[Libvir] [RFC][PATCH 1/2] Tested NUMA patches for available memory and topology

[Ryan Harper]

* Richard W.M. Jones <rjones at redhat.com> [2007-09-28 11:20]:
> beth kon wrote:
> >Richard W.M. Jones wrote:
> >
> >>My results are a bit inconclusive.  I have a machine here which 
> >>supposedly supports NUMA (2 socket, 2 core AMD with hypertransport and 
> >>two separate banks of RAM).
> >>
> >>BIOS is _not_ configured to interleave memory.  Other BIOS settings 
> >>lead me to suppose that NUMA is enabled (or at least not disabled).
> >>
> >>Booting with Daniel's Xen & kernel does not give any messages about 
> >>NUMA enabled or disabled.  (See attached messages).
> >>
> >># numactl --show
> >>physcpubind: 0 1 2 3
> >>No NUMA support available on this system.
> >>
> >Are you setting "numa=on dom0_mem=512m" on the kernel line in grub? I'm 
> >not sure if the dom0_mem=512m should be required but we were having 
> >problems when trying to boot numa without it.
> 
> Aha, the results are quite a bit better now :-)
> 
> virsh shows the correct topology:
> 
>   <topology>
>     <cells num='2'>
>       <cell id='0'>
>         <cpus num='2'>
>            <cpu id='0'/>
>            <cpu id='1'/>
>         </cpus>
>       </cell>
>       <cell id='1'>
>         <cpus num='2'>
>            <cpu id='2'/>
>            <cpu id='3'/>
>         </cpus>
>       </cell>
>     </cells>
>   </topology>
> 
> numactl --show still doesn't work (missing support in dom0 kernel or is 
> this just completely incompatible with Xen?)

Currently Xen doesn't export any per-domain topology (say a virtual SRAT
table), nor the entire system topology; the goal of the current Xen NUMA
code is to ensure that domains have local resources within a numa-node.  

> 
> 'virsh freecell 0' and 'virsh freecell 1' show numbers which are 
> plausible (I have no idea if they're actually correct though).
> 
> Can I pin a domain or vCPU to memory to see if that works?
> 
> Rich.
> 
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-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
(512) 838-9253   T/L: 678-9253
ryanh at us.ibm.com