lei yang
2010-May-21 03:09 UTC
[Xen-users] What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and "dom0_max_vcpus=4" ?
Hi experts, Q1:What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and "dom0_max_vcpus=4" ? which will get better performance Q2: dom0_max_vcpus=4 means "core0-3 will be just used by dom0" or means "4 cores(not dedicate cores) will be used by dom0, eg: core2-5 or core3-6? Q3.what does mean "nosmp" , xen, dom0,domU, will just use one core????if so, can we specify the use different core. eg: dom0=core2 domU=core3? xen will use just one core? Thanks Lei -- "We learn from failure, not from success!" _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Keir Fraser
2010-May-21 06:57 UTC
Re: [Xen-devel] What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and "dom0_max_vcpus=4" ?
On 21/05/2010 04:09, "lei yang" <yanglei.fage@gmail.com> wrote:> Hi experts, > > > Q1:What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and > "dom0_max_vcpus=4" ? which will get better performanceThe former restricts Xen to only run Dom0 VCPUs 0-3 on physical CPUs 0-3. It''s not really a performance thing, but instead is to mean that some things like cpufreq management can work directly from dom0. We don''t really use the dom0_vcpus_pin option much.> Q2: dom0_max_vcpus=4 means "core0-3 will be just used by dom0" or means "4 > cores(not dedicate cores) will be used by dom0, eg: core2-5 or core3-6?Dom0''s VCPUs can be scheduled on any physical CPU at any time, unles dom0_vcpus_pin is specified.> Q3.what does mean "nosmp" , xen, dom0,domU, will just use one core????if so, > can we specify the use different core. eg: dom0=core2 domU=core3? xen will use > just one core?It brings Xen up on the boot CPU only. Nothing in the system will use the other CPUs. You don''t want to use this option really. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Robert Dunkley
2010-May-21 12:02 UTC
RE: [Xen-users] What''s the different for "dom0_max_vcpus=4dom0_vcpus_pin" and "dom0_max_vcpus=4" ?
Hi Lei, Q1: The pin is needed to lock Dom0 to cores 0 & 1. Q2: It means 4 vcpus are allocated to Dom0, they can float between physical cores. VCPUs don''t really line up with cores, you can assign 8 vcpus on a DomU on a 4 core Dom0 box for example. 8 cpus will appear in the VM but Xen will try to allocate the request within its 4 physucal cores. Generally assigning more VPUs than you have physical cores is pointless. Q3: No SMP for a DOMU will mean the kernel is not SMP aware, this can save a small amount of overhead and improve scheduling in certain cases on a single core DOMU. I''m not sure what the affect would be on Dom0, my guess is it won''t be good. Rob From: xen-users-bounces@lists.xensource.com [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of lei yang Sent: 21 May 2010 04:09 To: Xen Mailing List; xen-devel@lists.xensource.com Subject: [Xen-users] What''s the different for "dom0_max_vcpus=4dom0_vcpus_pin" and "dom0_max_vcpus=4" ? Hi experts, Q1:What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and "dom0_max_vcpus=4" ? which will get better performance Q2: dom0_max_vcpus=4 means "core0-3 will be just used by dom0" or means "4 cores(not dedicate cores) will be used by dom0, eg: core2-5 or core3-6? Q3.what does mean "nosmp" , xen, dom0,domU, will just use one core????if so, can we specify the use different core. eg: dom0=core2 domU=core3? xen will use just one core? Thanks Lei -- "We learn from failure, not from success!" The SAQ Group Registered Office: 18 Chapel Street, Petersfield, Hampshire GU32 3DZ SAQ is the trading name of SEMTEC Limited. Registered in England & Wales Company Number: 06481952 http://www.saqnet.co.uk AS29219 SAQ Group Delivers high quality, honestly priced communication and I.T. services to UK Business. Broadband : Domains : Email : Hosting : CoLo : Servers : Racks : Transit : Backups : Managed Networks : Remote Support. ISPA Member _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
lei yang
2010-May-21 15:38 UTC
Re: [Xen-users] What''s the different for "dom0_max_vcpus=4dom0_vcpus_pin" and "dom0_max_vcpus=4" ?
