Could someone explain why it is recommended to limit the amount of memory on the Dom0 via setting dom0_mem=XXX in grub.conf? Are there situations where the dom0 would grab onto more memory then it needs? I''ve got two systems (RHEL5.1) running with the Xen kernel; each system (X86-64) has 8 GB of RAM. On one system, as reported by "xm list", the dom0 is using 4978 MiB, while the sum of the five domU''s memory usage is 2075 MiB, which roughly equals full usage of the 8 GB. On the other, the dom0 is using 2943 MiB, while the sum of the six domUs is 5114 MiB, again with a rough total of 8 GB. So, it appears that the dom0 basically just consumes all memory not used by domUs, and will release that memory when it is needed by a new guest. If that is true, then I don''t see the advantage of forcing the dom0 to a hard memory limit, but there must be one, since the option is there and people are using it (or so google tells me.) Do I have this wrong, or am I not understanding something? Thanks, -s- _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
---------- Forwarded message ---------- From: Gastón Keller <gastonkeller@gmail.com> Date: Sat, 14 Jun 2008 08:34:56 -0400 Subject: Re: [Xen-users] Why limit dom0''s memory? To: "Sandor W. Sklar" <ssklar@stanford.edu> On 6/14/08, Sandor W. Sklar <ssklar@stanford.edu> wrote:> > Could someone explain why it is recommended to limit the amount of > memory on the Dom0 via setting dom0_mem=XXX in grub.conf? Are there > situations where the dom0 would grab onto more memory then it needs? > > I''ve got two systems (RHEL5.1) running with the Xen kernel; each > system (X86-64) has 8 GB of RAM. > > On one system, as reported by "xm list", the dom0 is using 4978 MiB, > while the sum of the five domU''s memory usage is 2075 MiB, which > roughly equals full usage of the 8 GB. > > On the other, the dom0 is using 2943 MiB, while the sum of the six > domUs is 5114 MiB, again with a rough total of 8 GB. > > So, it appears that the dom0 basically just consumes all memory not > used by domUs, and will release that memory when it is needed by a new > guest. If that is true, then I don''t see the advantage of forcing the > dom0 to a hard memory limit, but there must be one, since the option > is there and people are using it (or so google tells me.) > > Do I have this wrong, or am I not understanding something?AFAIK what some people is doing is setting a level of memory for Dom0 for it to never go down that level (giving memory to the guests). That is, if you set the memory to 1 GB, Dom0 will allocate all your memory except for that 1 GB. It''s a way of ensuring that Dom0 will never run out of memory. Gaston> > Thanks, > -s- > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users >-- La única verdad es la realidad. -- La única verdad es la realidad. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Jun 14, 2008, at 5:35 AM, Gastón Keller wrote:>> I have this wrong, or am I not understanding something? > > AFAIK what some people is doing is setting a level of memory for Dom0 > for it to never go down that level (giving memory to the guests). That > is, if you set the memory to 1 GB, Dom0 will allocate all your memory > except for that 1 GB. It''s a way of ensuring that Dom0 will never run > out of memory.Ah, thanks! That makes sense. Is there some formula for determining how much memory a dom0 might need, given a system with X amount of RAM, and X number of guests? -s- _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Sat, Jun 14, 2008 at 11:47 AM, Sandor W. Sklar <ssklar@stanford.edu> wrote:> > On Jun 14, 2008, at 5:35 AM, Gastón Keller wrote: > >>> I have this wrong, or am I not understanding something? >> >> AFAIK what some people is doing is setting a level of memory for Dom0 >> for it to never go down that level (giving memory to the guests). That >> is, if you set the memory to 1 GB, Dom0 will allocate all your memory >> except for that 1 GB. It''s a way of ensuring that Dom0 will never run >> out of memory. > > Ah, thanks! That makes sense. Is there some formula for determining how > much memory a dom0 might need, given a system with X amount of RAM, and X > number of guests?I wouldn''t know what to tell you. Sorry! =) Gaston> > -s- >-- La única verdad es la realidad. