Re: [Xen-devel] [PATCH] Prevent changing a memory size of Domain-0even if users make a careless mistake

[Masaki Kanno <kanno.masaki@xxxxxxxxxxxxxx>]

Mon, 7 Apr 2008 01:56:02 +0100, Mark Williamson wrote:

>> Is it?  As far as I know, the current meaning of dom0-min-mem set to 0
>> is "No ballooning".  There are the following comments about dom0-min-mem
>> in xend-config.sxp.
>>
>> # Dom0 will balloon out when needed to free memory for domU.
>> # dom0-min-mem is the lowest memory level (in MB) dom0 will get down to.
>> # If dom0-min-mem=0, dom0 will never balloon out.
>
>Sorry, think I hadn't had enough coffee!  You're right of course.  Plus, 
>your 
>suggested behaviour is more consistent.
>
>On the face of it, disabling ballooning like this seems inconvenient.  
>However, I'd think that if disabling auto-ballooning, the administrator has 
>probably set their dom0 footprint manually on the Xen command line, so they 
>won't want to mem-set it anyhow.
>
>Admins who want to be able to mess about arbitrarily with memory can still 
>put 
>dom0-min-mem=1.  I think dom0-min-mem should really /mean/ dom0-min-mem as 
>far as the control tools are concerned.  If we want to disable 
>autoballooning 
>independently of mem-set, we could add a simple boolean option.

Hi Mark,

Thanks for your suggestion.  It is good suggestion.
I will write a patch according to your suggestion.

Best regards,
 Kan

>
>Cheers,
>Mark
>
>> Best regards,
>>  Kan
>>
>> >Cheers,
>> >Mark
>> >
>> >+                    raise XendError("memory_dynamic_max cannot be changed
>> >for
>> >safety reasons")
>> >+
>> >         self._safe_set_memory('memory_dynamic_min', target * MiB)
>> >         self._safe_set_memory('memory_dynamic_max', target * MiB)
>> >
>> >>  -- Keir
>> >>
>> >> On 4/4/08 11:06, "Masaki Kanno" <kanno.masaki@xxxxxxxxxxxxxx> wrote:
>> >> > Hi,
>> >> >
>> >> > If users accidentally change a memory size of Domain-0 to very small
>> >> > memory size by xm mem-set command, users will be not able to operate
>> >> > Domain-0.  I think that Domain-0 is important for Xen, so I'd like to
>> >> > prevent the accident by xm mem-set command.
>> >> >
>> >> > This patch prevents changing the memory size of Domain-0 by xm mem-set
>> >> > command if specified memory size is smaller than dom0-min-mem in
>> >> > xend-config.sxp.
>> >> >
>> >> >  # cat /etc/xen/xend-config.sxp | grep "(dom0-min-mem"
>> >> >  (dom0-min-mem 384)
>> >> >  # xm list Domain-0
>> >> >  Name                                        ID   Mem VCPUs      State
>> >> > Time(s)
>> >> >  Domain-0                                     0   941     2     r-----
>> >> > 62.6
>> >> >  # xm mem-set Domain-0 1
>> >> >  Error: memory_dynamic_max cannot be changed for safety reasons
>> >> >  Usage: xm mem-set <Domain> <Mem>
>> >> >
>> >> >  Set the current memory usage for a domain.
>> >> >  # xm list Domain-0
>> >> >  Name                                        ID   Mem VCPUs      State
>> >> > Time(s)
>> >> >  Domain-0                                     0   941     2     r-----
>> >> > 63.6
>> >> >
>> >> >
>> >> > Signed-off-by: Masaki Kanno <kanno.masaki@xxxxxxxxxxxxxx>
>> >> >
>> >> > Best regards,
>> >> >  Kan
>> >> >
>> >> > _______________________________________________
>> >> > Xen-devel mailing list
>> >> > Xen-devel@xxxxxxxxxxxxxxxxxxx
>> >> > http://lists.xensource.com/xen-devel
>> >>
>> >> _______________________________________________
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>> >
>> >--
>> >Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/
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>> >
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>
>
>
>-- 
>Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/
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