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Re: abysmally low scp performance

> I'm just scp-ing a multi-gigabyte file from one NetBSD-8 machine to
> another, and get a whopping 10MB/s throughput.

> Interfaces are wm, 1000BaseT (says ifconfig and the switch),connected
> to the same (enterprise) switch.

> Discs are ~20% busy on the receiving end, less on the sending end.
> ssh/sshd are at ~20% CPU max, CPUs are 50% (sending side, which does
> multiple other things)/80% (receiving side, which does nothing) idle.

Depending on what "N% idle" means, the CPU percentage figures may mean
nothing.  Some CPU percentage figures are percentage of all cycles
available, in which case a single-threaded program, even if
CPU-constrained, can't take more than 1/N where N is the number of
cores available.

You don't say which scp implementation you're using, so I would tend to
assume it's the one shipped with the system, meaning an OpenSSH
version.  I don't know OpenSSH all that well, but I suspect it is
single-threaded in the relevant respects.


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