xen discuss - Aug 2007 - Info request - allocation the dom0_mem for a 1GB RAM laptop

Hello all:

I''ve managed to install b66-xen on my Dell Latitude D620 (T7200 - 64
bit - 1GB RAM).

On other Dell boxes that have 4 GB of RAM, I didn''t have to change
anything apart from starting the four services as mentioned here :
http://blogs.sun.com/cwb/entry/starting_out_with_solaris_on

I was able to succesfully run two XP instances on a core each, and a
native XP instance on another core on a quad core box.

On my laptop, however, I have just 1 GB of RAM.

I have enabled VT in the BIOS. When I attemp to create a domain, xen
complains something along the lines of "I need 1058698 KiB, but
dom0_min_mem is 262144 and shrinking to 262144 KiB would leave only
235124 KiB free"

I tried setting dom0_mem in the grub entry to various numbers.
However, xm either complains about insufficient memory as above, or
Solaris freezes, or the laptop just doesn''t boot up.

What should I be reading so that I make better educated configuration
changes instead of setting values at random ?

-- Sriram

Sriram Narayanan wrote:
> Hello all:
> 
> I''ve managed to install b66-xen on my Dell Latitude D620 (T7200 -
64
> bit - 1GB RAM).
> 
> On other Dell boxes that have 4 GB of RAM, I didn''t have to change
> anything apart from starting the four services as mentioned here :
> http://blogs.sun.com/cwb/entry/starting_out_with_solaris_on
> 
> I was able to succesfully run two XP instances on a core each, and a
> native XP instance on another core on a quad core box.
> 
> On my laptop, however, I have just 1 GB of RAM.
> 
> I have enabled VT in the BIOS. When I attemp to create a domain, xen
> complains something along the lines of "I need 1058698 KiB, but
> dom0_min_mem is 262144 and shrinking to 262144 KiB would leave only
> 235124 KiB free"
What is the "memory" line in your .py file?  1058698 KiB is over 1 GB.

You probably want to tune that down to 512 MB, and let dom0 auto-balloon 
down (or set dom0_mem to 512 MB).
> 
> I tried setting dom0_mem in the grub entry to various numbers.
> However, xm either complains about insufficient memory as above, or
> Solaris freezes, or the laptop just doesn''t boot up.
> 
> What should I be reading so that I make better educated configuration
> changes instead of setting values at random ?
Figuring out the memory configuration is not easy.  It depends on what you 
want to run in each domain, and how many virtual domains you want to run on 
a machine.  It''s something we''re still trying to figure out,
so we have not
written much documentation on it yet.

-Ryan
> 
> -- Sriram
> _______________________________________________
> xen-discuss mailing list
> xen-discuss@opensolaris.org

On 8/21/07, Ryan Scott <Ryan.Scott@sun.com> wrote:
> Sriram Narayanan wrote:
> > Hello all:
> >
> > I''ve managed to install b66-xen on my Dell Latitude D620
(T7200 - 64
> > bit - 1GB RAM).
> >
> > On other Dell boxes that have 4 GB of RAM, I didn''t have to
change
> > anything apart from starting the four services as mentioned here :
> > http://blogs.sun.com/cwb/entry/starting_out_with_solaris_on
> >
> > I was able to succesfully run two XP instances on a core each, and a
> > native XP instance on another core on a quad core box.
> >
> > On my laptop, however, I have just 1 GB of RAM.
> >
> > I have enabled VT in the BIOS. When I attemp to create a domain, xen
> > complains something along the lines of "I need 1058698 KiB, but
> > dom0_min_mem is 262144 and shrinking to 262144 KiB would leave only
> > 235124 KiB free"
>
> What is the "memory" line in your .py file?  1058698 KiB is over
1 GB.
>
I have changed it to 256 and continued then SXCE just hung. I had to
power off and reboot, and now the xend is marked "maintenance", while
console and domains are marked "offline".

I tried to enable these three, but with no success.
> You probably want to tune that down to 512 MB, and let dom0 auto-balloon
> down (or set dom0_mem to 512 MB).
>
What''d be the correct syntax for setting dom0_mem ? I''ve tried
both of
"dom0_mem=512MB" as well as "dom0_mem=524288"
> >
> > I tried setting dom0_mem in the grub entry to various numbers.
> > However, xm either complains about insufficient memory as above, or
> > Solaris freezes, or the laptop just doesn''t boot up.
> >
> > What should I be reading so that I make better educated configuration
> > changes instead of setting values at random ?
>
> Figuring out the memory configuration is not easy.  It depends on what you
> want to run in each domain, and how many virtual domains you want to run on
> a machine.  It''s something we''re still trying to figure
out, so we have not
> written much documentation on it yet.
>
For now, this is a single Windows XP instance based on the native
install. This works just fine on my desktop that has 4GB RAM
> -Ryan
>
> >
> > -- Sriram
> > _______________________________________________
> > xen-discuss mailing list
> > xen-discuss@opensolaris.org
>
>