On Fri, May 21, 2010 at 8:02 PM, Robert Dunkley <Robert@saq.co.uk> wrote:> Hi Lei, > > > > > > Q1: The pin is needed to lock Dom0 to cores 0 & 1. > > >dom0_max_vcpus=4 dom0_vcpus_pin just lock Dom0 to cores0 and 1?? but it''s "4"> Q2: It means 4 vcpus are allocated to Dom0, they can float between > physical cores. >dom0_max_vcpus=4 , can be the 4 cores=2 3 4 5, does it will change to 1 2 3 4? or just bind to 2 3 4 5 dom0_max_vcpus=4 dom0_vcpus_pin will just to core0-3?> VCPUs don’t really line up with cores, you can assign 8 vcpus on a DomU > on a 4 core Dom0 box for example. 8 cpus will appear in the VM but Xen will > try to allocate the request within its 4 physucal cores. Generally assigning > more VPUs than you have physical cores is pointless. > > > > Q3: No SMP for a DOMU will mean the kernel is not SMP aware, this can save > a small amount of overhead and improve scheduling in certain cases on a > single core DOMU. I’m not sure what the affect would be on Dom0, my guess is > it won’t be good. > > > > > > > > Rob > > > > *From:* xen-users-bounces@lists.xensource.com [mailto: > xen-users-bounces@lists.xensource.com] *On Behalf Of *lei yang > *Sent:* 21 May 2010 04:09 > *To:* Xen Mailing List; xen-devel@lists.xensource.com > *Subject:* [Xen-users] What''s the different for > "dom0_max_vcpus=4dom0_vcpus_pin" and "dom0_max_vcpus=4" ? > > > > Hi experts, > > > Q1:What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and > "dom0_max_vcpus=4" ? > which will get better performance > > Q2: dom0_max_vcpus=4 means "core0-3 will be just used by dom0" or means "4 > cores(not dedicate cores) will be used by dom0, eg: core2-5 or core3-6? > > Q3.what does mean "nosmp" , xen, dom0,domU, will just use one core????if > so, can we specify the use different core. eg: dom0=core2 domU=core3? xen > will use just one core? > > Thanks > Lei > > > > > > > > > -- > "We learn from failure, not from success!" > > ** > > *The SAQ Group* > > *Registered Office: 18 Chapel Street, Petersfield, Hampshire GU32 3DZ* > SAQ is the trading name of SEMTEC Limited. Registered in England & Wales > Company Number: 06481952 > > > > http://www.saqnet.co.uk AS29219 > > SAQ Group Delivers high quality, honestly priced communication and I.T. > services to UK Business. > > Broadband : Domains : Email : Hosting : CoLo : Servers : Racks : Transit : > Backups : Managed Networks : Remote Support. > > > > [image: SAQ Group] > > > > *ISPA Member* >-- "We learn from failure, not from success!" _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
lei yang
2010-May-21 15:39 UTC
Re: [Xen-devel] What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and "dom0_max_vcpus=4" ?
On Fri, May 21, 2010 at 2:57 PM, Keir Fraser <keir.fraser@eu.citrix.com>wrote:> On 21/05/2010 04:09, "lei yang" <yanglei.fage@gmail.com> wrote: > > > Hi experts, > > > > > > Q1:What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and > > "dom0_max_vcpus=4" ? which will get better performance > > The former restricts Xen to only run Dom0 VCPUs 0-3 on physical CPUs 0-3. >dom0_max_vcpus=4 dom0_vcpus_pin will just to core0-3? can it be 3 4 5 6? if remove "dom0_vcpus_pin" just use " dom0_max_vcpus=4 " can it be 3 4 5 6 ?> It''s not really a performance thing, but instead is to mean that some > things > like cpufreq management can work directly from dom0. We don''t really use > the > dom0_vcpus_pin option much. > > > Q2: dom0_max_vcpus=4 means "core0-3 will be just used by dom0" or means > "4 > > cores(not dedicate cores) will be used by dom0, eg: core2-5 or core3-6? > > Dom0''s VCPUs can be scheduled on any physical CPU at any time, unles > dom0_vcpus_pin is specified. > > > Q3.what does mean "nosmp" , xen, dom0,domU, will just use one core????if > so, > > can we specify the use different core. eg: dom0=core2 domU=core3? xen > will use > > just one core? > > It brings Xen up on the boot CPU only. Nothing in the system will use the > other CPUs. You don''t want to use this option really. > > -- Keir > > >-- "We learn from failure, not from success!" _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Pasi Kärkkäinen
2010-May-21 15:46 UTC
Re: [Xen-devel] What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and "dom0_max_vcpus=4" ?
