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Dom0 Memory?

 

 

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cobrahost at hotmail

May 9, 2012, 1:43 AM

Post #1 of 37 (3404 views)
Permalink
Dom0 Memory?

Hello,

System has the following Config.

2x E5620
98GB Memory

What would you suggest the best value for dom0_mem= would be for this type of system?
Set it to 4GB of memory now on each one.

Just before the server would freeze and the IPMI returned a back screen, so not completely sure.


fbcyborg at gmail

May 9, 2012, 1:53 AM

Post #2 of 37 (3353 views)
Permalink
Re: Dom0 Memory? [In reply to]

On 9 May 2012 10:43, CobraHost <cobrahost [at] hotmail> wrote:
> Hello,
>
> System has the following Config.
>
> 2x E5620
> 98GB Memory
>
> What would you suggest the best value for dom0_mem= would be for this type
> of system?
> Set it to 4GB of memory now on each one.
Hi!
I think it should be a good value, considering you have 98GB of RAM, but let me
make you a question please: once you've booted the system, do you see all the
98GB available if you do 'cat /proc/meminfo' or 'free'?

Regards,
--
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fbcyborg at gmail

May 9, 2012, 1:57 AM

Post #3 of 37 (3348 views)
Permalink
Re: Dom0 Memory? [In reply to]

On 9 May 2012 10:54, CobraHost <cobrahost [at] hotmail> wrote:
> cat /proc/meminfo
> MemTotal:      4194304 kB
This doesn't seem to be the total amount of RAM you have on
your system, which is actually 98GB.

Please remember to Cc the list.
--
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fbcyborg at gmail

May 9, 2012, 2:02 AM

Post #4 of 37 (3366 views)
Permalink
Re: Dom0 Memory? [In reply to]

On 9 May 2012 10:58, CobraHost <cobrahost [at] hotmail> wrote:
> Hello,
>
> Appended the grub line with domo_mem=4096m
Yes, I did understand.
I was talking about this issue:
http://lists.xen.org/archives/html/xen-users/2011-12/msg00069.html

--
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fbcyborg at gmail

May 9, 2012, 2:43 AM

Post #5 of 37 (3351 views)
Permalink
Re: Dom0 Memory? [In reply to]

On 9 May 2012 11:08, CobraHost <cobrahost [at] hotmail> wrote:
> Hello,
Could you Cc the list please?

>
> when you modify the grub.conf with dom0_mem=4096m it won't show the total
> memory amount.
Yes, I know but if I put dom0_mem=1024M, I see the dom0 has 1GB of RAM, and
free (or cat /proc/meminfo) gives me only 300MB of free RAM and it
should give me
3GB of free RAM since I have a total amount of 4GB on my system.

For this reason I was asking this.
--
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fbcyborg at gmail

May 9, 2012, 2:51 AM

Post #6 of 37 (3355 views)
Permalink
Re: Dom0 Memory? [In reply to]

On 9 May 2012 11:47, CobraHost <cobrahost [at] hotmail> wrote:
> Hello,
>
> I'm guessing this has something to do with the kernel we are using since it
> is majorly outdated. and we are running RHEL 5.8
Yes, and as far as I know this problem is still not fixed.
No more news from the dev team.

PS: I don't know if you reply to the list including the list address in the
Bcc field, but I would ask you to always include the list address in the
Cc field, because I see every reply from you only directed to me.
Thank you.

--
Flavio

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Matthew.Wild at stfc

May 9, 2012, 4:32 AM

Post #7 of 37 (3328 views)
Permalink
Re: Dom0 Memory? [In reply to]

On 09/05/12 10:43, Flavio wrote:
> On 9 May 2012 11:08, CobraHost<cobrahost [at] hotmail> wrote:
>> Hello,
> Could you Cc the list please?
>
>>
>> when you modify the grub.conf with dom0_mem=4096m it won't show the total
>> memory amount.
> Yes, I know but if I put dom0_mem=1024M, I see the dom0 has 1GB of RAM, and
> free (or cat /proc/meminfo) gives me only 300MB of free RAM and it
> should give me
> 3GB of free RAM since I have a total amount of 4GB on my system.
>
Surely, since you've given dom0 only 1024M, it's correct for
/proc/meminfo to return 1GB.

What does 'xm info' say?

That should tell you how much memory Xen thinks it has to work with.