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Sat, Jun 14, 2008 at 11:58 AM, Gastón Keller <gastonkeller@gmail.com> wrote:> On Sat, Jun 14, 2008 at 11:47 AM, Sandor W. Sklar <ssklar@stanford.edu> > wrote: > > > > On Jun 14, 2008, at 5:35 AM, Gastón Keller wrote: > > > >>> I have this wrong, or am I not understanding something? > >> > >> AFAIK what some people is doing is setting a level of memory for Dom0 > >> for it to never go down that level (giving memory to the guests). That > >> is, if you set the memory to 1 GB, Dom0 will allocate all your memory > >> except for that 1 GB. It''s a way of ensuring that Dom0 will never run > >> out of memory. > > > > Ah, thanks! That makes sense. Is there some formula for determining how > > much memory a dom0 might need, given a system with X amount of RAM, and X > > number of guests? > > I wouldn''t know what to tell you. Sorry! =) >I don''t think there is a magic formula like that anyway. It will depend on what you are using the system for. You should try to minimize what is run in dom0. You should make sure that your guests have sufficient memory so that they are not thrashing the disk. All this depends on the load your system is going to take on. Bottom line is that not running out of memory on Dom0 is first priority, then guests. Always try to give some wiggle room if possible and do lots of testing if you can. For more information on Xen in book format, take a look at "Running Xen: A Hands-on Guide to the Art of Virtualization" (http://runningxen.com) Cheers, Todd _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Sandor W. Sklar wrote:> > On Jun 14, 2008, at 5:35 AM, Gastón Keller wrote: > >>> I have this wrong, or am I not understanding something? >> >> AFAIK what some people is doing is setting a level of memory for Dom0 >> for it to never go down that level (giving memory to the guests). That >> is, if you set the memory to 1 GB, Dom0 will allocate all your memory >> except for that 1 GB. It''s a way of ensuring that Dom0 will never run >> out of memory. > > Ah, thanks! That makes sense. Is there some formula for determining > how much memory a dom0 might need, given a system with X amount of > RAM, and X number of guests? > > -s-The "formula" would largely depend on what you''re going to run on dom0, and is roughly the same as for a domU instance. On a VPS server, which only serves domU VPS, you probably won''t need more than 512MB RAM. All our VPS servers run min. 512MB RAM, which is enough for SSH, FTP, exim, Squid, syslogd, etc to run. All the other services (MySQL, Apache, PostgreSQL, etc) are run from the domU VPShth -- Kind Regards Rudi Ahlers CEO, SoftDux Web: http://www.SoftDux.com Check out my technical blog, http://blog.softdux.com for Linux or other technical stuff, or visit http://www.WebHostingTalk.co.za for Web Hosting stuff _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Jun 14, 2008, at 11:48 AM, Rudi Ahlers wrote:> Sandor W. Sklar wrote: >> >> On Jun 14, 2008, at 5:35 AM, Gastón Keller wrote: >> >>>> I have this wrong, or am I not understanding something? >>> >>> AFAIK what some people is doing is setting a level of memory for >>> Dom0 >>> for it to never go down that level (giving memory to the guests). >>> That >>> is, if you set the memory to 1 GB, Dom0 will allocate all your >>> memory >>> except for that 1 GB. It''s a way of ensuring that Dom0 will never >>> run >>> out of memory. >> >> Ah, thanks! That makes sense. Is there some formula for >> determining how much memory a dom0 might need, given a system with >> X amount of RAM, and X number of guests? >> >> -s- > The "formula" would largely depend on what you''re going to run on > dom0, and is roughly the same as for a domU instance. On a VPS > server, which only serves domU VPS, you probably won''t need more > than 512MB RAM. All our VPS servers run min. 512MB RAM, which is > enough for SSH, FTP, exim, Squid, syslogd, etc to run. All the other > services (MySQL, Apache, PostgreSQL, etc) are run from the domU VPShthWell, of course, the amount of memory that a dom0 needs depends upon the service running within it. I guess I didn''t word my question explicitly enough. Is there a formula for determine how much memory a dom0 might need, given a system with X amount of RAM, and X number of guests, assuming there are no other services running in the dom0? Thanks, -s- _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Sun, 2008-06-15 at 17:45 -0700, Sandor W. Sklar wrote:> Well, of course, the amount of memory that a dom0 needs depends upon > the service running within it. I guess I didn''t word my question > explicitly enough. Is there a formula for determine how much memory a > dom0 might need, given a system with X amount of RAM, and X number of > guests, assuming there are no other services running in the dom0?You are hoping to calculate the best possible density? I.e. give dom-0 xx MB per pv guest, xx MB per HVM guest? Even that is too broad to really pin down, it would really depend on what you give the guests and how much they exercise the disks. Regards, --Tim _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Jun 