Re: [Xen-users] dynamic memory extension not working on Debian Squeeze

[Peter Viskup <skupko.sk@xxxxxxxxx>]

On 11/14/2012 07:29 PM, Alexandre Kouznetsov wrote:
> Hello, Ian.
>
> I have been living with the same problem for years. I guess it worked 
> on Etch with kernel 2.6.18, not sure about Lenny and 2.6.26. In my 
> case, xenstore works fine.
> The symptom is: after using mem-set, it apparently works, but the DomU 
> still thinks it has the old memory size. The issue shows up only when 
> increasing memory above the original size, the reduction work fine.
> I have read the rest of the thread, and it seems Peter is stuck in 
> some xenstore issue. I suspect xenstore might be unrelated: in my case 
> it works fine, but mem-set still have the issue.
> The OS on Dom0 and DomU is a regular Debian Squeeze, no backports or 
> custom build packages. It has been seen on different models of Dell 
> PowerEdge servers. If relevant, I can confirm for a commodity hardware 
> case, or for a Debian Wheezy case (upgraded from Squeeze, not a clean 
> install). I have no other OS at hand than Debian to test.
> The output of "xenstore-ls -fp" that you asked remains unchanged, so I 
> will post it only once:
> root@on05:~# xenstore-ls -fp | grep scoutapi-dev
> /vm/8b7714b8-eeb0-2120-cee7-59273be76f79/name = "scoutapi-dev"   (n0)
> /local/domain/0/backend/vbd/12/51715/domain = "scoutapi-dev"   (n0,r12)
> /local/domain/0/backend/vbd/12/51715/params = 
> "/dev/r5VG/scoutapi-dev-srv"   (n0,r12)
> /local/domain/0/backend/vbd/12/51714/domain = "scoutapi-dev"   (n0,r12)
> /local/domain/0/backend/vbd/12/51714/params = 
> "/dev/r5VG/scoutapi-dev-root"   (n0,r12)
> /local/domain/0/backend/vbd/12/51713/domain = "scoutapi-dev"   (n0,r12)
> /local/domain/0/backend/vbd/12/51713/params = 
> "/dev/r5VG/scoutapi-dev-swap"   (n0,r12)
> /local/domain/0/backend/vif/12/0/domain = "scoutapi-dev"   (n0,r12)
> /local/domain/0/backend/console/12/0/domain = "scoutapi-dev"   (n0,r12)
> /local/domain/12/name = "scoutapi-dev"   (n0,r12)
>
>
> # DomU scoutapi-dev initially has assigned 256MB
> root@on05:~# xm list|grep scoutapi-dev
> scoutapi-dev                      12   256     1     -b----      8.8
>
> # ...and it can see that amount
> root@scoutapi-dev:~# free -m|grep -B 1 "Mem"
>        total       used       free     shared    buffers     cached
> Mem:     252         70        182          0          4         38
> root@scoutapi-dev:~# cat /proc/meminfo |grep MemTotal
> MemTotal:         258908 kB
> root@scoutapi-dev:~# cat 
> /sys/devices/system/xen_memory/xen_memory0/target_kb
> 262144
>
>
> # I increase scoutapi-dev's memory on Dom0
> root@on05:~# xm mem-set scoutapi-dev 512
> root@on05:~# xm list|grep scoutapi-dev
> scoutapi-dev                      12   512     1     -b----      9.0
>
> # DomU seems to be aware of the change (target_kb) but does not use it
> root@scoutapi-dev:~# free -m|grep -B 1 "Mem"
>          total       used       free     shared    buffers     cached
> Mem:       252         70        182          0          4         38
> root@scoutapi-dev:~# cat /proc/meminfo |grep MemTotal
> MemTotal:         258908 kB
> root@scoutapi-dev:~# cat 
> /sys/devices/system/xen_memory/xen_memory0/target_kb
> 262144
>
>
> # Now I reduce scoutapi-dev's memory
> root@on05:~# xm mem-set scoutapi-dev 128
> root@on05:~# xm list|grep scoutapi-dev
> scoutapi-dev                        12   128     1     -b----      9.1
>
> # DomU can see the change as expected
> root@scoutapi-dev:~# free -m|grep -B 1 "Mem"
>          total       used       free     shared    buffers     cached
> Mem:       128         70         58          0          4         38
> root@scoutapi-dev:~# cat /proc/meminfo |grep MemTotal
> MemTotal:         131676 kB
> root@scoutapi-dev:~# cat 
> /sys/devices/system/xen_memory/xen_memory0/target_kb
> 131072
>
> # Finally, I increase DomU memory to it's original size:
> root@on05:~# xm mem-set scoutapi-dev 256
> root@on05:~# xm list|grep scoutapi-dev
> scoutapi-dev                        12   256     1     -b----      9.2
>
> # DomU can see the increase fine, it seems to have problem
> # only if it the new size is bigger than the original.