Matthew

--
Scanned by iCritical.
Attachments: Matthew_Wild.vcf (0.35 KB)


fbcyborg at gmail

May 9, 2012, 4:38 AM

Post #8 of 37 (3338 views)
Permalink
Re: Dom0 Memory? [In reply to]

On 9 May 2012 13:32, Matthew Wild <Matthew.Wild [at] stfc> wrote:
> Surely, since you've given dom0 only 1024M, it's correct for /proc/meminfo
> to return 1GB.
No, it doesn't return 1GB. It returns about 300MegaBytes and such value
may vary.

--
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Matthew.Wild at stfc

May 9, 2012, 4:49 AM

Post #9 of 37 (3346 views)
Permalink
Re: Dom0 Memory? [In reply to]

On 09/05/12 12:38, Flavio wrote:
> On 9 May 2012 13:32, Matthew Wild<Matthew.Wild [at] stfc> wrote:
>> Surely, since you've given dom0 only 1024M, it's correct for /proc/meminfo
>> to return 1GB.
> No, it doesn't return 1GB. It returns about 300MegaBytes and such value
> may vary.
>
MemTotal: or MemFree:?

What does 'xm info' say?

Matthew

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Attachments: Matthew_Wild.vcf (0.35 KB)


fbcyborg at gmail

May 9, 2012, 8:52 AM

Post #10 of 37 (3325 views)
Permalink
Re: Dom0 Memory? [In reply to]

On 9 May 2012 13:49, Matthew Wild <Matthew.Wild [at] stfc> wrote:
> MemTotal: or MemFree:?
I've set dom0_mem=1024M
If I try to start XEN on my laptop, which has 8GB of RAM, I get:
MemTotal: 819316 kB <---- which is approximately 0.78GByte !!!
MemFree: 662416 kB <------ o.0 ???

===================================
same as above

# free
total used free
Mem: 819316 157260 662056

===================================

And this is OK:
# xl list
Name ID Mem
Domain-0 0 1023

===================================

>
>
> What does 'xm info' say?
# xl info
total_memory : 8107
free_memory : 6968


As you can see, my 8GB of RAM have disappeared.
What can you say about that?
--
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raistlin at linux

May 10, 2012, 3:38 AM

Post #11 of 37 (3330 views)
Permalink
Re: Dom0 Memory? [In reply to]

On Wed, 2012-05-09 at 17:52 +0200, Flavio wrote:
> > What does 'xm info' say?
> # xl info
> total_memory : 8107
> free_memory : 6968
>
So, 8GB of RAM is what Xen knows, ~7 of them being free... What's the
problem?

> As you can see, my 8GB of RAM have disappeared.
> What can you say about that?
>
Uh? :-O

Ok, this might be a bit too technical, but perhaps still of help:
http://blog.xen.org/index.php/2012/04/30/do%EF%BB%BFm0-memory-where-it-has-not-gone/

I'm also sure this has been mentioned in this or another thread related
to this "issue":
http://wiki.xen.org/wiki/Xen_Best_Practices
http://wiki.xen.org/wiki/Xen_Best_Practices#Why_should_I_dedicate_fixed_amount_of_memory_for_Xen_dom0.3F

Also trying to quickly summarize what's happening, no, your memory
_has_not_ disappeared. Actually, it is right there for your VMs to use
it (and xl invocation above shows right that).

With dom0_mem=1G you told Xen that one of your VM (the one that it will
automatically call 'Domain0' and that it will automatically create on
boot) will use 1G of your 8G of RAM. If you now try to create another VM
(say 'VM_1') with 2G of RAM, it will just do that, and you'll have 1G
+2G=3G out of 8G of your RAM dedicated to these two VMs, while the other
5G are still free.

Have you tried that? If you do, try running `xl info' on Dom0 again
after that. Try also SSH-ing in 'VM_1' and asking (e.g., via `free -m')
how many total and free memory it has. As one should expect, it will say
it has 2GB of RAM in total... Does this make sense?

So, again, the reason why you're not seeing 7GB of RAM in Dom0 is
because they're not there! Dom0 is a virtual machine to which you've
given 1GB of RAM via the cmdline... Having only 1GB of RAM is just doing
right what you asked for!

I can understand that it might look a bit tricky, but what you seem to
be missing here is you should consider Dom0 pretty much like any other
VM that Xen is managing as the hypervisor.