15, 2008, at 7:37 PM, Tim Post wrote:> On Sun, 2008-06-15 at 17:45 -0700, Sandor W. Sklar wrote: >> Well, of course, the amount of memory that a dom0 needs depends upon >> the service running within it. I guess I didn''t word my question >> explicitly enough. Is there a formula for determine how much >> memory a >> dom0 might need, given a system with X amount of RAM, and X number of >> guests, assuming there are no other services running in the dom0? > > You are hoping to calculate the best possible density? I.e. give dom-0 > xx MB per pv guest, xx MB per HVM guest?Indeed, exactly! Not exact numbers, but a guideline that would let me maximize the memory available to guests without running the risk of starving the dom0.> Even that is too broad to really pin down, it would really depend on > what you give the guests and how much they exercise the disks.OK, thanks, I guess I assumed as much, given that if such information existed, Google would have told me. :-) -s- _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
2008/6/14 Gastón Keller <gastonkeller@gmail.com>:> ---------- Forwarded message ---------- > From: Gastón Keller <gastonkeller@gmail.com> > Date: Sat, 14 Jun 2008 08:34:56 -0400 > Subject: Re: [Xen-users] Why limit dom0''s memory? > To: "Sandor W. Sklar" <ssklar@stanford.edu> > > On 6/14/08, Sandor W. Sklar <ssklar@stanford.edu> wrote: > > > > Could someone explain why it is recommended to limit the amount of > > memory on the Dom0 via setting dom0_mem=XXX in grub.conf? Are there > > situations where the dom0 would grab onto more memory then it needs? >Here the reason we set the "dom0_mem" in grub.conf is very precise : without it the 12 domUs autostarted have problems at startup, looked like the dom0 had not time enough to correctly ballon out memory for domUs. By setting in advance the dom0 memory, no more problem (note that the problem occured only when a lot of domUs are created simultaneously).> > AFAIK what some people is doing is setting a level of memory for Dom0 > for it to never go down that level (giving memory to the guests). That > is, if you set the memory to 1 GB, Dom0 will allocate all your memory > except for that 1 GB. It''s a way of ensuring that Dom0 will never run > out of memory.I don''t think so. The minimum memory for dom0 is defined through the "dom0_min_mem" parameter in the xend-config.sxp file.> > > Gaston > > > > Thanks, > > -s- > > > > > > _______________________________________________ > > Xen-users mailing list > > Xen-users@lists.xensource.com > > http://lists.xensource.com/xen-users > > > > > -- > La única verdad es la realidad. > > > > -- > La única verdad es la realidad. > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> > So, it appears that the dom0 basically just consumes all memory not > > used by domUs, and will release that memory when it is needed by a new > > guest. If that is true, then I don''t see the advantage of forcing the > > dom0 to a hard memory limit, but there must be one, since the option > > is there and people are using it (or so google tells me.) > > > > Do I have this wrong, or am I not understanding something? > > AFAIK what some people is doing is setting a level of memory for Dom0 > for it to never go down that level (giving memory to the guests). That > is, if you set the memory to 1 GB, Dom0 will allocate all your memory > except for that 1 GB. It''s a way of ensuring that Dom0 will never run > out of memory.More information / clarification: The dom0_mem parameter on the Xen command line is used to set how much memory dom0 is allocated when the system starts. This is instead of it being given all free memory in the system. By default, dom0 shrinks itself as required to free up space for domUs that the administrator starts. Setting dom0_mem does not stop dom0 from shrinking itself below the size in dom0_mem later on in order to accommodate guests, for instance if you start more than anticipated. All it means is that dom0 may not have to immediately shrink to make space for guests, since its not using all the memory to start with. The parameter dom0-min-mem in /etc/xen/xend-config.sxp is used to set the smallest size dom0 will shrink itself to in order to accommodate domUs. Setting it to 0 disables auto-ballooning so that dom0 won''t shrink itself automatically at all. A number of people have had problems with the autoballooning behaviour, since in some cases in the past ballooning dom0 down significantly has caused instability. Starting dom0 up at the right size to begin with is, for various reasons, *not* equivalent to starting it up with all memory and resizing it later. Heavy resizing confused Linux sometimes and made things break. Setting dom0_mem and disabling autoballooning eliminated instability for some in these situations. I''m not clear whether such instabilities are so common now but I still recommend that if you know what size you want dom0 to be you may as well set dom0_mem leave it there! Cheers, Mark -- Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/) _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
