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Date:      Fri, 15 Jun 2018 11:21:01 -0600
From:      Warner Losh <imp@bsdimp.com>
To:        bob prohaska <fbsd@www.zefox.net>
Cc:        Mark Millard <marklmi@yahoo.com>, "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org>,  "Rodney W. Grimes" <freebsd-rwg@pdx.rh.cn85.dnsmgr.net>
Subject:   Re: GPT vs MBR for swap devices
Message-ID:  <CANCZdfo8=amqT7M6Xn8NJrW-8spd0XdxjAYjs3F7LVsBUQtpsw@mail.gmail.com>
In-Reply-To: <20180615164202.GB39777@www.zefox.net>
References:  <20180614175622.GC35161@www.zefox.net> <201806142110.w5ELAL0N046840@pdx.rh.CN85.dnsmgr.net> <20180615035225.GA37370@www.zefox.net> <CANCZdfoNasSpvEN-y3bzsDfWT=_atfp62AKvdpwK8bUQKi=bgA@mail.gmail.com> <20180615051527.GB37370@www.zefox.net> <834EA7A6-B567-436F-96B2-0C75FACA3FF9@yahoo.com> <20180615154334.GA39777@www.zefox.net> <CANCZdfoCA=E=Sh2X6H=Fi-TBkhiTdyzXAkjXr4usa8ie6%2Buo4g@mail.gmail.com> <20180615164202.GB39777@www.zefox.net>

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On Fri, Jun 15, 2018 at 10:42 AM, bob prohaska <fbsd@www.zefox.net> wrote:

> On Fri, Jun 15, 2018 at 09:57:17AM -0600, Warner Losh wrote:
>
> > gstat -Bd -I 10 -f <regexp for your swap partition>  >
> gstat-swap-data.dat
> >
> > would be how I'd recommend collecting it. This file may get kinda big
> > depending how long it takes to trigger the weird state. I'm hoping that
> if
> > you put this on a known good device, we'll power through the issues. We
> > might not get perfect correlation with this, but the data should show all
> > kinds of crazy before the system drives off the cliff if I'm right, so we
> > don't need perfect data.
> >
>
> Apologies,  we spoke of gstat earlier. I lost the distinction between
> gstat and vmstat. In the case at hand the possible swap devices are
>
> /dev/da0b (this is the one causing trouble)
> /dev/mmcsd0s3b
> /dev/mmcsd0s3d
>
>
> what would the correct <regexp> look like?
>

I'd just use -f '^da0b$' for each of the devices.


> Is there any indication why problems seen on the RPI3 do not seem
> apparent on an RPI2? A 2 GB USB flash swap partition seems to work
> successfully on the Pi2.
>

Interesting. The only thing I can think of is different OOM tuning levels.
But if anything, I'd expect more trouble on the RPi2 than the RPi3. So that
might also point to a difference in USB and/or VM things. It would be
interesting to see if we see a significant difference in the graphs between
the two for the same physical drive. I'd have expected, like you, that this
would be reproducible between the two.

Warner



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