Hope of being of some help.

Regards,
Dario
--
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://retis.sssup.it/people/faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)
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fbcyborg at gmail

May 10, 2012, 5:20 AM

Post #12 of 37 (3390 views)
Permalink
Re: Dom0 Memory? [In reply to]

On 10 May 2012 12:38, Dario Faggioli <raistlin [at] linux> wrote:
> On Wed, 2012-05-09 at 17:52 +0200, Flavio wrote:
>> > What does 'xm info' say?
>> # xl info
>> total_memory           : 8107
>> free_memory            : 6968
>>
> So, 8GB of RAM is what Xen knows, ~7 of them being free... What's the
> problem?
Yes, but as far as I can see, even if xl info gives me such values,
the real amount
of free RAM is very less than it declares. I've reported also the free and the
cat /proc/meminfo output on the purpose and what I can see, practically, is that
I cannot run Chromium, or other "big" applications because of this lack of free
RAM. This is an issue that has been confirmed many months ago.

>
>> As you can see, my 8GB of RAM have disappeared.
>> What can you say about that?
>>
> Uh? :-O
If you look at xl info, you are right when you do this face, but
the practical issues that I am facing with, confirm that there is
something not working properly, when the hypervisor is running.

>
> Ok, this might be a bit too technical, but perhaps still of help:
> http://blog.xen.org/index.php/2012/04/30/do%EF%BB%BFm0-memory-where-it-has-not-gone/
Thanks, but this didn't help me to fix the problem.

>
> I'm also sure this has been mentioned in this or another thread related
> to this "issue":
> http://wiki.xen.org/wiki/Xen_Best_Practices
> http://wiki.xen.org/wiki/Xen_Best_Practices#Why_should_I_dedicate_fixed_amount_of_memory_for_Xen_dom0.3F
Already seen that a lot of times.

>
> Also trying to quickly summarize what's happening, no, your memory
> _has_not_ disappeared. Actually, it is right there for your VMs to use
> it (and xl invocation above shows right that).
OK, I was just only wandering why I was experiencing system slow downs, as
reported above. I don't know what would happen if several VMs would be running
at the same time.

>
> With dom0_mem=1G you told Xen that one of your VM (the one that it will
> automatically call 'Domain0' and that it will automatically create on
> boot) will use 1G of your 8G of RAM. If you now try to create another VM
> (say 'VM_1') with 2G of RAM, it will just do that, and you'll have 1G
> +2G=3G out of 8G of your RAM dedicated to these two VMs, while the other
> 5G are still free.
Great. This is perfectly clear now. But you would certainly understand my
perplexity when I see only 662416 kB of free memory in cat /proc/meminfo.
That is smaller than 5GB you mentioned above.

>
> Have you tried that? If you do, try running `xl info' on Dom0 again
> after that. Try also SSH-ing in 'VM_1' and asking (e.g., via `free -m')
> how many total and free memory it has. As one should expect, it will say
> it has 2GB of RAM in total... Does this make sense?
Sure it has. I don't have anything to say about that actually. If my domUs
have the right amount of RAM I decided to assign to each one, this is
certainly perfect, but I was worried about what is happening on the dom0, not
allowing me to see all the free RAM I should see.

>
> So, again, the reason why you're not seeing 7GB of RAM in Dom0 is
> because they're not there! Dom0 is a virtual machine to which you've
> given 1GB of RAM via the cmdline... Having only 1GB of RAM is just doing
> right what you asked for!
Uhm, OK. So all my doubts come from the fact that, when I was using
xen-sources (and not the vanilla (gentoo) sources), I've always seen all the
free RAM correctly. But if you say this, I can be more pacific. ;-)

>
> I can understand that it might look a bit tricky, but what you seem to
> be missing here is you should consider Dom0 pretty much like any other
> VM that Xen is managing as the hypervisor.
Yes, this is clear to me. Thank you for remarking this point anyway.

>
> Hope of being of some help.
For sure yes! I appreciate your interest.

Thank you so much.

