Gregory Price <gregory.price@xxxxxxxxxxxx> writes: > On Tue, Feb 27, 2024 at 08:38:19AM +0800, Huang, Ying wrote: >> Gregory Price <gregory.price@xxxxxxxxxxxx> writes: >> > Where are the 100 nodes coming from? >> >> If you have a real large machine with more than 100 nodes, and some of >> them are CXL memory nodes, then it's possible that most nodes will have >> interleave weight "1" because the sum of all interleave weights is >> "100". Then, even if you use only one socket, the interleave weight of >> DRAM and CXL MEM could be all "1", lead to useless default value. So, I >> suggest don't cap the sum of interleave weights. > > I have to press this issue: Is this an actual, practical, concern? I don't know who have large machine like that. But I guess that it's possible in the long run. > It seems to me in this type of scenario, there are larger, more complex > numa topology issues that make the use of the general, global weighted > mempolicy system entirely impractical. This is a bit outside the scope It's possible to solve the problem step by step. For example, add per-task interleave weight at some time. >> > So, long winded winded way of saying: >> > - Could we use a larger default number? Yes. >> > - Does that actually help us? Not really, we want smaller numbers. >> >> The larger number will be reduced after GCD. >> > > I suppose another strategy is to calculate the interleave weights > un-bounded from the raw bandwidth - but continuously force reductions > (through some yet-undefined algorithm) until at least one node reaches a > weight of `1`. This suffers from the opposite problem: what if the top > node has a value greater than 255? Do we just cap it at 255? That seems > the opposite form of problematic. > > (Large numbers are quite pointless, as it is essentially the antithesis > of interleave) Yes. So I suggest to use a relative small number as the default weight to start with for normal DRAM. We will have to floor/ceiling the weight value. -- Best Regards, Huang, Ying
