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Re: [Xen-users] domUs high memory usage (FC5 -- Xen 3.0.2)

To: dgreen@xxxxxxxxxxx
Subject: Re: [Xen-users] domUs high memory usage (FC5 -- Xen 3.0.2)
From: Hans de Hartog <dehartog@xxxxxxxxxx>
Date: Sun, 03 Sep 2006 20:54:52 +0200
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Hi Vince,

Yes, I think it is normal. If your system runs for a day,
think of all the things that happen: your cronjobs (hourly,
daily), cron itself, all the kernel helper daemons and
things like sshd, ntpd, journaling, and so on).
Look at ps -ef and see what is running. From all those
things, the last used are still in memory and stay there
until something else needs memory.
Please let somebody correct me if I'm wrong but if a unix
system has a lot of free memory, then
 - it just booted, or
 - has too much memory, or
 - memory allocation is not optimal (IMHO)


dgreen@xxxxxxxxxxx wrote:
> Thanks for your response Hans.
> I have only used the ping command and nothing more.  Are there other
> services in the background that are starting and grabbing this memory?  I
> have used Solaris, FC5, SuSE without Xen and never noticed this hogging of
> all the memory for such a period of time.  So, you're saying that each
> time I do a top on a VM I will see 'Mem: 262284k total, 256996k used' and
> that this is normal?
> Vince
>>>I start up my domU's (in a console) and they seem to run at ~75MB (out
>>>256MB) of memory.  The only thing I have done on the VMs is to use ping
>>>test RTT's.  I come back to the VM's the next day and notice that all of
>>>them are running ~256MB.  I haven't started any other services.
>>Hello Vince,
>>That's a unix filosofy: free memory is a waiste. Therefore, whatever
>>the memory is used for (buffers, cache, programs) is not freed if
>>not necessary to do other things. So eventually most of the memory
>>is in use because if you need something you used before, it is faster
>>if it is still in memory than to read it from disk again.

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