[PATCH v15 0/6] Add NUMA-awareness to qspinlock

[Barry Song]

> We have done some performance evaluation with the locktorture module
> as well as with several benchmarks from the will-it-scale repo.
> The following locktorture results are from an Oracle X5-4 server
> (four Intel Xeon E7-8895 v3 @ 2.60GHz sockets with 18 hyperthreaded
> cores each). Each number represents an average (over 25 runs) of the
> total number of ops (x10^7) reported at the end of each run. The 
> standard deviation is also reported in (), and in general is about 3%
> from the average. The 'stock' kernel is v5.12.0,

I assume x5-4 server has the crossbar topology and its numa diameter is
1hop, and all tests were done on this kind of symmetrical topology. Am
I right? 

    ┌─┐                 ┌─┐
    │ ├─────────────────┤ │
    └─┤1               1└┬┘
      │  1           1   │
      │    1       1     │
      │      1   1       │
      │        1         │
      │      1   1       │
      │     1      1     │
      │   1         1    │
     ┌┼┐1             1  ├─┐
     │┼┼─────────────────┤ │
     └─┘                 └─┘


what if the hardware is using the ring topology and other topologies with
2-hops or even 3-hops such as:

     ┌─┐                 ┌─┐
     │ ├─────────────────┤ │
     └─┤                 └┬┘
       │                  │
       │                  │
       │                  │
       │                  │
       │                  │
       │                  │
       │                  │
      ┌┤                  ├─┐
      │┼┬─────────────────┤ │
      └─┘                 └─┘


or:


    ┌───┐       ┌───┐      ┌────┐      ┌─────┐
    │   │       │   │      │    │      │     │
    │   │       │   │      │    │      │     │
    ├───┼───────┼───┼──────┼────┼──────┼─────┤
    │   │       │   │      │    │      │     │
    └───┘       └───┘      └────┘      └─────┘

do we need to consider the distances of numa nodes in the secondary
queue? does it still make sense to treat everyone else equal in
secondary queue?

Thanks
barry