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Diffstat (limited to 'Documentation/core-api/workqueue.rst')
| -rw-r--r-- | Documentation/core-api/workqueue.rst | 20 |
1 files changed, 16 insertions, 4 deletions
diff --git a/Documentation/core-api/workqueue.rst b/Documentation/core-api/workqueue.rst index e295835fc116..411e1b28b8de 100644 --- a/Documentation/core-api/workqueue.rst +++ b/Documentation/core-api/workqueue.rst @@ -183,6 +183,12 @@ resources, scheduled and executed. BH work items cannot sleep. All other features such as delayed queueing, flushing and canceling are supported. +``WQ_PERCPU`` + Work items queued to a per-cpu wq are bound to a specific CPU. + This flag is the right choice when cpu locality is important. + + This flag is the complement of ``WQ_UNBOUND``. + ``WQ_UNBOUND`` Work items queued to an unbound wq are served by the special worker-pools which host workers which are not bound to any @@ -372,9 +378,9 @@ Affinity Scopes An unbound workqueue groups CPUs according to its affinity scope to improve cache locality. For example, if a workqueue is using the default affinity -scope of "cache", it will group CPUs according to last level cache -boundaries. A work item queued on the workqueue will be assigned to a worker -on one of the CPUs which share the last level cache with the issuing CPU. +scope of "cache_shard", it will group CPUs into sub-LLC shards. A work item +queued on the workqueue will be assigned to a worker on one of the CPUs +within the same shard as the issuing CPU. Once started, the worker may or may not be allowed to move outside the scope depending on the ``affinity_strict`` setting of the scope. @@ -396,7 +402,13 @@ Workqueue currently supports the following affinity scopes. ``cache`` CPUs are grouped according to cache boundaries. Which specific cache boundary is used is determined by the arch code. L3 is used in a lot of - cases. This is the default affinity scope. + cases. + +``cache_shard`` + CPUs are grouped into sub-LLC shards of at most ``wq_cache_shard_size`` + cores (default 8, tunable via the ``workqueue.cache_shard_size`` boot + parameter). Shards are always split on core (SMT group) boundaries. + This is the default affinity scope. ``numa`` CPUs are grouped according to NUMA boundaries. |