Bug 438603 - KVM does not free allocated memory
KVM does not free allocated memory
Product: Fedora
Classification: Fedora
Component: kvm (Show other bugs)
All Linux
low Severity low
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Assigned To: Jeremy Katz
Fedora Extras Quality Assurance
Depends On:
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Reported: 2008-03-22 14:08 EDT by Ralf Ertzinger
Modified: 2008-03-31 11:21 EDT (History)
2 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2008-03-31 11:21:44 EDT
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RHEL 7.3 requirements from Atomic Host:
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Description Ralf Ertzinger 2008-03-22 14:08:12 EDT
Description of problem:
Stopping a kvm-enabled virtual machine does not free the memory allocated to
that machine, the memory is essentially lost until the kernel is rebooted.

Looks like this:
[sun@lain ~/xen/xos :) 38]$ free
             total       used       free     shared    buffers     cached
Mem:       3084812    2362980     721832          0      54752    1417440
-/+ buffers/cache:     890788    2194024
Swap:      1015800          0    1015800
[sun@lain ~/xen/xos :) 40]$ sudo ./start
(this essentially starts qemu-kvm with the necessary parameters, this machine
has 256MB RAM allocated)
config qemu network with bridge for  tap1
[sun@lain ~/xen/xos :( (1) 41]$ free
             total       used       free     shared    buffers     cached
Mem:       3084812    2615736     469076          0      55368    1416820
-/+ buffers/cache:    1143548    1941264
Swap:      1015800          0    1015800

As can be seen, the "used" memory has increased by roughly 256MB.

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. see above
Actual results:
Memory for the virtual machine is never freed

Expected results:
Memory for the virtual machine is freed after machine shutdown

Additional info:
Comment 1 Daniel Berrange 2008-03-23 09:52:03 EDT
Bug in 2.6.25-fc5 kernel, patch on kvm-devel

Comment 2 Jeremy Katz 2008-03-23 21:07:21 EDT
As Dan says, this is being discussed on kvm-devel.  Although apparently that
patch isn't quite enough to fix it.  Once there's a fix in the thread, I'll make
sure it gets into our kernels.
Comment 3 Jeremy Katz 2008-03-31 11:21:44 EDT
Should be fixed with current kernels (we added the patch, then took in the
upstream version)

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