On Fri, May 21, 2010 at 11:39:50PM +0800, lei yang wrote:> On Fri, May 21, 2010 at 2:57 PM, Keir Fraser > <[1]keir.fraser@eu.citrix.com> wrote: > > On 21/05/2010 04:09, "lei yang" <[2]yanglei.fage@gmail.com> wrote: > > > Hi experts, > > > > > > Q1:What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and > > "dom0_max_vcpus=4" ? which will get better performance > > The former restricts Xen to only run Dom0 VCPUs 0-3 on physical CPUs > 0-3. > > > dom0_max_vcpus=4 dom0_vcpus_pin will just to core0-3? >Yes.> can it be 3 4 5 6? >Yes, modify the pinning when the system has booted up using "xm vcpu-pin".> if remove "dom0_vcpus_pin" just use " dom0_max_vcpus=4 " can it be 3 4 5 > 6 ? >Yes, set up the pinning yourself. -- Pasi> > It''s not really a performance thing, but instead is to mean that some > things > like cpufreq management can work directly from dom0. We don''t really use > the > dom0_vcpus_pin option much. > > Q2: dom0_max_vcpus=4 means "core0-3 will be just used by dom0" or > means "4 > > cores(not dedicate cores) will be used by dom0, eg: core2-5 or > core3-6? > > Dom0''s VCPUs can be scheduled on any physical CPU at any time, unles > dom0_vcpus_pin is specified. > > Q3.what does mean "nosmp" , xen, dom0,domU, will just use one > core????if so, > > can we specify the use different core. eg: dom0=core2 domU=core3? xen > will use > > just one core? > > It brings Xen up on the boot CPU only. Nothing in the system will use > the > other CPUs. You don''t want to use this option really. > -- Keir > > -- > "We learn from failure, not from success!" > > References > > Visible links > 1. mailto:keir.fraser@eu.citrix.com > 2. mailto:yanglei.fage@gmail.com> _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
lei yang
2010-May-21 15:51 UTC
Re: [Xen-devel] What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and "dom0_max_vcpus=4" ?
On Fri, May 21, 2010 at 11:46 PM, Pasi Kärkkäinen <pasik@iki.fi> wrote:> On Fri, May 21, 2010 at 11:39:50PM +0800, lei yang wrote: > > On Fri, May 21, 2010 at 2:57 PM, Keir Fraser > > <[1]keir.fraser@eu.citrix.com> wrote: > > > > On 21/05/2010 04:09, "lei yang" <[2]yanglei.fage@gmail.com> wrote: > > > > > Hi experts, > > > > > > > > > Q1:What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and > > > "dom0_max_vcpus=4" ? which will get better performance > > > > The former restricts Xen to only run Dom0 VCPUs 0-3 on physical CPUs > > 0-3. > > > > > > dom0_max_vcpus=4 dom0_vcpus_pin will just to core0-3? > > > > Yes. > > > can it be 3 4 5 6? > > > > Yes, modify the pinning when the system has booted up using "xm vcpu-pin". > >if I don''t use "xm vcpu-pin" does it will use core 0 1 2 3 by default not can use 3 4 5 6? if so, does core 0-4 just can used by dom0? domU can''t use it? Thanks Lei> > if remove "dom0_vcpus_pin" just use " dom0_max_vcpus=4 " can it be 3 > 4 5 > > 6 ? > > > > Yes, set up the pinning yourself. > >again. if just use "dom0_max_vcpus=4" not use "dom0_vcpus_pin" and I don''t use "xm vcpu-pin", can ''t be 3 4 5 6, Thanks Lei> -- Pasi > > > > > It''s not really a performance thing, but instead is to mean that > some > > things > > like cpufreq management can work directly from dom0. We don''t really > use > > the > > dom0_vcpus_pin option much. > > > Q2: dom0_max_vcpus=4 means "core0-3 will be just used by dom0" or > > means "4 > > > cores(not dedicate cores) will be used by dom0, eg: core2-5 or > > core3-6? > > > > Dom0''s VCPUs can be scheduled on any physical CPU at any time, unles > > dom0_vcpus_pin is specified. > > > Q3.what does mean "nosmp" , xen, dom0,domU, will just use one > > core????if so, > > > can we specify the use different core. eg: dom0=core2 domU=core3? > xen > > will use > > > just one core? > > > > It brings Xen up on the boot CPU only. Nothing in the system will > use > > the > > other CPUs. You don''t want to use this option really. > > -- Keir > > > > -- > > "We learn from failure, not from success!" > > > > References > > > > Visible links > > 1. mailto:keir.fraser@eu.citrix.com > > 2. mailto:yanglei.fage@gmail.com > > > _______________________________________________ > > Xen-devel mailing list > > Xen-devel@lists.xensource.com > > http://lists.xensource.com/xen-devel > >-- "We learn from failure, not from success!" _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Pasi Kärkkäinen
2010-May-21 15:55 UTC
Re: [Xen-devel] What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and "dom0_max_vcpus=4" ?
