Re: [Xen-devel] Re: NUMA and SMP

[Daniel Stodden <stodden@xxxxxxxxxx>]

On Thu, 2007-03-22 at 20:13 +0800, tgh wrote:
> Thank you for your reply
> 
> 
> 
> >   
> >> in the smp with adm64 with the hardware of numa, its linux is a smp os 
> >> ,then there is only one node (struct pglist_data) in the os when running 
> >> or  there are as many nodes as cpus in the system,  does linux smp 
> >> support two or more nodes when running? or in this case linux support 
> >> numa feature?
> >>     
> >
> > the number of nodes corresponds to the number of memory areas which
> > allocators need distinguish. in the case of integrated memory
> > controllers like amd64, expect to find as many nodes as there are
> > processors. 
> >
> > yes, linux has numa support. see linux/Documentation/vm/
> >   
> 
> linux has numa support,and in the case of integrated memory controllers 
> like amd64, CONFIG_NUMA should be choice and linux support numa,is it 
> right? if CONFIG_NUMA is not choice ,then linux could not work well in 
> the case of integrated memory controllers even for amd64,is it right? 


> and for the paravirt xen-guest-linux do not support  numa-aware  now ,or 
> does it  support  numa-aware  if CONFIG_NUMA choiced?

no. there is num-support in xen, as far as inspection of the memory
topology and inclusion in the memory management is concerned. so
basically, you can add the desired node number to get_free_pages().

there is numa support in linux to a somewhat larger degree.

but...

config NUMA
       bool "Non Uniform Memory Access (NUMA) Support"
       depends on SMP && !X86_64_XEN

...there is no numa-support for paravirtual kernels at this point in
time.

see, you can't just switch it on and expect anything to improve. the vm
may typically see a subset of the cpus/nodes physically available, with
no reflection on their mapping to physical nodes. page migration between
logical cpus is pointless if logical cpus migrate across physical ones,
right?

regards,
daniel

-- 
Daniel Stodden
LRR     -      Lehrstuhl fÃr Rechnertechnik und Rechnerorganisation
Institut fÃr Informatik der TU MÃnchen             D-85748 Garching
http://www.lrr.in.tum.de/~stodden         mailto:stodden@xxxxxxxxxx
PGP Fingerprint: F5A4 1575 4C56 E26A 0B33  3D80 457E 82AE B0D8 735B


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