Hi There, Having read about this somewhere recently, am i correct in assuming that if you have a (say) dual processor server with dual core processors, that you can assign domU''s to individual cores? for example: 2 domUs on 1 core of one processor 1 domU on the other core of the same processor 1 domU to both cores of the other processor This allocation would of couse reflect the indented usage of domUs Regards, Simon _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Yes, that''d work. You can put domUs on any logical processor (hyperthread, core, real CPU package...). If the domUs are SMP you can spread them across several logical processors. Bear in mind dom0 has to go somewhere though ;-) On hyperthreaded systems there''s a benefit to allowing dom0 its own hyperthread so that it''s never context switched and is always available for servicing IO requests. On a multicore without HT, you might have it share a core with domUs, or dedicate a core - depending on your expected IO load. Cheers, Mark On Dec 7 2005, Simon wrote:>Hi There, Having read about this somewhere recently, am i correct in >assuming that if you have a (say) dual processor server with dual core >processors, that you can assign domU''s to individual cores? for >example: > >2 domUs on 1 core of one processor >1 domU on the other core of the same processor >1 domU to both cores of the other processor > >This allocation would of couse reflect the indented usage of domUs > >Regards, > >Simon > >_______________________________________________ >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
Keep in mind that Xen 2.0.7 seems to have problems with Dual Core A64s... Xen 3.0 seems to fix this problem, but we had some issues with 2.0.7 which made it impossible to use xen. M.A. Williamson wrote:> Yes, that''d work. You can put domUs on any logical processor > (hyperthread, core, real CPU package...). If the domUs are SMP you can > spread them across several logical processors. > > Bear in mind dom0 has to go somewhere though ;-) On hyperthreaded > systems there''s a benefit to allowing dom0 its own hyperthread so that > it''s never context switched and is always available for servicing IO > requests. > > On a multicore without HT, you might have it share a core with domUs, > or dedicate a core - depending on your expected IO load. > > Cheers, > Mark > > On Dec 7 2005, Simon wrote: > >> Hi There, Having read about this somewhere recently, am i correct in >> assuming that if you have a (say) dual processor server with dual core >> processors, that you can assign domU''s to individual cores? for >> example: >> >> 2 domUs on 1 core of one processor >> 1 domU on the other core of the same processor >> 1 domU to both cores of the other processor >> >> This allocation would of couse reflect the indented usage of domUs >> >> Regards, >> >> Simon >> >> _______________________________________________ >> 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 > > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On 07 Dec 2005 23:38:40 +0000, M.A. Williamson <maw48@cam.ac.uk> wrote:> Yes, that''d work. You can put domUs on any logical processor (hyperthread, > core, real CPU package...). If the domUs are SMP you can spread them across > several logical processors. > > Bear in mind dom0 has to go somewhere though ;-) On hyperthreaded systems > there''s a benefit to allowing dom0 its own hyperthread so that it''s never > context switched and is always available for servicing IO requests.dom0 services the IO (disk, ethernet etc) for all the domU''s?> > On a multicore without HT, you might have it share a core with domUs, or > dedicate a core - depending on your expected IO load._______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
>dom0 services the IO (disk, ethernet etc) for all the domU''s?Usually, yes. Unless you''re using driver domains (not in Xen 3.0 at the moment). Cheers, Mark>> >> On a multicore without HT, you might have it share a core with domUs, or >> dedicate a core - depending on your expected IO load. > >_______________________________________________ >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
Simon <greminn@gmail.com> wrote on 12/07/2005 05:31:59 PM:> Hi There, Having read about this somewhere recently, am i correct in > assuming that if you have a (say) dual processor server with dual core > processors, that you can assign domU''s to individual cores? for > example: > > 2 domUs on 1 core of one processor > 1 domU on the other core of the same processor > 1 domU to both cores of the other processor > > This allocation would of couse reflect the indented usage of domUsIn Xen 3.0 you can use the "cpus=" option in the domain configuration file to set which cpus the domain''s vcpus should map to. As far as I know, you can''t map the vcpus to cores or processors directly; you map vcpus to cpus. In my experience, you have to know ahead of time which processor and core a CPU is on in order to know what the vcpu should map to. And the assignment of CPU numbers is not necessarily in a linear fashion, e.g. with hyperthreading, CPU 0 ->core 0 -> processor 0, CPU 1 ->core 0 -> processor 0, CPU 2 ->core 1 -> processor 0, ... , CPU 