GPT vs MBR for swap devices

[bob prohaska]

On Thu, Jun 14, 2018 at 11:37:48PM -0700, Mark Millard wrote:
> 
> When I look at:
> 
> # vmstat -c -w 5
> procs  memory       page                    disks     faults         cpu
> r b w  avm   fre   flt  re  pi  po    fr   sr da0 ad0   in    sy    cs us sy id
> 1 0 0 416M  224M  1647   1   0   0  1856  142   0   0  144  1791  1024  4  2 94
> 0 0 0 416M  224M     9   0   0   0     0    1   0   0    4    85   116  0  0 100
> 0 0 0 416M  224M    12   0   0   0     0    1   0   0    2    93   113  0  0 100
> 0 0 0 416M  224M     9   0   0   0     2    1   1   0    4    64   121  0  0 100
> . . .
> 
> and "man vmstat" I do not see any column that is the swap space
> usage (nor any combination of columns to do such a calculation
> from).
> 
> I do not expect that vmstat reports what you are likely/primarily
> looking for.
> 
> An example is "avm" which for which the man page reports:
> 
>              . . . Note that the entire
>              memory object's size is considered mapped even if only a subset
>              of the object's pages are currently mapped.  This statistic is
>              not related to the active page queue which is used to track real
>              memory.
> 
> The free list size ("fre") is not sufficient either.
> 

That seems astonishing. I imagined that among those columns _had_ to be
reads from and writes to the swap partitions. 

It looks as if 
top -d 1000 | grep Swap
produces a running list of swap usage, but one must guess how many
times to iterate:
 
bob at www:/usr/src % top -d 1000 | grep Swap
Swap: 3072M Total, 30M Used, 3041M Free
Swap: 3072M Total, 30M Used, 3041M Free
Swap: 3072M Total, 30M Used, 3041M Free
Swap: 3072M Total, 30M Used, 3041M Free
Swap: 3072M Total, 30M Used, 3041M Free
.......

Replacing the "1000" with "0" or "infinite" triggers
a syntax error. Is there a special parameter that makes top run till 
it's killed, as in interactive mode? I didn't recognize any hint in the
man page.

Thanks for reading!

bob prohaska