> root@scoutapi-dev:~# free -m|grep -B 1 "Mem"
>          total       used       free     shared    buffers     cached
> Mem:       252         70        182          0          4         38
> root@scoutapi-dev:~# cat /proc/meminfo |grep MemTotal
> MemTotal:         258908 kB
> root@scoutapi-dev:~# cat 
> /sys/devices/system/xen_memory/xen_memory0/target_kb
> 262144
>
>
> # This is my config.
> # It has been created by xen-tools, but i use a custom
> # xen-tools.con and xm.tmpl
> root@on05:~# cat /etc/xen/scout-dev.cfg
> #
> # Configuration file for the Xen instance scout-dev, created
> # by xen-tools 4.2 on Tue Nov 13 19:02:28 2012.
>
> name        = 'scout-dev'
> memory      = '256'
> maxmem      = '8192'
> vcpus       = '1'
>
> kernel      = '/boot/vmlinuz-2.6.32-5-xen-amd64'
> ramdisk     = '/boot/initrd.img-2.6.32-5-xen-amd64'
>
> root        = '/dev/xvda2 ro'
> disk        = [
>                   'phy:/dev/r5VG/scout-dev-srv,xvda3,w',
>                   'phy:/dev/r5VG/scout-dev-root,xvda2,w',
>                   'phy:/dev/r5VG/scout-dev-swap,xvda1,w',
>               ]
> vif         = [
>                 'ip=11.22.33.44,mac=00:16:3E:72:7B:5A,bridge=xenbr55',
>               ]
> on_poweroff = 'destroy'
> on_reboot   = 'restart'
> on_crash    = 'restart'
>
> root@on05:~# dpkg -la|grep xen|awk '{print $1"\t "$2"\t"$3}'
> ii     libxenstore3.0    4.0.1-5.4
> ii     linux-image-2.6.32-5-xen-amd64    2.6.32-46
> ii     xen-hypervisor-4.0-amd64    4.0.1-5.4
> ii     xen-linux-system-2.6.32-5-xen-amd64    2.6.32-46
> ii     xen-qemu-dm-4.0    4.0.1-2+squeeze2
> ii     xen-tools    4.2-1
> ii     xen-utils-4.0    4.0.1-5.4
> ii     xen-utils-common    4.0.0-1
> ii     xenstore-utils    4.0.1-5.4
> ii     xenwatch    0.5.4-2
> root@on05:~# uname -a
> Linux on05 2.6.32-5-xen-amd64 #1 SMP Sun Sep 23 13:49:30 UTC 2012 
> x86_64 GNU/Linux
>
> If you can bring some light on it, that would be just wonderful.
>
> Greetings.
Hi Ian and Alexander,
it's good to hear I am not the onlyone experienced this issue.
The removal of tdb file solved the xenstore issue.
Now I am able to provide you the outputs you requested. They are very 
similar to those provided by Alexander.
server1:~# xenstore-ls -fp | grep ldap
/vm/2fad68ca-0fc8-b3ea-dac2-b54f713af36d/name = "ldap"   (n0)
/local/domain/0/backend/vbd/2/51713/domain = "ldap"   (n0,r2)
/local/domain/0/backend/vbd/2/51713/params = "system_vhosts/ldap-disk"   
(n0,r2)
/local/domain/0/backend/vbd/2/51714/domain = "ldap"   (n0,r2)
/local/domain/0/backend/vbd/2/51714/params = "system_vhosts/ldap-swap"   
(n0,r2)
/local/domain/0/backend/vbd/2/51715/domain = "ldap"   (n0,r2)
/local/domain/0/backend/vbd/2/51715/params = "system_vhosts/ldap-var"   
(n0,r2)
/local/domain/0/backend/vbd/2/51716/domain = "ldap"   (n0,r2)
/local/domain/0/backend/vbd/2/51716/params = 
"system_vhosts/ldap-varlog"   (n0,r2)
/local/domain/0/backend/vbd/2/51717/domain = "ldap"   (n0,r2)
/local/domain/0/backend/vbd/2/51717/params = "system_vhosts/ldap-tmp"   
(n0,r2)
/local/domain/0/backend/vbd/2/51718/domain = "ldap"   (n0,r2)
/local/domain/0/backend/vbd/2/51718/params = "system_vhosts/ldap-usr"   
(n0,r2)
/local/domain/0/backend/vif/2/0/domain = "ldap"   (n0,r2)
/local/domain/0/backend/vif/2/0/vifname = "ldap-pub"   (n0,r2)
/local/domain/0/backend/vif/2/1/domain = "ldap"   (n0,r2)
/local/domain/0/backend/vif/2/1/vifname = "ldap-pri"   (n0,r2)
/local/domain/0/backend/console/2/0/domain = "ldap"   (n0,r2)
/local/domain/2/name = "ldap"   (n0,r2)

I just increased the memory for ldap domU to 512MB:
ldap:~# grep MemTotal /proc/meminfo
MemTotal:         250320 kB
ldap:~# cat /sys/devices/system/xen_memory/xen_memory0/target_kb
262144
ldap:~# grep MemTotal /proc/meminfo
MemTotal:         250320 kB
ldap:~# cat /sys/devices/system/xen_memory/xen_memory0/target_kb
524288

but the real memory size didn't changed. Shrinking of the memory is 
working well - but I am not able to increase the size of the memory 
above the initial size.
Let me state once again, that this memory increase is working well with 
kernel 2.6.26-2-xen.
Hope we will be able to solve this issue.

Best regards,
--
Peter Viskup

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