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Currently scheduler threads are grouped into blocks, ksock_sched_info divided by the number of configured CPTs. Each ksock_sched_info defaults to having cfs_cpt_weight() threads struct ksock_sched, or if ksnd_nscheds is configured, it will select the least of these. The idea is not to have more threads than the cfs_cpt_weight().
A struct ksock_sched is associated with exactly 1 thread. There is a 1:1 relationship between a ksock_sched and a scheduler thread. So any transmits or receives queued on the ksock_sched will be served by that thread.
When creating a connection the connection is associated with a thread a ksock_sched selected from the ksock_sched_info on the CPT derived by lnet_cpt_of_nid(peer_nid).
The connection remains associated with that thread that ksock_sched for the duration of its life.
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The life span of a TCP connection spans multiple transmits/receives. This means that the same scheduler thread is used for all these transmitsoperations. The scheduler is changed only when the connection is torn down. In an lnet_selftest run and in other filesystem tests one scheduler thread takes up all the CPU resources, causing severe drop in performance.
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