That said, I think many people find that for a minimal dom0, not doing much other work about 256MB is a reasonable amount of memory. Maybe you''d want to go to 512MB if you had many guests and / or memory to spare. dom0''s requirements aren''t extravagent, as long as you''re not running loads of things in it (which on a server you shouldn''t, for security reasons). Of course if you start running X and a modern desktop, you can expect dom0 to have significantly higher memory requirements, just as a normal machine would ;-) Cheers, Mark On Monday 16 June 2008, Sandor W. Sklar wrote:> On Jun 15, 2008, at 7:37 PM, Tim Post wrote: > > On Sun, 2008-06-15 at 17:45 -0700, Sandor W. Sklar wrote: > >> Well, of course, the amount of memory that a dom0 needs depends upon > >> the service running within it. I guess I didn''t word my question > >> explicitly enough. Is there a formula for determine how much > >> memory a > >> dom0 might need, given a system with X amount of RAM, and X number of > >> guests, assuming there are no other services running in the dom0? > > > > You are hoping to calculate the best possible density? I.e. give dom-0 > > xx MB per pv guest, xx MB per HVM guest? > > Indeed, exactly! Not exact numbers, but a guideline that would let me > maximize the memory available to guests without running the risk of > starving the dom0. > > > Even that is too broad to really pin down, it would really depend on > > what you give the guests and how much they exercise the disks. > > OK, thanks, I guess I assumed as much, given that if such information > existed, Google would have told me. :-) > > -s- > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users-- Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/) _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Hi,
It''s strange for me.
I''ve got 8Go of RAM.
I''ve defined 1024M to Dom0 on the boot (/boot/grub/menu.lst)
...
kernel /xen-3.1.0.gz dom0_mem=1024M console=vga
...
I''ve got some Guests with some Go of RAM et it still remain a lot of
RAM to use that i attibue to the news guests.
But the problem that when i tried to create it, i had this error:
# xm create toto.cfg
Using config file "/etc/xen/toto.cfg".
Error: I need 1073152 KiB, but dom0_min_mem is 200704 and shrinking to
200704 KiB would leave only 675672 KiB free.
# cat /etc/xen/toto.cfg
---
memory = ''1048''
---
If i shutdown one of my other guest, it will ok.
It''s strange since i defined 1Go to Dom0, i get only 853Mo
# free -mo
total used free shared buffers cached
Mem: 853 190 662 0 23 32
Would someone explain me about this?
i''m with Debian Etch, Xen 3.1, 8Go RAM.
Thank you in advance.
On Thu, Jun 19, 2008 at 4:24 AM, Mark Williamson
<mark.williamson@cl.cam.ac.uk> wrote:> That said, I think many people find that for a minimal dom0, not doing much
> other work about 256MB is a reasonable amount of memory. Maybe
you''d want to
> go to 512MB if you had many guests and / or memory to spare.
dom0''s
> requirements aren''t extravagent, as long as you''re not
running loads of
> things in it (which on a server you shouldn''t, for security
reasons).
>
> Of course if you start running X and a modern desktop, you can expect dom0
to
> have significantly higher memory requirements, just as a normal machine
> would ;-)
>
> Cheers,
> Mark
>
> On Monday 16 June 2008, Sandor W. Sklar wrote:
>> On Jun 15, 2008, at 7:37 PM, Tim Post wrote:
>> > On Sun, 2008-06-15 at 17:45 -0700, Sandor W. Sklar wrote:
>> >> Well, of course, the amount of memory that a dom0 needs
depends upon
>> >> the service running within it. I guess I didn''t word
my question
>> >> explicitly enough. Is there a formula for determine how much
>> >> memory a
>> >> dom0 might need, given a system with X amount of RAM, and X
number of
>> >> guests, assuming there are no other services running in the
dom0?
>> >
>> > You are hoping to calculate the best possible density? I.e. give
dom-0
>> > xx MB per pv guest, xx MB per HVM guest?
>>
>> Indeed, exactly! Not exact numbers, but a guideline that would let me
>> maximize the memory available to guests without running the risk of
>> starving the dom0.
>>
>> > Even that is too broad to really pin down, it would really depend
on
>> > what you give the guests and how much they exercise the disks.
