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Linux - Virtualization and Cloud This forum is for the discussion of all topics relating to Linux Virtualization and Linux Cloud platforms. Xen, KVM, OpenVZ, VirtualBox, VMware, Linux-VServer and all other Linux Virtualization platforms are welcome. OpenStack, CloudStack, ownCloud, Cloud Foundry, Eucalyptus, Nimbus, OpenNebula and all other Linux Cloud platforms are welcome. Note that questions relating solely to non-Linux OS's should be asked in the General forum.

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Old 03-29-2011, 09:46 AM   #1
nayabingi
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Registered: Jul 2004
Location: Atlanta , United States
Distribution: CentOS 5
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Guest Kernel Reserved Memory Very High


Hi all,

I have a 64bit CentOS 5.5 Base VM running on Xen-3.4.2-2.el5. The memory usage seams very high for a idle system. After looking into why I found that the kernel was reserving about 300MB of RAM at boot time. This seams like a large amount and I believe the kernel will not release this RAM that it reserved. Can some tell me why such large amount?

[root@xxxxx ~]# dmesg | grep Memory
Memory: 691316k/16785408k available (2513k kernel code, 356548k reserved, 1399k data, 184k init)

[root@xxxxx ~]# free -m
total used free shared buffers cached
Mem: 1024 581 442 0 34 137
-/+ buffers/cache: 409 614
Swap: 1023 0 1023

Thank you
 
Old 04-14-2011, 11:55 AM   #2
unSpawn
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Understanding the Linux Virtual Memory Manager

Linux (the kernel) has a well-performing VMM (virtual memory manager) so unless you use some exotic setup any sysctl values with respect to memory handling do not need tweaking or otherwise dealing with: just let the kernel handle things. Also see Mel Gorman's book "Understanding the Linux Virtual Memory Manager" here: http://www.kernel.org/doc/gorman/.


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