Best Regards,

Flavio

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raistlin at linux

May 10, 2012, 10:26 AM

Post #13 of 37 (3330 views)
Permalink
Re: Dom0 Memory? [In reply to]

On Thu, 2012-05-10 at 14:20 +0200, Flavio wrote:
> On 10 May 2012 12:38, Dario Faggioli <raistlin [at] linux> wrote:
> > On Wed, 2012-05-09 at 17:52 +0200, Flavio wrote:
> >> > What does 'xm info' say?
> >> # xl info
> >> total_memory : 8107
> >> free_memory : 6968
> >>
> > So, 8GB of RAM is what Xen knows, ~7 of them being free... What's the
> > problem?
> Yes, but as far as I can see, even if xl info gives me such values,
> the real amount
> of free RAM is very less than it declares. I've reported also the free and the
> cat /proc/meminfo output on the purpose and what I can see, practically, is that
> I cannot run Chromium, or other "big" applications because of this lack of free
> RAM. This is an issue that has been confirmed many months ago.
>
Just to be sure we got each other properly, that is again fine,
as /proc/meminfo or `free' in Dom0 reports the amount of free memory in
Dom0, which is a VM to which you've given 1GB of RAM.

Then, if your Dom0 has issues (slowdowns, OOM killings, etc.) with that
amount of RAM you either should put more memory on dom0_mem= or avoid
putting the dom0_mem option at all. Of course, the wiki links tells you
shouldn't get rid of that cmdline option but, hey, one has to be free to
do what he likes on his machines! :-P

It's not hard to imagine that 1GB (unfortunately) is far less what a
modern Desktop needs to run properly. And about the latter point, if you
install the xen packages on Fedora, it does not give you any dom0_mem
option by default, so...

> Uhm, OK. So all my doubts come from the fact that, when I was using
> xen-sources (and not the vanilla (gentoo) sources), I've always seen all the
> free RAM correctly. But if you say this, I can be more pacific. ;-)
>
That could well be true. I'm hacking on Xen from a very short while, so
I'm not going to claim it has always been like it is now! :-D

> > Hope of being of some help.
> For sure yes! I appreciate your interest.
>
Glad to hear that. :-)

Regards,
Dario

--
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://retis.sssup.it/people/faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)
Attachments: signature.asc (0.19 KB)


fbcyborg at gmail

May 10, 2012, 12:05 PM

Post #14 of 37 (3326 views)
Permalink
Re: Dom0 Memory? [In reply to]

On 10 May 2012 19:26, Dario Faggioli <raistlin [at] linux> wrote:
> Just to be sure we got each other properly, that is again fine,
> as /proc/meminfo or `free' in Dom0 reports the amount of free memory in
> Dom0, which is a VM to which you've given 1GB of RAM.
>
> Then, if your Dom0 has issues (slowdowns, OOM killings, etc.) with that
> amount of RAM you either should put more memory on dom0_mem= or avoid
> putting the dom0_mem option at all.
Well, with regard to this point, I've done many different tests during the last
period actually, just to see how it behaves. I stated that if I give
too much RAM
to dom0, the system is unusable (~3-4GB, or ~7-8 for the laptop). If I
avoid to set
such parameter, the amount of free RAM is random! One time I can get 3 or 4 GB
free (for my desktop PC with 4GB of RAM) or 300MB free, or some other random
value.

> Of course, the wiki links tells you
> shouldn't get rid of that cmdline option but, hey, one has to be free to
> do what he likes on his machines! :-P
LOL, of course! :-)

Best regards,

Flavio

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ray at aarden

May 10, 2012, 4:55 PM

Post #15 of 37 (3376 views)
Permalink
Re: Dom0 Memory? [In reply to]

On Wed, 2012-05-09 at 17:52 +0200, Flavio wrote:
> > What does 'xm info' say?
> # xl info
> total_memory : 8107
> free_memory : 6968
>
So, 8GB of RAM is what Xen knows, ~7 of them being free... What's the
problem?

> As you can see, my 8GB of RAM have disappeared.
> What can you say about that?
>
Uh? :-O

Ok, this might be a bit too technical, but perhaps still of help:
http://blog.xen.org/index.php/2012/04/30/do%EF%BB%BFm0-memory-where-it-has-not-gone/

I'm also sure this has been mentioned in this or another thread related
to this "issue":
http://wiki.xen.org/wiki/Xen_Best_Practices
http://wiki.xen.org/wiki/Xen_Best_Practices#Why_should_I_dedicate_fixed_amount_of_memory_for_Xen_dom0.3F

Also trying to quickly summarize what's happening, no, your memory
_has_not_ disappeared. Actually, it is right there for your VMs to use
it (and xl invocation above shows right that).

