Re: [PATCH 00/07][RFC] i386: NUMA emulation

Martin J. Bligh
2005-10-03T14:45:59Z

--David Lang <david.lang@digitalinsight.com> wrote (on Monday, October 03, 2005 00:34:40 -0700):

> On Mon, 3 Oct 2005, Magnus Damm wrote:
>
>> On 10/1/05, Dave Hansen <haveblue@us.ibm.com> wrote:
>>> On Fri, 2005-09-30 at 16:33 +0900, Magnus Damm wrote:
>>>> These patches implement NUMA memory node emulation for regular i386 PC:s.
>>>>
>>>> NUMA emulation could be used to provide coarse-grained memory resource control
>>>> using CPUSETS. Another use is as a test environment for NUMA memory code or
>>>> CPUSETS using an i386 emulator such as QEMU.
>>>
>>> This patch set basically allows the "NUMA depends on SMP" dependency to
>>> be removed. I'm not sure this is the right approach. There will likely
>>> never be a real-world NUMA system without SMP. So, this set would seem
>>> to include some increased (#ifdef) complexity for supporting SMP && !
>>> NUMA, which will likely never happen in the real world.
>>
>> Yes, this patch set removes "NUMA depends on SMP". It also adds some
>> simple NUMA emulation code too, but I am sure you are aware of that!
>> =)
>>
>> I agree that it is very unlikely to find a single-processor NUMA
>> system in the real world. So yes, "[PATCH 02/07] i386: numa on
>> non-smp" adds _some_ extra complexity. But because SMP is set when
>> supporting more than one cpu, and NUMA is set when supporting more
>> than one memory node, I see no reason why they should be dependent on
>> each other. Except that they depend on each other today and breaking
>> them loose will increase complexity a bit.
>
> hmm, observation from the peanut gallery, would it make sene to look at
> useing the NUMA code on single proc machines that use PAE to access
> more then 4G or ram on a 32 bit system?

2 problems:

1) there aren't any ;-)
2) The memory is not physically differently separated from the CPUs, so
it's not NUMA.

M.