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Reduce contention on per-adapter lock.

Authored by jhb on Jun 25 2020, 9:24 PM.


  • Move temporary sglists into the session structure and protect them with a per-session lock instead of a per-adapter lock.
  • Retire an unused session field, and move a debugging field under INVARIANTS to avoid using the session lock for completion handling when INVARIANTS isn't enabled.
  • Use counter_u64 for per-adapter statistics.

Note that this helps for cases where multiple sessions are used
(e.g. multiple IPsec SAs or multiple KTLS connections). It does not
help for workloads that use a single session (e.g. a single GELI

Test Plan
  • tested with KTLS RX where it made a marginal perf improvement (29 Gbps to 30-31 Gbps). However, in pmcstat callchains, lock_delay due to lock contention went from 6% of overall time (of which 82% was for the adapter lock in ccr_process) to 3% of overall time (of which 3% was for the per-session lock in ccr_process)

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Build Status
Buildable 31967
Build 29516: arc lint + arc unit