With dom0_mem=1G you told Xen that one of your VM (the one that it will
automatically call 'Domain0' and that it will automatically create on
boot) will use 1G of your 8G of RAM. If you now try to create another VM
(say 'VM_1') with 2G of RAM, it will just do that, and you'll have 1G
+2G=3G out of 8G of your RAM dedicated to these two VMs, while the other
5G are still free.

Have you tried that? If you do, try running `xl info' on Dom0 again
after that. Try also SSH-ing in 'VM_1' and asking (e.g., via `free -m')
how many total and free memory it has. As one should expect, it will say
it has 2GB of RAM in total... Does this make sense?

So, again, the reason why you're not seeing 7GB of RAM in Dom0 is
because they're not there! Dom0 is a virtual machine to which you've
given 1GB of RAM via the cmdline... Having only 1GB of RAM is just doing
right what you asked for!

I can understand that it might look a bit tricky, but what you seem to
be missing here is you should consider Dom0 pretty much like any other
VM that Xen is managing as the hypervisor.

Hope of being of some help.

Regards,
Dario
--
Those were interesting articles. I'm left with a couple questions.
1) How does one determine how much memory to allocate?
2) Is there a way to garauntee that dom0 never has to use a page file?
3) Sorry for the unrelated component - That wiki page was great. When
building for the most current version of Xen, what is a good way to find
all the related wiki pages?

Ray



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http://lists.xen.org/xen-users


itobin at tidyhosts

May 11, 2012, 1:11 AM

Post #16 of 37 (3377 views)
Permalink
Re: Dom0 Memory? [In reply to]

Hello,

There is still a bug.

For example I have 16Gb RAM, 512 dedicated to Dom0, 2 Gb dedicated to VM1 which leaves me this amount of RAM

Xl info

total_memory : 15869
free_memory : 13124

this is correct as 512MB is missing because it is assigned to Dom0.

Now I create a new config file for VM2 and I set the RAM

memory = 12288

Now this should be fine and allow me to boot the VM as I should still have a bit of memory left over.

Xl create vm2


libxl: error: libxl.c:2150:libxl_set_memory_target new target 0 for dom0 is below the minimum threshold

libxl: error: libxl.c:2150:libxl_set_memory_target new target 0 for dom0 is below the minimum threshold

libxl: error: libxl.c:2150:libxl_set_memory_target new target 0 for dom0 is below the minimum threshold

failed to free memory for the domain

Why it is trying to take memory from dom0??

Thanks

Ian




-----Original Message-----
From: xen-users-bounces [at] lists [mailto:xen-users-bounces [at] lists] On Behalf Of ray [at] aarden
Sent: 11 May 2012 00:56
To: xen-users [at] lists
Subject: Re: [Xen-users] Dom0 Memory?

On Wed, 2012-05-09 at 17:52 +0200, Flavio wrote:
> > What does 'xm info' say?
> # xl info
> total_memory : 8107
> free_memory : 6968
>
So, 8GB of RAM is what Xen knows, ~7 of them being free... What's the problem?

> As you can see, my 8GB of RAM have disappeared.
> What can you say about that?
>
Uh? :-O

Ok, this might be a bit too technical, but perhaps still of help:
http://blog.xen.org/index.php/2012/04/30/do%EF%BB%BFm0-memory-where-it-has-not-gone/

I'm also sure this has been mentioned in this or another thread related to this "issue":
http://wiki.xen.org/wiki/Xen_Best_Practices
http://wiki.xen.org/wiki/Xen_Best_Practices#Why_should_I_dedicate_fixed_amount_of_memory_for_Xen_dom0.3F

Also trying to quickly summarize what's happening, no, your memory _has_not_ disappeared. Actually, it is right there for your VMs to use it (and xl invocation above shows right that).

With dom0_mem=1G you told Xen that one of your VM (the one that it will automatically call 'Domain0' and that it will automatically create on
boot) will use 1G of your 8G of RAM. If you now try to create another VM (say 'VM_1') with 2G of RAM, it will just do that, and you'll have 1G
+2G=3G out of 8G of your RAM dedicated to these two VMs, while the other
5G are still free.

