Bug 435208

Summary: Guest Memory can not be updated after upgrade to kernel-xen-2.6.18-53.1.13.el5
Product: Red Hat Enterprise Linux 5 Reporter: Daniel D <dd.zinc>
Component: kernel-xenAssignee: Xen Maintainance List <xen-maint>
Status: CLOSED NOTABUG QA Contact: Martin Jenner <mjenner>
Severity: medium Docs Contact:
Priority: low    
Version: 5.1   
Target Milestone: rc   
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2008-02-27 23:14:46 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description Daniel D 2008-02-27 22:38:20 UTC 
From Bugzilla Helper:
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Description of problem:
using "xm mem-set" command to increase memeory for a guest system, gives not the expected result.

This was working with previous kernel: kernel-xen-2.6.18-53.1.6.el5


Version-Release number of selected component (if applicable):
kernel-xen-2.6.18-53.1.13.el5

How reproducible:
Always


Steps to Reproduce:
1. xm list 
Name                                      ID Mem(MiB) VCPUs State   Time(s)
Domain-0                                   0     7034     8 r-----    111.4
aaa                                        1     1024     2 -b----     15.2

2. xm mem-set aaa 2000
3. xm list
Name                                      ID Mem(MiB) VCPUs State   Time(s)
Domain-0                                   0     7034     8 r-----    113.4
aaa                                        1     1024     2 -b----     15.3

4. xm list
Name                                      ID Mem(MiB) VCPUs State   Time(s)
Domain-0                                   0     7034     8 r-----    114.6
aaa                                        1      499     2 -b----     15.8

5. xm mem-set aaa 2000
6. xm list
Name                                      ID Mem(MiB) VCPUs State   Time(s)
Domain-0                                   0     7034     8 r-----    116.6
aaa                                        1     1024     2 -b----     16.1



Actual Results:
Memory for guest "aaa" cannot be increased more than 1024MB, even if in config there is  maxmem=3000 (see additional info). Allocate less the initial memory works fine.

Expected Results:
Increase memory allocated to guest as specified on command line (xm mem-set aaa 2000) for 2000MB

Additional info:
Guest config file:

[root@host ~]# vi /etc/xen/aaa
name = "aaa"
uuid = "e957cacf-d644-c366-9eb9-a5670c5341e2"
maxmem = 3024
memory = 1024
vcpus = 2
bootloader = "/usr/bin/pygrub"
on_poweroff = "destroy"
on_reboot = "restart"
on_crash = "restart"
vfb = [ "type=vnc,vncunused=1" ]
disk = [ "tap:aio:/opt/xen-tests/aaa/root.img,xvda,w" ]
vif = [ "mac=00:16:3e:xx:xx:yy,bridge=xenbr1", "mac=00:16:3e:xx:xx:xx,bridge=xenbr0" ]

(I replaced the actual Mac addresses with xx and yy)
Comment 1 Chris Lalancette 2008-02-27 22:48:56 UTC 
Hm, I'm assuming there is 8GB of memory in the machine?  If that is the case,
what you are doing won't actually work.  You need to do:

xm mem-set 0 6000
xm mem-set aaa 2000

That is, the mem-set command does not automatically balloon down dom0 to make
room for the new memory.  Can you try that out and see if it works?

Chris Lalancette
Comment 2 Daniel D 2008-02-27 23:06:29 UTC 
Yes, it works if I reduce Domain0 memory first. On another machine with older
kernel there has been already reduced domain0 before, so it was my
misunderstanding, sorry!

Thanks for help
Comment 3 Chris Lalancette 2008-02-27 23:14:46 UTC 
No problem, it is a common thing.

Closing out.

Chris Lalancette