Re: Memory allocation in NUMA system

[Andre Przywara <andre.przywara@amd.com>]

Keir Fraser wrote:
> On 25/7/08 11:26, "Yang, Xiaowei" <xiaowei.yang@intel.com> 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