Have you tried that? If you do, try running `xl info' on Dom0 again after that. Try also SSH-ing in 'VM_1' and asking (e.g., via `free -m') how many total and free memory it has. As one should expect, it will say it has 2GB of RAM in total... Does this make sense?

So, again, the reason why you're not seeing 7GB of RAM in Dom0 is because they're not there! Dom0 is a virtual machine to which you've given 1GB of RAM via the cmdline... Having only 1GB of RAM is just doing right what you asked for!

I can understand that it might look a bit tricky, but what you seem to be missing here is you should consider Dom0 pretty much like any other VM that Xen is managing as the hypervisor.

Hope of being of some help.

Regards,
Dario
--
Those were interesting articles. I'm left with a couple questions.
1) How does one determine how much memory to allocate?
2) Is there a way to garauntee that dom0 never has to use a page file?
3) Sorry for the unrelated component - That wiki page was great. When building for the most current version of Xen, what is a good way to find all the related wiki pages?

Ray



_______________________________________________
Xen-users mailing list
Xen-users [at] lists
http://lists.xen.org/xen-users

_______________________________________________
Xen-users mailing list
Xen-users [at] lists
http://lists.xen.org/xen-users


Ian.Campbell at citrix

May 11, 2012, 1:27 AM

Post #17 of 37 (3354 views)
Permalink
Re: Dom0 Memory? [In reply to]

On Fri, 2012-05-11 at 09:11 +0100, Ian Tobin wrote:
> Hello,
>
> There is still a bug.
>
> For example I have 16Gb RAM, 512 dedicated to Dom0, 2 Gb dedicated to VM1 which leaves me this amount of RAM
>
> Xl info
>
> total_memory : 15869
> free_memory : 13124
>
> this is correct as 512MB is missing because it is assigned to Dom0.
>
> Now I create a new config file for VM2 and I set the RAM
>
> memory = 12288
>
> Now this should be fine and allow me to boot the VM as I should still have a bit of memory left over.
>
> Xl create vm2
>
>
> libxl: error: libxl.c:2150:libxl_set_memory_target new target 0 for dom0 is below the minimum threshold
>
> libxl: error: libxl.c:2150:libxl_set_memory_target new target 0 for dom0 is below the minimum threshold
>
> libxl: error: libxl.c:2150:libxl_set_memory_target new target 0 for dom0 is below the minimum threshold
>
> failed to free memory for the domain
>
> Why it is trying to take memory from dom0??

You need to set "autoballoon=0" in /etc/xen/xl.conf if you don't want xl
to automatically balloon dom0 down when starting a domain -- for example
if you use the dom0_mem option.

Ian.



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itobin at tidyhosts

May 11, 2012, 1:49 AM

Post #18 of 37 (3367 views)
Permalink
Re: Dom0 Memory? [In reply to]

Ian,

You’re a legend! This has been giving me grief for a long time, had no idea of this setting.

Thanks

Ian



-----Original Message-----
From: Ian Campbell [mailto:Ian.Campbell [at] citrix]
Sent: 11 May 2012 09:27
To: Ian Tobin
Cc: ray [at] aarden; xen-users [at] lists
Subject: Re: [Xen-users] Dom0 Memory?

On Fri, 2012-05-11 at 09:11 +0100, Ian Tobin wrote:
> Hello,
>
> There is still a bug.
>
> For example I have 16Gb RAM, 512 dedicated to Dom0, 2 Gb dedicated to
> VM1 which leaves me this amount of RAM
>
> Xl info
>
> total_memory : 15869
> free_memory : 13124
>
> this is correct as 512MB is missing because it is assigned to Dom0.
>
> Now I create a new config file for VM2 and I set the RAM
>
> memory = 12288
>
> Now this should be fine and allow me to boot the VM as I should still have a bit of memory left over.
>
> Xl create vm2
>
>
> libxl: error: libxl.c:2150:libxl_set_memory_target new target 0 for
> dom0 is below the minimum threshold
>
> libxl: error: libxl.c:2150:libxl_set_memory_target new target 0 for
> dom0 is below the minimum threshold
>
> libxl: error: libxl.c:2150:libxl_set_memory_target new target 0 for
> dom0 is below the minimum threshold
>
> failed to free memory for the domain
>
> Why it is trying to take memory from dom0??

