Re: [PATCH RFC 0/5] workqueue: add WQ_AFFN_CACHE_SHARD affinity scope

[Tejun Heo]

Hello,

Applied 1/5. Some comments on the rest:

- The sharding currently splits on CPU boundary, which can split SMT
  siblings across different pods. The worse performance on Intel compared
  to SMT scope may be indicating exactly this - HT siblings ending up in
  different pods. It'd be better to shard on core boundary so that SMT
  siblings always stay together.

- How was the default shard size of 8 picked? There's a tradeoff between
  the number of kworkers created and locality. Can you also report the
  number of kworkers for each configuration? And is there data on
  different shard sizes? It'd be useful to see how the numbers change
  across e.g. 4, 8, 16, 32.

- Can you also test on AMD machines? Their CCD topology (16 or 32
  threads per LLC) would be a good data point.

Thanks.

--
tejun