CVS commit: src/sys/net

["Taylor R Campbell" <riastradh%netbsd.org@localhost>]

Module Name:    src
Committed By:   riastradh
Date:           Mon Sep  7 01:15:25 UTC 2020

Modified Files:
        src/sys/net: if_wg.c

Log Message:
wg: Use threadpool(9) and workqueue(9) for asynchronous tasks.

- Using threadpool(9) job per interface to receive incoming handshake
  messages gives the same concurrency for active interfaces but
  doesn't waste kthreads for inactive ones.

  => Can't really do this with a global workqueue(9) because there's
     no bound on the amount of time wg_receive_packets() might run
     for; we really need separate threads or threadpool jobs in order
     to avoid having one interface starve all the others.

- Using a global workqueue(9) for asynchronous peer tasks avoids
  creating unnecessary kthreads.

  => Each task does a more or less bounded amount of work, so it's OK
     to share a global workqueue -- there's no advantage to adding
     concurrency for what is almost certainly going to be CPU-bound
     asymmetric crypto.

  => This way we don't need a thread per peer or iteration over a
     list of all peers, so the task mechanism should no longer be a
     bottleneck to scaling to thousands of peers.

XXX This doesn't distribute the load across CPUs -- it keeps it on
the same CPU where the packet came in.  Should consider doing
something to balance the load -- maybe note if the current CPU is
loaded, and if so, sort CPUs by queue length or some other measure of
load and pick the least loaded one or something.


To generate a diff of this commit:
cvs rdiff -u -r1.54 -r1.55 src/sys/net/if_wg.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.