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From: Adrian Chadd <adrian.chadd@gmail.com>
Date: Wed, 17 Aug 2016 08:38:38 -0700
Message-ID: <CAJ-Vmo=J9GnUYYD7noxvd-RfvXmZn56UYn92wfg8Y3eHUc2-Vg@mail.gmail.com>
Subject: Re: Unstable local network throughput
To: Ben RUBSON <ben.rubson@gmail.com>
Cc: FreeBSD Net <freebsd-net@freebsd.org>
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[snip]

ok, so this is what I was seeing when I was working on this stuff last.

The big abusers are:

* so_snd lock, for TX'ing producer/consumer socket data
* tcp stack pcb locking (which rss tries to work around, but it again
doesn't help producer/consumer locking, only multiple sockets)
* for some of the workloads, the scheduler spinlocks are pretty
heavily contended and that's likely worth digging into.

Thanks! I'll go try this on a couple of boxes I have with
intel/chelsio 40g hardware in it and see if I can reproduce it. (My
test boxes have the 40g NICs in NUMA domain 1...)



-adrian