The default nna (node_nr_active) is used when the pool isn't tied to a
specific NUMA node. This can happen in the following cases:
1. On NUMA, if per-node pwq init failure and the fallback pwq is used.
2. On NUMA, if a pool is configured to span multiple nodes.
3. On single node setups.
5797b1c189 ("workqueue: Implement system-wide nr_active enforcement for
unbound workqueues") set the default nna->max to min_active because only #1
was being considered. For #2 and #3, using min_active means that the max
concurrency in normal operation is pushed down to min_active which is
currently 8, which can obviously lead to performance issues.
exact value nna->max is set to doesn't really matter. #2 can only happen if
the workqueue is intentionally configured to ignore NUMA boundaries and
there's no good way to distribute max_active in this case. #3 is the default
behavior on single node machines.
Let's set it the default nna->max to max_active. This fixes the artificially
lowered concurrency problem on single node machines and shouldn't hurt
anything for other cases.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Fixes: 5797b1c189 ("workqueue: Implement system-wide nr_active enforcement for unbound workqueues")
Link: https://lore.kernel.org/dm-devel/20240410084531.2134621-1-shinichiro.kawasaki@wdc.com/
Signed-off-by: Tejun Heo <tj@kernel.org>
d40f92020c