Builworld stalls on rpi2 [various processes stuck in pfault and vmwait with 1996M Free Swap listed by top]

[Mark Millard]

On 2018-Jan-13, at 9:27 AM, bob prohaska <fbsd at www.zefox.net> wrote:

> On Sat, Jan 13, 2018 at 08:32:20AM -0800, Mark Millard wrote:
>> Does your 2 GiByte swap-space RPi2 "dmesg -a" output
>> (or serial console history) show any messages about the
>> swap-space size and a potential adjustment to a related
>> kernel parameter?
>> 
> Yes, console history contains the line
> 
> warning: total configured swap (524288 pages) exceeds maximum recommended amount (405460 pages).
> 
> Since top reported what looked like ample swap, and buildworld seemed to
> run successfully, I didn't heed the
> 
> warning: increase kern.maxswzone or reduce amount of swap.
> 
> message. 
> 
> Would it be helpful to do so now? gpart show da0 reports
> 
> =>        0  122544516  da0  BSD  (58G)
>          0    4194304    1  freebsd-ufs  (2.0G)
>    4194304    4194304    2  freebsd-swap  (2.0G)
>    8388608    6291456    4  freebsd-ufs  (3.0G)
>   14680064  107864452    5  freebsd-ufs  (51G)
> 
> The units are somewhat baffling, since the apparent swap partition
> size does not match (numerically) the dmesg value.

[gpart is showing in 512 Byte units, probably matching
a drive-organization characteristic.]

page = 4 KiBytes
So 405460 pages = 1621840 KiBytes, so a little over 1.54 GiBytes.

For reference:
524288 pages = 2097152 KiBytes, so exactly 2.0 GiBytes.

Note: 2*2097152 == 4194304 exactly, so the 512 Byte count
is an exact match to the 2.0 GiByte swap size.

When there is only 1 GiByte of RAM, I'm not sure if increasing
kern.maxswzone is a good tradeoff or not.

Historically I've kept the swap space within the recommended
maximum for the default kern.maxswzone value. But for the RPi2B
V1.1 context, I've not tried a self-hosted buildworld in a
long time, doing cross builds instead.

===
Mark Millard
markmi at dsl-only.net