GPT vs MBR for swap devices

[Rodney W. Grimes]

> On Thu, Jun 14, 2018 at 09:53:57AM -0700, Rodney W. Grimes wrote:
> > 
> > I would be very interested in seeing if resizing the swap partition
> > in the example that greatly exceeds what the system expects as a
> > max total swap helps to bring the OOM issue under control.
> > 
> The swap partitions at my immediate disposal are
> 1 GB USB flash
> 1 GB microSD flash
> 2 GB microSD flash
> 3 GB USB mechanical
> 
> What combination is apt to be most informative? My original intent
> was to use 1 GB USB flash plus 1 GB microSD flash in hopes of a speed
> gain from interleaving, but maybe that's no longer realistic. Anything
> over 3 GB total causes the "too much swap" warning and I've never observed
> more than about 1.2 GB of swap in use.

Well if you do a swapon to the 3 GB USB Mechanical that
should be all that is usable, so we could infact test
the theory by doing that one first and adding
anything to it and find out if it started to
use the others.
Or someone that knows the current code could tell us :-)

It might be interesting to do in order the swapon
commands to 1G USB flash, 1G SD flash, 2G SD flash,
that should if what I think happens yeild a pretty
even 1G of each usable, with 1G wasted on the 2G SD flash.


> > I think the state of things is such that if you use up the
> > max usable swap space on the first swap device, only that
> > swap device well ever be used.  I do not believe there is
> > any attempts what so ever to split the allocation up so
> > that you use the first fraction of each device.
> > 
> 
> Swap usage seem to be spread among active partitions, though 
> how they're weighted is unclear to me. In days of yore there
> was a little note about "interleaved" in swapinfo reports, but
> I don't recall seeing that for a loong time. Maybe that feature
> has gone away.....
> 
> Thanks for reading,
> 
> bob prohaska
> 
> 
> 
> 

-- 
Rod Grimes                                                 rgrimes at freebsd.org