>>
>> OK, thanks, I guess I assumed as much, given that if such information
>> existed, Google would have told me. :-)
>>
>> -s-
>>
>>
>> _______________________________________________
>> Xen-users mailing list
>> Xen-users@lists.xensource.com
>> http://lists.xensource.com/xen-users
>
>
>
> --
> Push Me Pull You - Distributed SCM tool
(http://www.cl.cam.ac.uk/~maw48/pmpu/)
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users
>
_______________________________________________
Xen-users mailing list
Xen-users@lists.xensource.com
http://lists.xensource.com/xen-users
Hi there,> It''s strange for me. > I''ve got 8Go of RAM. > I''ve defined 1024M to Dom0 on the boot (/boot/grub/menu.lst) > ... > kernel /xen-3.1.0.gz dom0_mem=1024M console=vga > ... > > I''ve got some Guests with some Go of RAM et it still remain a lot of > RAM to use that i attibue to the news guests. > But the problem that when i tried to create it, i had this error: > > # xm create toto.cfg > Using config file "/etc/xen/toto.cfg". > Error: I need 1073152 KiB, but dom0_min_mem is 200704 and shrinking to > 200704 KiB would leave only 675672 KiB free. > > # cat /etc/xen/toto.cfg > --- > memory = ''1048'' > --- > > If i shutdown one of my other guest, it will ok. > It''s strange since i defined 1Go to Dom0, i get only 853Mo > # free -mo > > total used free shared buffers cached > Mem: 853 190 662 0 23 32 > > > Would someone explain me about this? > i''m with Debian Etch, Xen 3.1, 8Go RAM.Is that "free" output from when dom0 is freshly booted, or after you''ve started some domains? Although you''re setting dom0_mem=1024M, which means dom0 *initially* has 1GB of RAM, it looks like your dom0-min-mem setting in /etc/xen/xend-config.sxp is set to 200704, which will permit dom0 to shrink in order to accommodate starting other domains. If dom0 has already shrunk then the value given by "free" will be correspondingly reduced. The error messages you''re seeing are due to dom0 not being able to shrink enough to accommodate your new domain, suggesting that you''re running short on RAM. xm info can be used to find out the total amount of memory that''s free for Xen to allocate without dom0 needing to shrink. Cheers, Mark> Thank you in advance. > > On Thu, Jun 19, 2008 at 4:24 AM, Mark Williamson > > <mark.williamson@cl.cam.ac.uk> wrote: > > That said, I think many people find that for a minimal dom0, not doing > > much other work about 256MB is a reasonable amount of memory. Maybe > > you''d want to go to 512MB if you had many guests and / or memory to > > spare. dom0''s requirements aren''t extravagent, as long as you''re not > > running loads of things in it (which on a server you shouldn''t, for > > security reasons). > > > > Of course if you start running X and a modern desktop, you can expect > > dom0 to have significantly higher memory requirements, just as a normal > > machine would ;-) > > > > Cheers, > > Mark > > > > On Monday 16 June 2008, Sandor W. Sklar wrote: > >> On Jun 15, 2008, at 7:37 PM, Tim Post wrote: > >> > On Sun, 2008-06-15 at 17:45 -0700, Sandor W. Sklar wrote: > >> >> Well, of course, the amount of memory that a dom0 needs depends upon > >> >> the service running within it. I guess I didn''t word my question > >> >> explicitly enough. Is there a formula for determine how much > >> >> memory a > >> >> dom0 might need, given a system with X amount of RAM, and X number of > >> >> guests, assuming there are no other services running in the dom0? > >> > > >> > You are hoping to calculate the best possible density? I.e. give dom-0 > >> > xx MB per pv guest, xx MB per HVM guest? > >> > >> Indeed, exactly! Not exact numbers, but a guideline that would let me > >> maximize the memory available to guests without running the risk of > >> starving the dom0. > >> > >> > Even that is too broad to really pin down, it would really depend on > >> > what you give the guests and how much they exercise the disks. > >> > >> OK, thanks, I guess I assumed as much, given that if such information > >> existed, Google would have told me. :-) > >> > >> -s- > >> > >> > >> _______________________________________________ > >> Xen-users mailing list > >> Xen-users@lists.xensource.com > >> http://lists.xensource.com/xen-users > > > > -- > > Push Me Pull You - Distributed SCM tool > > (http://www.cl.cam.ac.uk/~maw48/pmpu/) > > > > _______________________________________________ > > Xen-users mailing list > > Xen-users@lists.xensource.com > > http://lists.xensource.com/xen-users > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users-- Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/) _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Oups!!! total_memory : 3322 while i have 8Go of RAM... i did installed a Debian i686 on a x86_64 Server. It should not be a problem, isn''t it? If i save all my guests, and install again my Xen Server with Debian x86_64 instead of i686, then i restore the guests, will there be a problem? root@gaia: ~ # xm info host : gaia release : 2.6.18-xen version : #1 SMP Fri May 18 16:11:33 BST 2007 machine : i686 nr_cpus : 4 nr_nodes : 1 sockets_per_node : 1 cores_per_socket : 4 threads_per_core : 1 cpu_mhz : 2660 hw_caps : bfebfbff:20100000:00000000:00000040:000ce3bd:00000000:00000001 total_memory : 3322 free_memory : 2 xen_major : 3 xen_minor : 1 xen_extra : .0 xen_caps : xen-3.0-x86_32 hvm-3.0-x86_32 xen_scheduler : credit xen_pagesize : 4096 platform_params : virt_start=0xfc000000 xen_changeset : Fri May 18 15:52:14 2007 +0100 15042:50fe1a769660 cc_compiler : gcc version 3.4.4 20050314 (prerelease) (Debian 3.4.3-13) cc_compile_by : shand cc_compile_domain : localdomain cc_compile_date : Fri May 18 15:53:15 BST 2007 xend_config_format : 4 On Thu, Jun 19, 2008 at 3:56 PM, Mark Williamson <mark.williamson@cl.cam.ac.uk> wrote:> Hi there, > >> It''s strange for me. >> I''ve got 8Go of RAM. >> I''ve defined 1024M to Dom0 on the boot (/boot/grub/menu.lst) >> ... >> kernel /xen-3.1.0.gz dom0_mem=1024M console=vga >> ... >> >> I''ve got some Guests with some Go of RAM et it still remain a lot of >> RAM to use that i attibue to the news guests. >> But the problem that when i tried to create it, i had this error: >> >> # xm create toto.cfg >> Using config file "/etc/xen/toto.cfg". >> Error: I need 1073152 KiB, but dom0_min_mem is 200704 and shrinking to >> 200704 KiB would leave only 675672 KiB free. >> >> # cat /etc/xen/toto.cfg >> --- >> memory = ''1048'' >> --- >> >> If i shutdown one of my other guest, it will ok. >> It''s strange since i defined 1Go to Dom0, i get only 853Mo >> # free -mo >> >> total used free shared buffers cached >> Mem: 853 190 662 0 23 32 >> >> >> Would someone explain me about this? >> i''m with Debian Etch, Xen 3.1, 8Go RAM. > > Is that "free" output from when dom0 is freshly booted, or after you''ve > started some domains? > > Although you''re setting dom0_mem=1024M, which means dom0 *initially* has 1GB > of RAM, it looks like your dom0-min-mem setting in /etc/xen/xend-config.sxp > is set to 200704, which will permit dom0 to shrink in order to accommodate > starting other domains. If dom0 has already shrunk then the value given > by "free" will be correspondingly reduced. > > The error messages you''re seeing are due to dom0 not being able to shrink > enough to accommodate your new domain, suggesting that you''re running short > on RAM. > > xm info can be used to find out the total amount of memory that''s free for Xen > to allocate without dom0 needing to shrink. > > Cheers, > Mark > >> Thank you in advance. >> >> On Thu, Jun 19, 2008 at 4:24 AM, Mark Williamson >> >> <mark.williamson@cl.cam.ac.uk> wrote: >> > That said, I think many people find that for a minimal dom0, not doing >> > much other work about 256MB is a reasonable amount of memory. Maybe >> > you''d want to go to 512MB if you had many guests and / or memory to >> > spare. dom0''s requirements aren''t extravagent, as long as you''re not >> > running loads of things in it (which on a server you shouldn''t, for >> > security reasons). >> > >> > Of course if you start running X and a modern desktop, you can expect >> > dom0 to have significantly higher memory requirements, just as a normal >> > machine would ;-) >> > >> > Cheers, >> > Mark >> > >> > On Monday 16 June 2008, Sandor W. Sklar wrote: >> >> On Jun 15, 2008, at 7:37 PM, Tim Post wrote: >> >> > On Sun, 2008-06-15 at 17:45 -0700, Sandor W. Sklar wrote: >> >> >> Well, of course, the amount of