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Date:      Thu, 08 Aug 2013 07:04:37 -0600
From:      Ian Lepore <ian@FreeBSD.org>
To:        Krister Olofsson <krister.olofsson@gmail.com>
Cc:        freebsd-arm@FreeBSD.org
Subject:   Re: System freezes when using scp
Message-ID:  <1375967077.3320.117.camel@revolution.hippie.lan>
In-Reply-To: <CAAY5Z-M%2BS1VhNBerTOjnTSisa1n-DgD-gTsymSTayZ-QosMMzA@mail.gmail.com>
References:  <CAAY5Z-M%2BS1VhNBerTOjnTSisa1n-DgD-gTsymSTayZ-QosMMzA@mail.gmail.com>

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On Thu, 2013-08-08 at 13:44 +0200, Krister Olofsson wrote:
> Hi,
> 
> I'm working with a board with FreeBSD 8.2 on Marvell MV78100 (Discovery
> SOC) - an ARMv5TE and Marvell Gigabit Ethernet controller.
> My problem is that when I copy files (size ca 50 Mb) with scp using
> ethernet, the system
> seems to freeze for a few seconds before the copy process starts.
> The board has an external watchdog that has to be kicked but the script
> doing this freezes and the system is rebooted by the watchdog.
> 
> Any ideas how to tackle this?
> 
> Regards,
> Krister
> 
> Configuration:
> 
> #
> # Custom kernel for PROJ, based on Marvell's DB-78xx
> #
> [...]

Do you get the same kind of pause interactively ssh'ing to it?  When you
say "a few seconds" what do you mean?  3 seconds?  8?  30?

I think a good first step is to figure out whether the problem is
related to ssh, or network IO, or disk IO.  You can take ssh out of the
picture by using netcat to test, something like:

 On the arm:  nc -l 8000 >/output/file
 On the sender: nc <ip of arm> 8000 </input/file

If you send the output to /dev/null on the arm you're just testing the
network part.  

In my experience, a long pause at the start of an ssh session followed
by normal performance after that is what you get when a wimpy arm chip
with software floating point generates the session keys.  But that's
based on experience with a 180mhz armv4 chip.  I've never noticed that
sort of slowness on my DreamPlug (1.2ghz Marvell Kirkwood chips).

-- Ian





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