summaryrefslogtreecommitdiffstats
path: root/drivers/net/ethernet
diff options
context:
space:
mode:
authorTejun Heo <tj@kernel.org>2013-04-01 11:23:36 -0700
committerTejun Heo <tj@kernel.org>2013-04-01 11:23:36 -0700
commit4c16bd327c74d6678858706211a0c6e4e53eb3e6 (patch)
treeaa14cf2c9ed0a95e8e0deea60e4464dcd55d1289 /drivers/net/ethernet
parentdce90d47c4288c7d3c1988bebb059ea7451d5fd5 (diff)
downloadblackbird-op-linux-4c16bd327c74d6678858706211a0c6e4e53eb3e6.tar.gz
blackbird-op-linux-4c16bd327c74d6678858706211a0c6e4e53eb3e6.zip
workqueue: implement NUMA affinity for unbound workqueues
Currently, an unbound workqueue has single current, or first, pwq (pool_workqueue) to which all new work items are queued. This often isn't optimal on NUMA machines as workers may jump around across node boundaries and work items get assigned to workers without any regard to NUMA affinity. This patch implements NUMA affinity for unbound workqueues. Instead of mapping all entries of numa_pwq_tbl[] to the same pwq, apply_workqueue_attrs() now creates a separate pwq covering the intersecting CPUs for each NUMA node which has online CPUs in @attrs->cpumask. Nodes which don't have intersecting possible CPUs are mapped to pwqs covering whole @attrs->cpumask. As CPUs come up and go down, the pool association is changed accordingly. Changing pool association may involve allocating new pools which may fail. To avoid failing CPU_DOWN, each workqueue always keeps a default pwq which covers whole attrs->cpumask which is used as fallback if pool creation fails during a CPU hotplug operation. This ensures that all work items issued on a NUMA node is executed on the same node as long as the workqueue allows execution on the CPUs of the node. As this maps a workqueue to multiple pwqs and max_active is per-pwq, this change the behavior of max_active. The limit is now per NUMA node instead of global. While this is an actual change, max_active is already per-cpu for per-cpu workqueues and primarily used as safety mechanism rather than for active concurrency control. Concurrency is usually limited from workqueue users by the number of concurrently active work items and this change shouldn't matter much. v2: Fixed pwq freeing in apply_workqueue_attrs() error path. Spotted by Lai. v3: The previous version incorrectly made a workqueue spanning multiple nodes spread work items over all online CPUs when some of its nodes don't have any desired cpus. Reimplemented so that NUMA affinity is properly updated as CPUs go up and down. This problem was spotted by Lai Jiangshan. v4: destroy_workqueue() was putting wq->dfl_pwq and then clearing it; however, wq may be freed at any time after dfl_pwq is put making the clearing use-after-free. Clear wq->dfl_pwq before putting it. v5: apply_workqueue_attrs() was leaking @tmp_attrs, @new_attrs and @pwq_tbl after success. Fixed. Retry loop in wq_update_unbound_numa_attrs() isn't necessary as application of new attrs is excluded via CPU hotplug. Removed. Documentation on CPU affinity guarantee on CPU_DOWN added. All changes are suggested by Lai Jiangshan. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Diffstat (limited to 'drivers/net/ethernet')
0 files changed, 0 insertions, 0 deletions
OpenPOWER on IntegriCloud