Re: [Xen-devel] Memory allocation in NUMA system

[Andre Przywara <andre.przywara@xxxxxxx>]

Keir Fraser wrote:
> On 25/7/08 11:26, "Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx> wrote:
>
> > > Indeed the only reason we still have dma_bitsize is to break the
> > > select-NUMA-node-first memory allocation search strategy. So tweaking the
> > > dma_bitsize approach further to strike the correct NUMA-vs-DMA balance does
> > > seem the right thing to do. Feel free to work up a patch.
> > >
> > >  -- Keir
> > How about this one?
> Hmmm.. something like that. Let's wait until 3.4 development opens to get
> this checked in.
Mmh, why not check this in in 3.3? I have noticed this problem already a 
year ago and was having some other kind of fix for it (which actually 
prefered nodes over zones):
http://lists.xensource.com/archives/html/xen-devel/2007-12/msg00831.html
I think this is a somewhat serious issue on NUMA machines, since with 
the automatic pinning now active (new in 3.3!) many domains will end up 
with remote memory _all the time_. So I think of this as a bugfix. 
Actually I have dma_bitsize=30 hardwired in my Grub's menu.lst for some 
months now...
Regards,
Andre.

--
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 277-84917


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