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Date:      Wed, 15 Aug 2018 15:55:04 -0700
From:      bob prohaska <fbsd@www.zefox.net>
To:        Warner Losh <imp@bsdimp.com>
Cc:        Mark Millard <marklmi@yahoo.com>, freebsd-arm <freebsd-arm@freebsd.org>, Mark Johnston <markj@freebsd.org>, bob prohaska <fbsd@www.zefox.net>
Subject:   Re: RPI3 swap experiments (grace under pressure)
Message-ID:  <20180815225504.GB59074@www.zefox.net>
In-Reply-To: <CANCZdfoB_AcidFpKT_ZmZWUFnmC4Bw55krK%2BMqEmmj=f9KMQ2Q@mail.gmail.com>
References:  <B81E53A9-459E-4489-883B-24175B87D049@yahoo.com> <20180813021226.GA46750@www.zefox.net> <0D8B9A29-DD95-4FA3-8F7D-4B85A3BB54D7@yahoo.com> <FC0798A1-C805-4096-9EB1-15E3F854F729@yahoo.com> <20180813185350.GA47132@www.zefox.net> <FA3B8541-73E0-4796-B2AB-D55CE40B9654@yahoo.com> <20180814014226.GA50013@www.zefox.net> <CANCZdfqFKY3Woa%2B9pVS5hika_JUAUCxAvLznSS4gaLq2kKoWtQ@mail.gmail.com> <20180815013612.GB51051@www.zefox.net> <CANCZdfoB_AcidFpKT_ZmZWUFnmC4Bw55krK%2BMqEmmj=f9KMQ2Q@mail.gmail.com>

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On Tue, Aug 14, 2018 at 10:26:39PM -0600, Warner Losh wrote:
[eloquent VM discussion snipped]

> So I think what's well tuned for the gear that's in a server doing
> traditional database and/or compute workloads may not be so well tuned for
> the RPi3 when you put NAND that can vary a lot in performance, as well as
> have fast reads and slow writes when the mix isn't that high. The system
> can be tuned to cope, but isn't tuned that way out of the box.
> 
> tl;dr: these systems are enough different than the normal system that
> additional tuning is needed where the normal systems work great out of the
> box. Plus some code tuneups may help the algorithms be more dynamic than
> they are today.
> 

When I started this goose chase, after zero problems with RPI2, I thought the
issue was arm64-related and might be of some fundamental importance.

Thanks to many people I now understand it's a confluence of USB and flash memory
artifacts, made evident by the demands of clang6. Elsewhere I noted that I'm seeking
"the robustness of a Mars rover, using a rack server OS on a cellphone motherboard".

8-) 

With my thanks to all for much patient good counsel,

bob prohaska




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