[Libvir] [RFC][PATCH 1/2] Tested NUMA patches for available memory and topology
Ryan Harper
ryanh at us.ibm.com
Fri Sep 28 17:26:16 UTC 2007
* 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
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