GPT vs MBR for swap devices

Warner Losh imp at
Fri Jun 15 17:21:04 UTC 2018

On Fri, Jun 15, 2018 at 10:42 AM, bob prohaska <fbsd at> 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.


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