Re: [RFC V2 03/12] mm: Change generic FALLBACK zonelist creation process

On 01/31/2017 12:55 PM, John Hubbard wrote:

On 01/30/2017 05:57 PM, Dave Hansen wrote:

quoted

On 01/30/2017 05:36 PM, Anshuman Khandual wrote:

quoted

quoted

Let's say we had a CDM node with 100x more RAM than the rest of the
system and it was just as fast as the rest of the RAM.  Would we still
want it isolated like this?  Or would we want a different policy?

But then the other argument being, dont we want to keep this 100X more
memory isolated for some special purpose to be utilized by specific
applications ?

I was thinking that in this case, we wouldn't even want to bother with
having "system RAM" in the fallback lists.  A device who got its memory
usage off by 1% could start to starve the rest of the system.  A sane
policy in this case might be to isolate the "system RAM" from the
device's.

I also don't like having these policies hard-coded, and your 100x
example above helps clarify what can go wrong about it. It would be
nicer if, instead, we could better express the "distance" between nodes
(bandwidth, latency, relative to sysmem, perhaps), and let the NUMA
system figure out the Right Thing To Do.

I realize that this is not quite possible with NUMA just yet, but I
wonder if that's a reasonable direction to go with this?

That is complete overhaul of the NUMA representation in the kernel. What
CDM attempts is to find a solution with existing NUMA framework and with
as little code change as possible.

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