You need to set "autoballoon=0" in /etc/xen/xl.conf if you don't want xl to automatically balloon dom0 down when starting a domain -- for example if you use the dom0_mem option.

Ian.



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Ian.Campbell at citrix

May 11, 2012, 2:03 AM

Post #19 of 37 (3327 views)
Permalink
Re: Dom0 Memory? [In reply to]

On Fri, 2012-05-11 at 09:49 +0100, Ian Tobin wrote:
> You’re a legend! This has been giving me grief for a long time, had no
> idea of this setting.

Out of interest where did you see the dom0_mem= recommendation without
mention of the autoballoon setting? We should try and update those which
we can to mention both together...

Ian.


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itobin at tidyhosts

May 11, 2012, 2:07 AM

Post #20 of 37 (3313 views)
Permalink
Re: Dom0 Memory? [In reply to]

It was just something ive always set, but the wiki is out of date

http://wiki.xensource.com/xenwiki/XenBestPractices

at the top it mentions about the autoballooing but no mention of the /etc/xen/xl.conf or to that point any mention of xl at all.

Thanks

Ian



-----Original Message-----
From: Ian Campbell [mailto:Ian.Campbell [at] citrix]
Sent: 11 May 2012 10:04
To: Ian Tobin
Cc: ray [at] aarden; xen-users [at] lists
Subject: RE: [Xen-users] Dom0 Memory?

On Fri, 2012-05-11 at 09:49 +0100, Ian Tobin wrote:
> You’re a legend! This has been giving me grief for a long time, had no
> idea of this setting.

Out of interest where did you see the dom0_mem= recommendation without mention of the autoballoon setting? We should try and update those which we can to mention both together...

Ian.


_______________________________________________
Xen-users mailing list
Xen-users [at] lists
http://lists.xen.org/xen-users


Ian.Campbell at citrix

May 11, 2012, 2:20 AM

Post #21 of 37 (3315 views)
Permalink
Re: Dom0 Memory? [In reply to]

On Fri, 2012-05-11 at 10:07 +0100, Ian Tobin wrote:
> It was just something ive always set, but the wiki is out of date
>
> http://wiki.xensource.com/xenwiki/XenBestPractices
>
> at the top it mentions about the autoballooing but no mention of the /etc/xen/xl.conf or to that point any mention of xl at all.

Thanks, that's actually a static copy of the old wiki, however
http://wiki.xen.org/wiki/XenBestPractices also has the same issue AFAICT
so I'll update that.

Cheers,
Ian.

>
> Thanks
>
> Ian
>
>
>
> -----Original Message-----
> From: Ian Campbell [mailto:Ian.Campbell [at] citrix]
> Sent: 11 May 2012 10:04
> To: Ian Tobin
> Cc: ray [at] aarden; xen-users [at] lists
> Subject: RE: [Xen-users] Dom0 Memory?
>
> On Fri, 2012-05-11 at 09:49 +0100, Ian Tobin wrote:
> > You’re a legend! This has been giving me grief for a long time, had no
> > idea of this setting.
>
> Out of interest where did you see the dom0_mem= recommendation without mention of the autoballoon setting? We should try and update those which we can to mention both together...
>
> Ian.
>
>



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http://lists.xen.org/xen-users


list at fajar

May 11, 2012, 2:35 AM

Post #22 of 37 (3312 views)
Permalink
Re: Dom0 Memory? [In reply to]

On Fri, May 11, 2012 at 3:27 PM, Ian Campbell <Ian.Campbell [at] citrix> wrote:
> On Fri, 2012-05-11 at 09:11 +0100, Ian Tobin wrote:

>> Xl info
>>
>> total_memory : 15869
>> free_memory : 13124


>> Now I create a new config file for VM2 and I set the RAM
>>
>> memory = 12288

>> libxl: error: libxl.c:2150:libxl_set_memory_target new target 0 for dom0 is below the minimum threshold
>>
>> failed to free memory for the domain
>>
>> Why it is trying to take memory from dom0??
>
> You need to set "autoballoon=0" in /etc/xen/xl.conf if you don't want xl
> to automatically balloon dom0 down when starting a domain -- for example
> if you use the dom0_mem option.
>
> Ian.

Isn't that a bug? Shouldn't xl try to use free_memory first, and only
try to baloon-down memory from dom0 if it still needs more?

