I¹m sure this has been asked a bazillion times on this list, but I couldn¹t find a definitive answer: 4GB ram, 3 domU¹s I boot each domU up with 1GB ram, then mem-max and mem-set them to 2GB (which obviously exceeds physical memory limit). They all grow to 2048. It seems that you won¹t see the memory hit 2gb on a domU until it has eaten up more than what it initially booted with, which is fine. The question I have is what would happen if all three domU¹s tried using 2GB? Thanks, BJ Badyk _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> -----Original Message----- > From: xen-users-bounces@lists.xensource.com > [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of > Badyk, Benjamin > Sent: 02 October 2006 16:56 > To: xen-users@lists.xensource.com > Subject: [Xen-users] Memory allocation > > I¹m sure this has been asked a bazillion times on this list, > but I couldn¹t > find a definitive answer: > > 4GB ram, 3 domU¹s > > I boot each domU up with 1GB ram, then mem-max and mem-set them to 2GB > (which obviously exceeds physical memory limit). They all > grow to 2048. It > seems that you won¹t see the memory hit 2gb on a domU until > it has eaten up > more than what it initially booted with, which is fine. The > question I have > is what would happen if all three domU¹s tried using 2GB?If this actually works in the latest (unstable) release of Xen, I suggest you report a bug. Something will go horribly wrong if you have 3 domU''s using 6GB of RAM on a machine with 4GB or actual memory - it should not be possible to set it like that. Xen doesn''t support "swapping" or in other ways overcommitting memory within the domain memory allocation, so somewhere, you''ll have allocated the same memory to more than one domain [assuming "xm list" shows all three domains to have 2GB of RAM each] - which would obviously not work right... But I seem to remember someone sending patches for "sanity checking mem-set", so it may be that it''s fixed in the latest version. I can certainly guarantee that the one or more domains will crash and/or corrupt themselves if you succeed in setting 2GB each for 3 domU''s on a 4GB machine... [Not to mention that dom0 needs some memory, as does Xen itself - even if it''s only some small measures of memory...] -- Mats> > Thanks, > > BJ Badyk > > _______________________________________________ > 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
Hey Mats, thanks for your help. I am actually able to set them beyond the physical ram limit after they''ve been booted, eeek! xenbox## xm list Name ID Mem(MiB) VCPUs State Time(s) Domain-0 0 230 4 r----- 815.1 vm01 25 2048 2 -b---- 10733.4 vm02 26 2048 2 -b---- 306.3 vm03 27 2048 2 -b---- 305.0 On 10/2/06 11:09 AM, "Petersson, Mats" <Mats.Petersson@amd.com> wrote:> > >> -----Original Message----- >> From: xen-users-bounces@lists.xensource.com >> [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of >> Badyk, Benjamin >> Sent: 02 October 2006 16:56 >> To: xen-users@lists.xensource.com >> Subject: [Xen-users] Memory allocation >> >> I¹m sure this has been asked a bazillion times on this list, >> but I couldn¹t >> find a definitive answer: >> >> 4GB ram, 3 domU¹s >> >> I boot each domU up with 1GB ram, then mem-max and mem-set them to 2GB >> (which obviously exceeds physical memory limit). They all >> grow to 2048. It >> seems that you won¹t see the memory hit 2gb on a domU until >> it has eaten up >> more than what it initially booted with, which is fine. The >> question I have >> is what would happen if all three domU¹s tried using 2GB? > > If this actually works in the latest (unstable) release of Xen, I suggest you > report a bug. > > Something will go horribly wrong if you have 3 domU''s using 6GB of RAM on a > machine with 4GB or actual memory - it should not be possible to set it like > that. > > Xen doesn''t support "swapping" or in other ways overcommitting memory within > the domain memory allocation, so somewhere, you''ll have allocated the same > memory to more than one domain [assuming "xm list" shows all three domains to > have 2GB of RAM each] - which would obviously not work right... But I seem to > remember someone sending patches for "sanity checking mem-set", so it may be > that it''s fixed in the latest version. > > I can certainly guarantee that the one or more domains will crash and/or > corrupt themselves if you succeed in setting 2GB each for 3 domU''s on a 4GB > machine... [Not to mention that dom0 needs some memory, as does Xen itself - > even if it''s only some small measures of memory...] > > -- > Mats >> >> Thanks, >> >> BJ Badyk >> >> _______________________________________________ >> 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
Also, im running with the "xen-3.0-x86_32-rhel4.1.bin" distro... On 10/2/06 11:09 AM, "Petersson, Mats" <Mats.Petersson@amd.com> wrote:> > >> -----Original Message----- >> From: xen-users-bounces@lists.xensource.com >> [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of >> Badyk, Benjamin >> Sent: 02 October 2006 16:56 >> To: xen-users@lists.xensource.com >> Subject: [Xen-users] Memory allocation >> >> I¹m sure this has been asked a bazillion times on this list, >> but I couldn¹t >> find a definitive answer: >> >> 4GB ram, 3 domU¹s >> >> I boot each domU up with 1GB ram, then mem-max and mem-set them to 2GB >> (which obviously exceeds physical memory limit). They all >> grow to 2048. It >> seems that you won¹t see the memory hit 2gb on a domU until >> it has eaten up >> more than what it initially booted with, which is fine. The >> question I have >> is what would happen if all three domU¹s tried using 2GB? > > If this actually works in the latest (unstable) release of Xen, I suggest you > report a bug. > > Something will go horribly wrong if you have 3 domU''s using 6GB of RAM on a > machine with 4GB or actual memory - it should not be possible to set it like > that. > > Xen doesn''t support "swapping" or in other ways overcommitting memory within > the domain memory allocation, so somewhere, you''ll have allocated the same > memory to more than one domain [assuming "xm list" shows all three domains to > have 2GB of RAM each] - which would obviously not work right... But I seem to > remember someone sending patches for "sanity checking mem-set", so it may be > that it''s fixed in the latest version. > > I can certainly guarantee that the one or more domains will crash and/or > corrupt themselves if you succeed in setting 2GB each for 3 domU''s on a 4GB > machine... [Not to mention that dom0 needs some memory, as does Xen itself - > even if it''s only some small measures of memory...] > > -- > Mats >> >> Thanks, >> >> BJ Badyk >> >> _______________________________________________ >> 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
On 10/2/06, Badyk, Benjamin <bbadyk@playboy.com> wrote:> Hey Mats, thanks for your help. I am actually able to set them beyond the > physical ram limit after they''ve been booted, eeek! > > > xenbox## xm list > Name ID Mem(MiB) VCPUs State Time(s) > Domain-0 0 230 4 r----- 815.1 > vm01 25 2048 2 -b---- 10733.4 > vm02 26 2048 2 -b---- 306.3 > vm03 27 2048 2 -b---- 305.0 > >I bet that if you go inside each of your VMs (via console or ssh) and do a ''cat /proc/meminfo'' the domains will not report a memtotal of 2GB. If they somehow do, then that''s probably not good. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users