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Re: [Xen-users] dom0 memory limitation not working in Debian sid install of XCP

Yep, I got that problem just yesterday.

1st: you put dom0_mem option in wrong place. This is not a linux option, but hypervisor one.

Correct grub config looks like this:

submenu "Xen 4.1-amd64" {
menuentry 'Debian GNU/Linux, with Xen 4.1-amd64 and Linux 3.1.0-1-amd64' --class debian --class gnu-linux --class gnu --class os --class xen {
ÂÂÂÂÂÂÂ insmod part_msdos
ÂÂÂÂÂÂÂ insmod ext2
ÂÂÂÂÂÂÂ set root='(hd0,msdos1)'
ÂÂÂÂÂÂÂ search --no-floppy --fs-uuid --set=root b26ab79c-352a-4305-b779-ae3b92591f62
ÂÂÂÂÂÂÂ echoÂÂÂ 'Loading Xen 4.1-amd64 ...'
 multiboot /boot/xen-4.1-amd64.gz placeholder dom0_mem=2048M
ÂÂÂÂÂÂÂ echoÂÂÂ 'Loading Linux 3.1.0-1-amd64 ...'
 module /boot/vmlinuz-3.1.0-1-amd64 placeholder root=UUID=b26ab79c-352a-4305-b779-ae3b92591f62 ro quiet dom0_mem=1024M
ÂÂÂÂÂÂÂ echoÂÂÂ 'Loading initial ramdisk ...'
 module /boot/initrd.img-3.1.0-1-amd64

2nd: pv_ops kernels use different ballooning policy, so you need to raise amount, alllocated to VM to get same dom0 TotalMem as with -xen kernels (like in ISO-based xcp). So, use at least 1Gb for dom0_mem.

P.S. Does anyone know what is that 'placeholder' stuff for?

On 08.01.2012 00:54, JoÃo LuÃs Pinto wrote:

I have installed XCP in Debian following the steps depicted in

Out of the box, dom0 takes hold of all the available memory, so I
cannot start any domU (I'm using XenCenter). If I try to limit the
dom0 memory using kernel parameter dom0_mem, it is apparently ignored.


# cat /proc/cmdline

placeholder root=/dev/mapper/god-root ro dom0_mem=1024M dom0_max_vcpus=2 quiet

# uname -r


# xm list

Name                                        ID   Mem VCPUs      State   Time(s)
Domain-0                                     0 15780     8     r-----     24.6

# xm info

host                   : god
release                : 3.1.0-1-amd64
version                : #1 SMP Fri Dec 23 16:37:11 UTC 2011
machine                : x86_64
nr_cpus                : 8
nr_nodes               : 1
cores_per_socket       : 4
threads_per_core       : 2
cpu_mhz                : 3192
hw_caps                :
virt_caps              : hvm hvm_directio
total_memory           : 16374
free_memory            : 623
free_cpus              : 0
xen_major              : 4
xen_minor              : 1
xen_extra              : .2
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : unavailable
xen_commandline        : placeholder
cc_compiler            : gcc version 4.6.2 (Debian 4.6.2-7)
cc_compile_by          : jon
cc_compile_domain      : frankenelmo.uk.xensource.com
cc_compile_date        : Mon Dec 12 12:33:32 UTC 2011
xend_config_format     : 4

# xe vm-list params

uuid ( RO)                          : 1edcd68f-5fc7-d16e-922a-23c503e02adf
                    name-label ( RW): Control domain on host: god
              name-description ( RW): The domain which manages
physical devices and manages other domains
                  user-version ( RW): 1
                 is-a-template ( RW): false
                 is-a-snapshot ( RO): false
                   snapshot-of ( RO): <not in database>
                     snapshots ( RO):
                 snapshot-time ( RO): 19700101T00:00:00Z
                 snapshot-info ( RO):
                        parent ( RO): <not in database>
                      children ( RO):
             is-control-domain ( RO): true
                   power-state ( RO): running
                 memory-actual ( RO): 16287358976
                 memory-target ( RO): <expensive field>
               memory-overhead ( RO): 149946368
             memory-static-max ( RW): 17976631296
            memory-dynamic-max ( RW): 1399848960
            memory-dynamic-min ( RW): 1399848960
             memory-static-min ( RW): 1399848960
              suspend-VDI-uuid ( RW): <not in database>
               suspend-SR-uuid ( RW): <not in database>
                  VCPUs-params (MRW):
                     VCPUs-max ( RW): 8
              VCPUs-at-startup ( RW): 8
        actions-after-shutdown ( RW): Destroy
          actions-after-reboot ( RW): Destroy
           actions-after-crash ( RW): Destroy
                 console-uuids (SRO): f6dee123-0274-b4e1-e04f-7cbd1e124139
                      platform (MRW):
            allowed-operations (SRO): changing_dynamic_range
            current-operations (SRO):
            blocked-operations (MRW):
           allowed-VBD-devices (SRO): <expensive field>
           allowed-VIF-devices (SRO): <expensive field>
                possible-hosts ( RO): <expensive field>
               HVM-boot-policy ( RW):
               HVM-boot-params (MRW):
         HVM-shadow-multiplier ( RW): 1.000
                     PV-kernel ( RW):
                    PV-ramdisk ( RW):
                       PV-args ( RW):
                PV-legacy-args ( RW):
                 PV-bootloader ( RW):
            PV-bootloader-args ( RW):
           last-boot-CPU-flags ( RO):
              last-boot-record ( RO): <expensive field>
                   resident-on ( RO): 62a2054f-8340-850a-9e02-901e853f6d0d
                      affinity ( RW): 62a2054f-8340-850a-9e02-901e853f6d0d
                  other-config (MRW): storage_driver_domain:
OpaqueRef:c165ca60-9c6a-9161-0006-99aedec5ef9c; is_system_domain: true
                        dom-id ( RO): 0
               recommendations ( RO):
                 xenstore-data (MRW):
    ha-always-run ( RW) [DEPRECATED]: false
           ha-restart-priority ( RW):
                         blobs ( RO):
                    start-time ( RO): 19700101T00:00:00Z
                  install-time ( RO): 19700101T00:00:00Z
                  VCPUs-number ( RO): 8
             VCPUs-utilisation (MRO): <expensive field>
                    os-version (MRO): <not in database>
            PV-drivers-version (MRO): <not in database>
         PV-drivers-up-to-date ( RO): <not in database>
                        memory (MRO): <not in database>
                         disks (MRO): <not in database>
                      networks (MRO): <not in database>
                         other (MRO): <not in database>
                          live ( RO): <not in database>
    guest-metrics-last-updated ( RO): <not in database>
                   cooperative ( RO): <expensive field>
             protection-policy ( RW): <not in database>
         is-snapshot-from-vmpp ( RO): false
                          tags (SRW):
                     appliance ( RW): <not in database>
                   start-delay ( RW): 0
                shutdown-delay ( RW): 0
                         order ( RW): 0
                       version ( RO): 0

dmesg is attached.

Thank you for any help. I will gladly provide any additionally
required information.

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