On Fri, May 21, 2010 at 11:51:34PM +0800, lei yang wrote:> On Fri, May 21, 2010 at 11:46 PM, Pasi Kärkkäinen <[1]pasik@iki.fi> wrote: > > On Fri, May 21, 2010 at 11:39:50PM +0800, lei yang wrote: > > On Fri, May 21, 2010 at 2:57 PM, Keir Fraser > > <[1][2]keir.fraser@eu.citrix.com> wrote: > > > > On 21/05/2010 04:09, "lei yang" <[2][3]yanglei.fage@gmail.com> > wrote: > > > > > Hi experts, > > > > > > > > > Q1:What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" > and > > > "dom0_max_vcpus=4" ? which will get better performance > > > > The former restricts Xen to only run Dom0 VCPUs 0-3 on physical > CPUs > > 0-3. > > > > > > dom0_max_vcpus=4 dom0_vcpus_pin will just to core0-3? > > > > Yes. > > can it be 3 4 5 6? > > > > Yes, modify the pinning when the system has booted up using "xm > vcpu-pin". > > > > if I don''t use "xm vcpu-pin" does it will use core 0 1 2 3 by default not > can use 3 4 5 6? >Yes, it''ll use 0 1 2 3 as a default. It cannot be changed, unless you do custom pinning after the system has started.> if so, does core 0-4 just can used by dom0? domU can''t use it? >domU can (and will) use them, so you need to also pin the domUs so that they won''t try to use the dom0 cores, if you absolutely want to dedicate 4 cores only for dom0. Just play with "xm vcpu-pin" and "xm vcpu-list" and you''ll figure it out. -- Pasi> Thanks > Lei > > > > if remove "dom0_vcpus_pin" just use " dom0_max_vcpus=4 " can it be > 3 4 5 > > 6 ? > > > > Yes, set up the pinning yourself. > > > again. if just use "dom0_max_vcpus=4" not use "dom0_vcpus_pin" and I > don''t use "xm vcpu-pin", can ''t be 3 4 5 6, > > Thanks > Lei > > > -- Pasi > > > > It''s not really a performance thing, but instead is to mean that > some > > things > > like cpufreq management can work directly from dom0. We don''t > really use > > the > > dom0_vcpus_pin option much. > > > Q2: dom0_max_vcpus=4 means "core0-3 will be just used by dom0" > or > > means "4 > > > cores(not dedicate cores) will be used by dom0, eg: core2-5 or > > core3-6? > > > > Dom0''s VCPUs can be scheduled on any physical CPU at any time, > unles > > dom0_vcpus_pin is specified. > > > Q3.what does mean "nosmp" , xen, dom0,domU, will just use one > > core????if so, > > > can we specify the use different core. eg: dom0=core2 > domU=core3? xen > > will use > > > just one core? > > > > It brings Xen up on the boot CPU only. Nothing in the system will > use > > the > > other CPUs. You don''t want to use this option really. > > -- Keir > > > > -- > > "We learn from failure, not from success!" > > > > References > > > > Visible links > > 1. mailto:[4]keir.fraser@eu.citrix.com > > 2. mailto:[5]yanglei.fage@gmail.com > > _______________________________________________ > > Xen-devel mailing list > > [6]Xen-devel@lists.xensource.com > > [7]http://lists.xensource.com/xen-devel > > -- > "We learn from failure, not from success!" > > References > > Visible links > 1. mailto:pasik@iki.fi > 2. mailto:keir.fraser@eu.citrix.com > 3. mailto:yanglei.fage@gmail.com > 4. mailto:keir.fraser@eu.citrix.com > 5. mailto:yanglei.fage@gmail.com > 6. mailto:Xen-devel@lists.xensource.com > 7. http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Keir Fraser
2010-May-21 15:59 UTC
[Xen-users] Re: [Xen-devel] What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and "dom0_max_vcpus=4" ?