Sriram Narayanan wrote:
> On 8/21/07, Ryan Scott <Ryan.Scott@sun.com> wrote:
>> Sriram Narayanan wrote:
>>> Hello all:
>>>
>>> I''ve managed to install b66-xen on my Dell Latitude D620
(T7200 - 64
>>> bit - 1GB RAM).
>>>
>>> On other Dell boxes that have 4 GB of RAM, I didn''t have
to change
>>> anything apart from starting the four services as mentioned here :
>>> http://blogs.sun.com/cwb/entry/starting_out_with_solaris_on
>>>
>>> I was able to succesfully run two XP instances on a core each, and
a
>>> native XP instance on another core on a quad core box.
>>>
>>> On my laptop, however, I have just 1 GB of RAM.
>>>
>>> I have enabled VT in the BIOS. When I attemp to create a domain,
xen
>>> complains something along the lines of "I need 1058698 KiB,
but
>>> dom0_min_mem is 262144 and shrinking to 262144 KiB would leave only
>>> 235124 KiB free"
>> What is the "memory" line in your .py file?  1058698 KiB is
over 1 GB.
>>
> 
> I have changed it to 256 and continued then SXCE just hung. I had to
> power off and reboot, and now the xend is marked "maintenance",
while
> console and domains are marked "offline".
''svcs -l xctl/xend'' will give you a logfile line, which I
think should be
/var/svc/log/system-xctl-xend:default.log

Is there anything in that file that explains why it is not starting?
> 
> I tried to enable these three, but with no success.
> 
>> You probably want to tune that down to 512 MB, and let dom0
auto-balloon
>> down (or set dom0_mem to 512 MB).
>>
> 
> What''d be the correct syntax for setting dom0_mem ? I''ve
tried both of
> "dom0_mem=512MB" as well as "dom0_mem=524288"
If no units are provided, the number is assumed to be kB.  So 
"dom0_mem=524288" would set it at 512 MB.  Note that this must go on
the
"kernel$" line in the menu.lst entry, not one of the
"module$" lines.

-Ryan
> 
>>> I tried setting dom0_mem in the grub entry to various numbers.
>>> However, xm either complains about insufficient memory as above, or
>>> Solaris freezes, or the laptop just doesn''t boot up.
>>>
>>> What should I be reading so that I make better educated
configuration
>>> changes instead of setting values at random ?
>> Figuring out the memory configuration is not easy.  It depends on what
you
>> want to run in each domain, and how many virtual domains you want to
run on
>> a machine.  It''s something we''re still trying to
figure out, so we have not
>> written much documentation on it yet.
>>
> 
> For now, this is a single Windows XP instance based on the native
> install. This works just fine on my desktop that has 4GB RAM
> 
>> -Ryan
>>
>>> -- Sriram
>>> _______________________________________________
>>> xen-discuss mailing list
>>> xen-discuss@opensolaris.org
>>
> _______________________________________________
> xen-discuss mailing list
> xen-discuss@opensolaris.org

On 8/21/07, Sriram Narayanan <sriramnrn@gmail.com> wrote:
>
> I have enabled VT in the BIOS. When I attemp to create a domain, xen
> complains something along the lines of "I need 1058698 KiB, but
> dom0_min_mem is 262144 and shrinking to 262144 KiB would leave only
> 235124 KiB free"
>
> I tried setting dom0_mem in the grub entry to various numbers.
> However, xm either complains about insufficient memory as above, or
> Solaris freezes, or the laptop just doesn''t boot up.
>
I faced this problem on a Fedora 7 install. I altered
/etc/xen/xend-config.sxp such that it now contained (dom0-min-mem 192)

On my Solaris instance, I managed to get Solaris to hang, and then had
to switch the laptop off. Upon reboot, I saw that some database got
corrupted. I intend to find out just which database that is, and to
try and resolve that issue.

-- Sriram

Sriram Narayanan wrote:
> On 8/21/07, Ryan Scott wrote:
> > What is the "memory" line in your .py file? 1058698 KiB is
over 1 GB.
> >
> I have changed it to 256 and continued then SXCE just hung. I had to
> power off and reboot, ...
I''ve also observed Solaris Dom0 hangs, on a 768MB system, when trying
to create a 192MB DomU.

In my case, the root cause appears to be an endless loop in the dom0
balloon code. The balloon_worker_thread never releases the cpu when
"availrmem" gets low while reducing a domain''s memory
reservation.

Possible workaround:  Change the kernel tunable "bln_wait_sec" from 0
to 1, before starting the first domU.  E.g.

    echo ''bln_wait_sec/W 1'' | mdb -wk

    xm create -c ....
 
 
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