fabi.a169@gmail.com
2008-Dec-19 21:31 UTC
[Xen-users] dom0 using only a single CPU (networking)
Hello, I''m using a server with 10Gbps network interfaces and 4 CPUs, running several domUs. The problem is that in this setup, with high network load, dom0 turns out to be the bottleneck, using only a single CPU which is saturated and 100%. So the network speed is bounded to much less than 10Gbps. How could I make dom0 use more CPUs in parallel ? I checked my VCPU setup; i have 4 VCPUs running assigned to dom0. For other kinds of programms running in dom0 user space, they are used. Could the problem be that the dom0 kernel uses a single thread for all the network forwarding and so can use only one CPU at a time ? If you have any idea, thank you for sharing your experience. Regards Fabi _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Mike O''Brien
2008-Dec-19 21:37 UTC
Re: [Xen-users] dom0 using only a single CPU (networking)
You don''t say what OS dom0 is running, but yes, it''s at least possible that network forwarding in that kernel uses a locking mechanism which squeezes everything through a single thread. Mike O''Brien _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Bastian Blank
2008-Dec-20 16:31 UTC
Re: [Xen-users] dom0 using only a single CPU (networking)
On Fri, Dec 19, 2008 at 10:31:54PM +0100, fabi.a169@gmail.com wrote:> I''m using a server with 10Gbps network interfaces and 4 CPUs, running > several domUs. The problem is that in this setup, with high network load, > dom0 turns out to be the bottleneck, using only a single CPU which is > saturated and 100%. So the network speed is bounded to much less than > 10Gbps. How could I make dom0 use more CPUs in parallel ?In short, you can''t. The Linux network stack uses polling to handle high load, however this can only run on one CPU at a time.> If you have any idea, thank you for sharing your experience.What sort of service do you run which can fill a 10GBit connection and is able to be virtualized at the same time? Bastian -- The idea of male and female are universal constants. -- Kirk, "Metamorphosis", stardate 3219.8 _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Ryan Burke
2008-Dec-22 17:16 UTC
Re: [Xen-users] dom0 using only a single CPU (networking)
> On Fri, Dec 19, 2008 at 10:31:54PM +0100, fabi.a169@gmail.com wrote: >> I''m using a server with 10Gbps network interfaces and 4 CPUs, running >> several domUs. The problem is that in this setup, with high network >> load, >> dom0 turns out to be the bottleneck, using only a single CPU which is >> saturated and 100%. So the network speed is bounded to much less than >> 10Gbps. How could I make dom0 use more CPUs in parallel ? > > In short, you can''t. The Linux network stack uses polling to handle high > load, however this can only run on one CPU at a time. > >> If you have any idea, thank you for sharing your experience. > > What sort of service do you run which can fill a 10GBit connection and > is able to be virtualized at the same time? > > BastianI would be interested in knowing if the network backend is capable of scaling with additional CPUs. Ryan _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users