mb.ca> wrote in message
news:7392ddaead9e8f467a66184e89763358.31434@mygate .mailgate.org

> I got a newly built RedHat Linux server box (Enterprise ES release 2.1)
> with 4G RAM. Checking memory with free command shows about 2.7G is being
> used (see the output below):
>
> total used free shared buffers cached
> Mem: 3863200 2757620 1105580 0 532672 2079748
> -/+ buffers/cache: 145200 3718000
> Swap: 2048276 4888 2043388
>
> I don't understand why that large amount of RAM is consumed without an
> application running yet. Is it a configuration issue, or OS just needs
> that much memory? Maybe I misunderstand something, but your
> clarification is appreicated.
>
> Thanks




--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

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In comp.os.linux.setup John <jchen@gov.mb.ca> suggested:

[..]

> Do you also know the meaning of used mem, and how it is counted?

Used mem is simply including shared, buffers and cached memory.
'free' simply looks in /proc/meminfo, try 'cat /proc/meminfo'.

> I really want to find out the relationships among those reported items.
> I checked man page and other info available to me, but it's still a
> puzzle to me. Maybe I am a bit greedy.

There are a bunch of tools available most come with the procps
package, 'top' might be interesting and 'man proc' in addition.

Good luck

--
Michael Heiming (GPG-Key ID: 0xEDD27B94)
mail: echo zvpunry@urvzvat.qr | perl -pe 'y/a-z/n-za-m/'
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Rinaldi J. Montessi wrote:
> On Thu, 26 Aug 2004 19:23:54 -0000, Michael Heiming wrote:
> [..]
>
>>> total used free shared buffers cached
>>>Mem: 3863200 2757620 1105580 0 532672 2079748
>>>-/+ buffers/cache: 145200 3718000
>>
>> ^^^^^^^^^^^^^^^^^
>>
>>>Swap: 2048276 4888 2043388
>>
>>No it isn't used, only 145 MB are really used, the rest is used
>>as (disk) cache/buffers and will be used for other things as soon
>>as it is needed.
>
>
> Curious. Why would something be swapping?
>
> Rinaldi

¿Why it should be in memory when you don't need it? Linux surely
thinks it's better to use the real memory for caching the disk.
In the Linux manuals says Linux works better if you have swap
memory, even if you have plenty of memory.

--

Jose Maria Lopez Hernandez
Director Tecnico de bgSEC
jkerouac@bgsec.com
bgSEC Seguridad y Consultoria de Sistemas Informaticos
http://www.bgsec.com
ESPAÑA

The only people for me are the mad ones -- the ones who are mad to live,
mad to talk, mad to be saved, desirous of everything at the same time,
the ones who never yawn or say a commonplace thing, but burn, burn, burn
like fabulous yellow Roman candles.
-- Jack Kerouac, "On the Road"

"Jose Maria Lopez Hernandez" <jkerouac@bgsec.com> wrote in message
news:SktXc.110485$r4.2814278@news-reader.eresmas.com...
> Rinaldi J. Montessi wrote:
> > On Thu, 26 Aug 2004 19:23:54 -0000, Michael Heiming wrote:
> > [..]
> >
> >>> total used free shared buffers cached
> >>>Mem: 3863200 2757620 1105580 0 532672 2079748
> >>>-/+ buffers/cache: 145200 3718000
> >>
> >> ^^^^^^^^^^^^^^^^^
> >>
> >>>Swap: 2048276 4888 2043388
> >>
> >>No it isn't used, only 145 MB are really used, the rest is used
> >>as (disk) cache/buffers and will be used for other things as soon
> >>as it is needed.
> >
> >
> > Curious. Why would something be swapping?
> >
> > Rinaldi
>
> ¿Why it should be in memory when you don't need it? Linux surely
> thinks it's better to use the real memory for caching the disk.
> In the Linux manuals says Linux works better if you have swap
> memory, even if you have plenty of memory.

Disk caching. Why not leave the last N megabytes of disk accessed in the
cache if you're not otherwise using it, to reduce the latency of disk
requests?