memory that a dom0 needs depends upon >> >> >> the service running within it. I guess I didn''t word my question >> >> >> explicitly enough. Is there a formula for determine how much >> >> >> memory a >> >> >> dom0 might need, given a system with X amount of RAM, and X number of >> >> >> guests, assuming there are no other services running in the dom0? >> >> > >> >> > You are hoping to calculate the best possible density? I.e. give dom-0 >> >> > xx MB per pv guest, xx MB per HVM guest? >> >> >> >> Indeed, exactly! Not exact numbers, but a guideline that would let me >> >> maximize the memory available to guests without running the risk of >> >> starving the dom0. >> >> >> >> > Even that is too broad to really pin down, it would really depend on >> >> > what you give the guests and how much they exercise the disks. >> >> >> >> OK, thanks, I guess I assumed as much, given that if such information >> >> existed, Google would have told me. :-) >> >> >> >> -s- >> >> >> >> >> >> _______________________________________________ >> >> Xen-users mailing list >> >> Xen-users@lists.xensource.com >> >> http://lists.xensource.com/xen-users >> > >> > -- >> > Push Me Pull You - Distributed SCM tool >> > (http://www.cl.cam.ac.uk/~maw48/pmpu/) >> > >> > _______________________________________________ >> > Xen-users mailing list >> > Xen-users@lists.xensource.com >> > http://lists.xensource.com/xen-users >> >> _______________________________________________ >> Xen-users mailing list >> Xen-users@lists.xensource.com >> http://lists.xensource.com/xen-users > > > > -- > Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/) >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> Oups!!! > total_memory : 3322 > > while i have 8Go of RAM... > > i did installed a Debian i686 on a x86_64 Server. It should not be a > problem, isn''t it?You''ve not got PAE support in your Xen / XenLinux; you need that for > 4GB on i686. If you can find Debian Xen and XenLinux images that support PAE (that''s CONFIG_HIGHMEM_64G in the Linux configurator, by the way) then your existing install should support all the memory.> If i save all my guests, and install again my Xen Server with Debian > x86_64 instead of i686, then i restore the guests, will there be a > problem?As in xm save them? I''m not sure if the suspend images will work on x86_64 or not - I''ve never tried / checked. But you should be able to boot 32-bit guests on x86_64 /as long as you have a new enough Xen/. I don''t know what XEn version Debian will be running. The guests *still* need to be PAE for that to work, so I suggest you investigate that route on your existing system first. If you set up 32-bit PAE and then want 64-bit guests later, you can use a 64-bit Xen with a 32-bit dom0 and that will work /as long as you have a new enough Xen and XenLinux/. Hope that helps some. Cheers, Mark> > > > root@gaia: ~ # xm info > host : gaia > release : 2.6.18-xen > version : #1 SMP Fri May 18 16:11:33 BST 2007 > machine : i686 > nr_cpus : 4 > nr_nodes : 1 > sockets_per_node : 1 > cores_per_socket : 4 > threads_per_core : 1 > cpu_mhz : 2660 > hw_caps : > bfebfbff:20100000:00000000:00000040:000ce3bd:00000000:00000001 > total_memory : 3322 > free_memory : 2 > xen_major : 3 > xen_minor : 1 > xen_extra : .0 > xen_caps : xen-3.0-x86_32 hvm-3.0-x86_32 > xen_scheduler : credit > xen_pagesize : 4096 > platform_params : virt_start=0xfc000000 > xen_changeset : Fri May 18 15:52:14 2007 +0100 15042:50fe1a769660 > cc_compiler : gcc version 3.4.4 20050314 (prerelease) > (Debian 3.4.3-13) > cc_compile_by : shand > cc_compile_domain : localdomain > cc_compile_date : Fri May 18 15:53:15 BST 2007 > xend_config_format : 4 > > > > > > > On Thu, Jun 19, 2008 at 3:56 PM, Mark Williamson > > <mark.williamson@cl.cam.ac.uk> wrote: > > Hi there, > > > >> It''s strange for me. > >> I''ve got 8Go of RAM. > >> I''ve defined 1024M to Dom0 on the boot (/boot/grub/menu.lst) > >> ... > >> kernel /xen-3.1.0.gz dom0_mem=1024M console=vga > >> ... > >> > >> I''ve got some Guests with some Go of RAM et it still remain a lot of > >> RAM to use that i attibue to the news guests. > >> But the problem that when i tried to create it, i had this error: > >> > >> # xm create toto.cfg > >> Using