--
Fajar

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fbcyborg at gmail

May 11, 2012, 3:23 AM

Post #23 of 37 (3314 views)
Permalink
Re: Dom0 Memory? [In reply to]

On 11 May 2012 10:27, Ian Campbell <Ian.Campbell [at] citrix> wrote:
> You need to set "autoballoon=0" in /etc/xen/xl.conf if you don't want xl
> to automatically balloon dom0 down when starting a domain -- for example
> if you use the dom0_mem option.
Wow! Great hint. I dindn't know that too!
Set to 0, immediately.

On 11 May 2012 11:35, Fajar A. Nugraha <list [at] fajar> wrote:
>
> Isn't that a bug? Shouldn't xl try to use free_memory first, and only
> try to baloon-down memory from dom0 if it still needs more?
This is a very good question. What about that?

--
Flavio

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itobin at tidyhosts

May 11, 2012, 3:26 AM

Post #24 of 37 (3308 views)
Permalink
Re: Dom0 Memory? [In reply to]

You may want to mention about the dom0_mem=512M,max:512M

This stops the dom0 memory disappearing

Thanks

Ian

-----Original Message-----
From: Ian Campbell [mailto:Ian.Campbell [at] citrix]
Sent: 11 May 2012 10:20
To: Ian Tobin
Cc: ray [at] aarden; xen-users [at] lists
Subject: RE: [Xen-users] Dom0 Memory?

On Fri, 2012-05-11 at 10:07 +0100, Ian Tobin wrote:
> It was just something ive always set, but the wiki is out of date
>
> http://wiki.xensource.com/xenwiki/XenBestPractices
>
> at the top it mentions about the autoballooing but no mention of the /etc/xen/xl.conf or to that point any mention of xl at all.

Thanks, that's actually a static copy of the old wiki, however http://wiki.xen.org/wiki/XenBestPractices also has the same issue AFAICT so I'll update that.

Cheers,
Ian.

>
> Thanks
>
> Ian
>
>
>
> -----Original Message-----
> From: Ian Campbell [mailto:Ian.Campbell [at] citrix]
> Sent: 11 May 2012 10:04
> To: Ian Tobin
> Cc: ray [at] aarden; xen-users [at] lists
> Subject: RE: [Xen-users] Dom0 Memory?
>
> On Fri, 2012-05-11 at 09:49 +0100, Ian Tobin wrote:
> > You’re a legend! This has been giving me grief for a long time, had
> > no idea of this setting.
>
> Out of interest where did you see the dom0_mem= recommendation without mention of the autoballoon setting? We should try and update those which we can to mention both together...
>
> Ian.
>
>



_______________________________________________
Xen-users mailing list
Xen-users [at] lists
http://lists.xen.org/xen-users


itobin at tidyhosts

May 11, 2012, 3:27 AM

Post #25 of 37 (3364 views)
Permalink
Re: Dom0 Memory? [In reply to]

It does seem to be a bug as it didn't used to happen with xm

Thanks

Ian



-----Original Message-----
From: xen-users-bounces [at] lists [mailto:xen-users-bounces [at] lists] On Behalf Of Fajar A. Nugraha
Sent: 11 May 2012 10:36
To: Ian Campbell
Cc: xen-users [at] lists
Subject: Re: [Xen-users] Dom0 Memory?

On Fri, May 11, 2012 at 3:27 PM, Ian Campbell <Ian.Campbell [at] citrix> wrote:
> On Fri, 2012-05-11 at 09:11 +0100, Ian Tobin wrote:

>> Xl info
>>
>> total_memory : 15869
>> free_memory : 13124


>> Now I create a new config file for VM2 and I set the RAM
>>
>> memory = 12288

>> libxl: error: libxl.c:2150:libxl_set_memory_target new target 0 for
>> dom0 is below the minimum threshold
>>
>> failed to free memory for the domain
>>
>> Why it is trying to take memory from dom0??
>
> You need to set "autoballoon=0" in /etc/xen/xl.conf if you don't want
> xl to automatically balloon dom0 down when starting a domain -- for
> example if you use the dom0_mem option.
>
> Ian.

Isn't that a bug? Shouldn't xl try to use free_memory first, and only try to baloon-down memory from dom0 if it still needs more?

--
Fajar

_______________________________________________
Xen-users mailing list
Xen-users [at] lists
http://lists.xen.org/xen-users



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