Re: [PATCH sched_ext/for-7.2] sched_ext: Documentation: update scx_qmap description for BPF arena

Re: [PATCH sched_ext/for-7.2] sched_ext: Documentation: update scx_qmap description for BPF arena

[Tejun Heo]

Hello,

Thanks for catching this, but the proposed phrasing is a bit misleading.
BPF_MAP_TYPE_ARENA isn't a queue-map replacement for BPF_MAP_TYPE_QUEUE
- the arena is just memory; the queueing now happens through intrusive
doubly-linked lists in arena with per-queue bpf_res_spin_lock.

How about matching the file-level description in scx_qmap.bpf.c?

For Documentation/scheduler/sched-ext.rst:

  * ``scx_qmap[.bpf].c``: A multi-level FIFO scheduler supporting five
    levels of priority implemented with arena-backed doubly-linked lists.

For tools/sched_ext/README.md:

  Another simple, yet slightly more complex scheduler that provides an
  example of a basic weighted FIFO queuing policy. It also provides
  examples of some common useful BPF features, such as arena-backed
  doubly-linked lists threaded through per-task context and
  `bpf_res_spin_lock` for per-queue synchronization. It also illustrates
  how core-sched support could be implemented.

Thanks.

-- 
tejun