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Re: Memory problems



On 06/02/2010 09:06 AM, Jonatan Soto wrote:
Hi list,

I'm facing a problem with lenny regarding to memory usage.

I have 4 VM lenny based on top of a VMWare ESXi. The system is running for a few days and top command shows a very high amount of memory consumption for each server. I have a little knowledge of how linux (kernel 2.6) manages memory. A nice resource I found is this:
http://www.linuxhowtos.org/System/Linux%20Memory%20Management.htm

So, I understand that cached memory may be free if some application requires it but I don't understand why lenny is consuming 2GB of physical memory. It's worth to mention that all the systems are running with only the standard package installed and few additional daemons for each server.

I post what top command shows in order to provide better clues of what's going on:

Server1:
top - 18:47:12 up 12 days, 3:57, 2 users, load average: 0.00, 0.00, 0.00
Tasks:  53 total,   2 running,  51 sleeping,   0 stopped,   0 zombie
Mem:   3097764k total,  2901684k used,   196080k free,   156460k buffers
Swap:   578300k total,        0k used,   578300k free,   592736k cached
additional daemons -> apache2, bind9, sshd

Server2:
top - 18:48:30 up 12 days, 2:29, 2 users, load average: 0.00, 0.00, 0.00
Tasks:  55 total,   1 running,  54 sleeping,   0 stopped,   0 zombie
Mem:   3097764k total,  2412008k used,   685756k free,   145204k buffers
Swap:   915664k total,        0k used,   915664k free,   155112k cached
additional daemons -> apache2, sshd

Server3:
top - 18:52:10 up 12 days, 2:32, 2 users, load average: 0.00, 0.00, 0.00
Tasks:  72 total,   1 running,  71 sleeping,   0 stopped,   0 zombie
Mem:   3097764k total,  2263200k used,   834564k free,    49152k buffers
Swap:  2928632k total,        0k used,  2928632k free,   107700k cached
additional daemons -> lvm, sshd

Server4:
top - 16:50:19 up 1 day,  6:42,  2 users,  load average: 0.00, 0.00, 0.00
Tasks:  58 total,   1 running,  57 sleeping,   0 stopped,   0 zombie
Mem:   3097764k total,   272300k used,  2825464k free,   126164k buffers
Swap:  1341388k total,        0k used,  1341388k free,    53196k cached
additional daemons -> bind9, sldap, samba, sshd

--------------------
I like to think of the drive cache as the computer saying "We'll hold onto this information you read from the hard drive in memory just in case you want to use again soon. The memory wouldn't be doing anything if empty anyways." Essentially I count cache as free memory because the OS will drop it in a heartbeat if an application needs it.

Also, it is reasonable that the cache increases as the uptime does because the computer reads more from the hard drive that can be cached as time goes on.

Brian Oborn


Note that I've recently rebooted Server4 and it has lower memory consumption rather than the others and it is running more daemons. May be this issue is a misconfiguration of my servers or a memory leak? Should I tweak something in order to improve memory management?

Any help would be much appreciated.

PD: Apache2 is installed using default configuration of the Apache2 official Debian release.







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