4 ->core 0 -> processor 1, etc. The only way I have found so far to discover Xen''s mapping of CPUS to processors and cores is to examine the output of "xm dmesg". I wrote a little script to parse the output of "xm dmesg", extract the CPU information, and print it out in a simpler format. Here is some sample output from my 4 processor, dual core, hyperthreaded machine. Processor 0, Core 0, CPU 0 Processor 0, Core 0, CPU 10 Processor 0, Core 1, CPU 6 Processor 0, Core 1, CPU 14 Processor 1, Core 2, CPU 7 Processor 1, Core 2, CPU 15 Processor 1, Core 3, CPU 3 Processor 1, Core 3, CPU 11 Processor 2, Core 4, CPU 1 Processor 2, Core 4, CPU 8 Processor 2, Core 5, CPU 4 Processor 2, Core 5, CPU 12 Processor 3, Core 6, CPU 5 Processor 3, Core 6, CPU 13 Processor 3, Core 7, CPU 2 Processor 3, Core 7, CPU 9 As you can see the assignments are not linear according to IDs. If dom0 is running on cpu 0 and I want to put my domU on another processor, I can set "cpus=1-5,7-9,11-13,15". Not very straight forward, but it works. Anyone with better knowledge or experience, feel free to comment and correct. Steve D. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On 12/8/05, Steve Dobbelstein <steved@us.ibm.com> wrote:> I wrote a little script to parse the output of "xm dmesg", extract the CPU > information, and print it out in a simpler format. Here is some sample > output from my 4 processor, dual core, hyperthreaded machine.Hmm - quite interesting! So a good optimum Xen processor would be a MP, dual-core, HT processor - this gives you quite abit of flexibility with domU''s im guessing. What specific processor''s are you using for your server, also, is it a brand-name? I would be interested in hearing about the HW involved and what you are using them for (generally eg how many domUs and what they do). As i am sorting initial thoughts on our HW choices at the moment. Simon _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On 12/8/05, Steve Dobbelstein <steved@us.ibm.com> wrote:> I wrote a little script to parse the output of "xm dmesg", extract the CPU > information, and print it out in a simpler format. Here is some sample > output from my 4 processor, dual core, hyperthreaded machine.Im guessing it might be an IBM server? Can you share your script? Simon _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Simon <greminn@gmail.com> wrote on 12/07/2005 08:13:32 PM:> On 12/8/05, Steve Dobbelstein <steved@us.ibm.com> wrote: > > > I wrote a little script to parse the output of "xm dmesg", extract theCPU> > information, and print it out in a simpler format. Here is some sample > > output from my 4 processor, dual core, hyperthreaded machine. > > Can you share your script?(See attached file: xen-cpu-topology) Disclaimer: The script was a quick little write-up to put the CPU information from "xm dmesg" into a form that I could quickly understand. It doesn''t have a whole lot of error handling. It is based on my observations of the "xm dmesg" output I gathered from two machines. It is possible that the script may not parse correctly "xm dmesg" output from your machine if it is significantly different from what I observed on my two machines. It is possible the script may not parse correctly any future output of "xm dmesg" if Xen changes the format of what it reports. That said, I hope the script is useful and will welcome any comments, suggestions, and corrections. Steve D. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On 12/9/05, Steve Dobbelstein <steved@us.ibm.com> wrote:> Simon <greminn@gmail.com> wrote on 12/07/2005 08:13:32 PM: > > > On 12/8/05, Steve Dobbelstein <steved@us.ibm.com> wrote: > > > > > I wrote a little script to parse the output of "xm dmesg", extract the > CPU > > > information, and print it out in a simpler format. Here is some sample > > > output from my 4 processor, dual core, hyperthreaded machine. > > > > Can you share your script? > > (See attached file: xen-cpu-topology) > > Disclaimer: The script was a quick little write-up to put the CPU > information from "xm dmesg" into a form that I could quickly understand. > It doesn''t have a whole lot of error handling. It is based on my > observations of the "xm dmesg" output I gathered from two machines. It is > possible that the script may not parse correctly "xm dmesg" output from > your machine if it is significantly different from what I observed on my > two machines. It is possible the script may not parse correctly any future > output of "xm dmesg" if Xen changes the format of what it reports. > > That said, I hope the script is useful and will welcome any comments, > suggestions, and corrections. > > Steve D.THanks Steve, What specific processor''s are you using for your server, also, is it a brand-name? I would be interested in hearing about the HW involved and what you are using them for (generally eg how many domUs and what they do). As i am sorting initial thoughts on our HW choices at the moment. We are currently looking at IBM sSeries dual-processor servers with dual core processors. These have been released in the US and are schduled for release here (in New Zealand) Jan 2006. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users