Dear Guys,
First of all thanks for all your wise replies.. a little late since was tied with some other stuff and wanted to test the change I made on my xen server
actually as dennis says ... and hes perfectly right
actually what I did was restrict my DOM0 mem size to 1 gb with dom0_mem=1024M in grub.conf and now top and free was showing 1 gb as my memory. also i have disabled balloning in the xend-config file as recommended
and xm top and xm info were showing me 64 gb as total memory and the free memory and the memory used by my V.Ms was equall to 64 gb which is perfect
So I am now clear that free and top actually shows the memory assigned to DOM 0 and not the totalsystem memory under xen
Once again thaks and apprecite your responses guys..
regards
sylvan
On Sat, Aug 27, 2011 at 3:44 PM, Dennis Jacobfeuerborn <dennisml@xxxxxxxxxxxx> wrote:
Benedict is right. Remember that under Xen Dom0 is really just another VMOn 08/27/2011 02:35 PM, Simon Matter wrote:
>> Thanks Guys
>>
>> really apprecite your quick responses.
>> ( Dennis was right in tellin me about PAE since my system is 64 bit and if
>> I
>> do run yum install kernel-PAE there is nothing found.)
>>
>> actually i found something more as i was figuring my issue out.
>>
>> when I do a top i see the following
>> ---------------
>>
>> Tasks: 285 total, 1 running, 284 sleeping, 0 stopped, 0 zombie
>> Cpu(s): 0.0%us, 0.0%sy, 0.0%ni, 99.8%id, 0.2%wa, 0.0%hi, 0.0%si,
>> 0.0%st
>> Mem: 33554432k total, 15430836k used, 18123596k free, 323176k buffers
>> Swap: 2819396k total, 0k used, 2819396k free, 13860960k cached
>> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
>> ---------------
>>
>> when I run cat /proc/meminfo i see
>>
>> ----MemTotal: 33554432 kB
>> MemFree: 18123588 kB
>> Buffers: 323192 kB
>> Cached: 13860992 kB
>> SwapCached: 0 kB
>> Active: 9601264 kB
>> Inactive: 4643904 kB
>> HighTotal: 0 kB
>> HighFree: 0 kB
>> LowTotal: 33554432 kB
>> LowFree: 18123588 kB
>> SwapTotal: 2819396 kB
>> SwapFree: 2819396 kB
>> Dirty: 8 kB
>> Writeback: 0 kB
>> AnonPages: 60972 kB
>> Mapped: 12528 kB
>> Slab: 360860 kB
>> PageTables: 18444 kB
>> NFS_Unstable: 0 kB
>> Bounce: 0 kB
>> CommitLimit: 19596612 kB
>> Committed_AS: 394740 kB
>> VmallocTotal: 34359738367 kB
>> VmallocUsed: 3304 kB
>> VmallocChunk: 34359733919 kB
>> ------------
>>
>> actually I had run the above 2 command and found the memory was 32gb
>> but as dennis said when I run the command
>> xm info
>> ----------------------
>> [root@hypervisor2 ~]# xm info
>> host : hypervisor2
>> release : 2.6.18-194.32.1.el5xen
>> version : #1 SMP Wed Jan 5 18:44:24 EST 2011
>> machine : x86_64
>> nr_cpus : 16
>> nr_nodes : 1
>> sockets_per_node : 2
>> cores_per_socket : 4
>> threads_per_core : 2
>> cpu_mhz : 2527
>> hw_caps :
>> bfebfbff:28100800:00000000:00000140:009ce3bd:00000000:00000001
>> total_memory : 65527
>> free_memory : 22989
>> node_to_cpu : node0:0-15
>> xen_major : 3
>> xen_minor : 1
>> xen_extra : .2-194.32.1.el5
>> 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_pagesize : 4096
>> platform_params : virt_start=0xffff800000000000
>> xen_changeset : unavailable
>> cc_compiler : gcc version 4.1.2 20080704 (Red Hat 4.1.2-48)
>> cc_compile_by : mockbuild
>> cc_compile_domain : centos.org
>> cc_compile_date : Wed Jan 5 17:43:03 EST 2011
>> xend_config_format : 2
>> --------------------
>> and then I ran xm top i see
>>
>> -------------
>>
>> 5 domains: 1 running, 4 blocked, 0 paused, 0 crashed, 0 dying, 0 shutdown
>> Mem: 67099744k total, 43558844k used, 23540900k free CPUs: 16 @ 2527MHz
>> NAME STATE CPU(sec) CPU(%) MEM(k) MEM(%) MAXMEM(k) MAXMEM(%)
>> VCPUS NETS NETTX(k) NETRX(k) VBDS VBD_OO VBD_RD VBD
>> _WR SSID
>> Domain-0 -----r 8401 2.4 33554688 50.0 no limit
>> n/a 16 4 1892 16848120 0 0 0
>> 0 0
>> sepmback --b--- 9758 2.6 2105220 3.1 4210688
>> 6.3 4 1 0 0 1 0 0
>> 0 0
>> winserver2 --b--- 5758 0.9 1056644 1.6 4210688
>> 6.3 1 1 0 0 1 0 0
>> 0 0
>> wsusserver --b--- 25812 11.4 3256196 4.9 8404992
>> 12.5 4 1 0 0 1 0 0
>> 0 0
>> zimbra --b--- 26183 7.8 2105220 3.1 4210688
>> 6.3 4 1 0 16 1 0 0
>> 0 0
>> ----------------------
>>
>> so the above 2 command show me 64gb
>>
>> Now I m confused ..
>>
>> Is my Centos XEN server actually using the 64 bit ...
>> and which command actually show me the right memory status
>
> I'm not sure but I think everything is okay with your box. "xm top" shows
> that your box run with 64Gb memory, and what "top" shows is that your Dom0
> OS runs with 32Gb memory, which means your DomU's take the other 32Gb. Did
> you up the memory settings in your virtual hosts configuration? After
> doing so you should see the Dom0 memory to go down when looking at it with
> "top".
with special privileges. In fact on all my host systems I restrict Dom0 to
1G of ram by adding a "dom0_mem=1024M" argument to the grub configuration.
In practice Xen should reduce the amount of ram used by Dom0 dynamically as
needed for VMs i.e. if your virtual machines use 48G of ram then dom0
should only show 16G left. A while ago this mechanism lead to instability
though so a general recommendation was to set dom0 memory to a fixed 1G or
512M to not rely on this dynamic memory handling.
Check this out for example:
http://lists.xensource.com/archives/html/xen-users/2008-06/msg00729.html
Regards,
Dennis
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