On 21/05/2010 16:39, "lei yang" <yanglei.fage@gmail.com> wrote:>> The former restricts Xen to only run Dom0 VCPUs 0-3 on physical CPUs 0-3. > > dom0_max_vcpus=4 dom0_vcpus_pin will just to core0-3? can it be 3 4 5 6? > if remove "dom0_vcpus_pin" just use " dom0_max_vcpus=4 " can it be 3 4 5 6 ?No, but you can set whatever affinity you like after dom0 has booted. For example, to pin Dom0 VCPUs 0-3 to CPUs 3-6 respectively: xl vcpu-pin 0 0 3 xl vcpu-pin 0 1 4 xl vcpu-pin 0 2 5 xl vcpu-pin 0 3 6 (or use xm vcpu-pin if you are not using the new xl command). -- Keir _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Keir Fraser
2010-May-21 16:09 UTC
[Xen-users] Re: [Xen-devel] What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and "dom0_max_vcpus=4" ?
On 21/05/2010 16:55, "Pasi Kärkkäinen" <pasik@iki.fi> wrote:>> if I don''t use "xm vcpu-pin" does it will use core 0 1 2 3 by default not >> can use 3 4 5 6? >> > > Yes, it''ll use 0 1 2 3 as a default. It cannot be changed, unless you do > custom pinning after the system has started.It will only stick to 0 1 2 3 if you specify dom0_vcpus_pin on the Xen command line. And if you do that, then the pinning canno tbe changed by xm/xl vcpu-pin. If you do not specify dom0_vcpus_pin then dom0 VCPUs will execute on arbitrary physical CPUs until you restrict each VCPU''s affinity using xm/xl vcpu-pin. By default, any VCPU (whether dom0''s or a domU''s) can be executed at any time on any physical CPU. If there are CPUs you specifically want to restrict a given VCPU or domain to, then you have to get busy with xm/xl vcpu-pin. Anyway, I think that is this particular horse flogged to death. No more on xen-devel please. K. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
lei yang
2010-May-21 16:14 UTC
[Xen-users] Re: [Xen-devel] What''s the different for "dom0_max_vcpus=4 dom0_vcpus_pin" and "dom0_max_vcpus=4" ?
I want to improve the lmbench results. can you give me some points to improve it? from kernel userspace glibc gcc view or whatever else. Thanks Lei On Sat, May 22, 2010 at 12:09 AM, Keir Fraser <keir.fraser@eu.citrix.com>wrote:> On 21/05/2010 16:55, "Pasi Kärkkäinen" <pasik@iki.fi> wrote: > > >> if I don''t use "xm vcpu-pin" does it will use core 0 1 2 3 by default > not > >> can use 3 4 5 6? > >> > > > > Yes, it''ll use 0 1 2 3 as a default. It cannot be changed, unless you do > > custom pinning after the system has started. > > It will only stick to 0 1 2 3 if you specify dom0_vcpus_pin on the Xen > command line. And if you do that, then the pinning canno tbe changed by > xm/xl vcpu-pin. > > If you do not specify dom0_vcpus_pin then dom0 VCPUs will execute on > arbitrary physical CPUs until you restrict each VCPU''s affinity using xm/xl > vcpu-pin. > > By default, any VCPU (whether dom0''s or a domU''s) can be executed at any > time on any physical CPU. If there are CPUs you specifically want to > restrict a given VCPU or domain to, then you have to get busy with xm/xl > vcpu-pin. > > Anyway, I think that is this particular horse flogged to death. No more on > xen-devel please. > > K. > > >-- "We learn from failure, not from success!" _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users