config file "/etc/xen/toto.cfg". > >> Error: I need 1073152 KiB, but dom0_min_mem is 200704 and shrinking to > >> 200704 KiB would leave only 675672 KiB free. > >> > >> # cat /etc/xen/toto.cfg > >> --- > >> memory = ''1048'' > >> --- > >> > >> If i shutdown one of my other guest, it will ok. > >> It''s strange since i defined 1Go to Dom0, i get only 853Mo > >> # free -mo > >> > >> total used free shared buffers > >> cached Mem: 853 190 662 0 23 > >> 32 > >> > >> > >> Would someone explain me about this? > >> i''m with Debian Etch, Xen 3.1, 8Go RAM. > > > > Is that "free" output from when dom0 is freshly booted, or after you''ve > > started some domains? > > > > Although you''re setting dom0_mem=1024M, which means dom0 *initially* has > > 1GB of RAM, it looks like your dom0-min-mem setting in > > /etc/xen/xend-config.sxp is set to 200704, which will permit dom0 to > > shrink in order to accommodate starting other domains. If dom0 has > > already shrunk then the value given by "free" will be correspondingly > > reduced. > > > > The error messages you''re seeing are due to dom0 not being able to shrink > > enough to accommodate your new domain, suggesting that you''re running > > short on RAM. > > > > xm info can be used to find out the total amount of memory that''s free > > for Xen to allocate without dom0 needing to shrink. > > > > Cheers, > > Mark > > > >> Thank you in advance. > >> > >> On Thu, Jun 19, 2008 at 4:24 AM, Mark Williamson > >> > >> <mark.williamson@cl.cam.ac.uk> wrote: > >> > That said, I think many people find that for a minimal dom0, not doing > >> > much other work about 256MB is a reasonable amount of memory. Maybe > >> > you''d want to go to 512MB if you had many guests and / or memory to > >> > spare. dom0''s requirements aren''t extravagent, as long as you''re not > >> > running loads of things in it (which on a server you shouldn''t, for > >> > security reasons). > >> > > >> > Of course if you start running X and a modern desktop, you can expect > >> > dom0 to have significantly higher memory requirements, just as a > >> > normal machine would ;-) > >> > > >> > Cheers, > >> > Mark > >> > > >> > On Monday 16 June 2008, Sandor W. Sklar wrote: > >> >> On Jun 15, 2008, at 7:37 PM, Tim Post wrote: > >> >> > On Sun, 2008-06-15 at 17:45 -0700, Sandor W. Sklar wrote: > >> >> >> Well, of course, the amount of memory that a dom0 needs depends > >> >> >> upon the service running within it. I guess I didn''t word my > >> >> >> question explicitly enough. Is there a formula for determine how > >> >> >> much memory a > >> >> >> dom0 might need, given a system with X amount of RAM, and X number > >> >> >> of guests, assuming there are no other services running in the > >> >> >> dom0? > >> >> > > >> >> > You are hoping to calculate the best possible density? I.e. give > >> >> > dom-0 xx MB per pv guest, xx MB per HVM guest? > >> >> > >> >> Indeed, exactly! Not exact numbers, but a guideline that would let > >> >> me maximize the memory available to guests without running the risk > >> >> of starving the dom0. > >> >> > >> >> > Even that is too broad to really pin down, it would really depend > >> >> > on what you give the guests and how much they exercise the disks. > >> >> > >> >> OK, thanks, I guess I assumed as much, given that if such information > >> >> existed, Google would have told me. :-) > >> >> > >> >> -s- > >> >> > >> >> > >> >> _______________________________________________ > >> >> Xen-users mailing list > >> >> Xen-users@lists.xensource.com > >> >> http://lists.xensource.com/xen-users > >> > > >> > -- > >> > Push Me Pull You - Distributed SCM tool > >> > (http://www.cl.cam.ac.uk/~maw48/pmpu/) > >> > > >> > _______________________________________________ > >> > Xen-users mailing list > >> > Xen-users@lists.xensource.com > >> > http://lists.xensource.com/xen-users > >> > >> _______________________________________________ > >> Xen-users mailing list > >> Xen-users@lists.xensource.com > >> http://lists.xensource.com/xen-users > > > > -- > > Push Me Pull You - Distributed SCM tool > > (http://www.cl.cam.ac.uk/~maw48/pmpu/)-- Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/) _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users