Re: armv7, silent hang, low swap, high priorities

On Dec 20, 2024, at 09:10, bob prohaska <[email protected]> wrote:

> An old (v 1.1) Pi2 running armv7 -current often hangs during buildworld.
> 
> It doesn't respond to enter-tilda-control-B and has to be powercycled.
> Once rebooted, buildworld can be restarted and makes further progress,
> sometimes to completion. Swap was configured in two partitions, one
> on microSD and one on mechanical hard disk, thus both over-provisioned 
> and wildly unequal in speed. Root is on the mechanical disk. 
> 
> An orphan top window surprised me by reporting very high priorities
> in the 130 range but swap usage was relatively low, less than 100MB.
> That seemed an odd combination. Usually priorities that high are
> associated with severe memory pressure. Could the mismatched swap
> speeds have confused the scheduler? There were no console warnings. 
> 
> The machine was fully loaded with a -j4 buildworld, so the fact of 
> the hang isn't hugely surprising. The top display, at
> http://www.zefox.net/~fbsd/rpi2/crashes/20241219/top_display
> seemed internally inconsitent.  Does it surprise anybody else? 
> 
> I've since removed the microSD swap, leaving only the mechanical disk
> swap, to see if that changes the hang behavior.


QUOTE
. . .
The nice utility runs utility at an altered scheduling priority, by in-
crementing its "nice" value by the specified increment, or a default
value of 10. The lower the nice value of a process, the higher its
scheduling priority.
END QUOTE

Renice, setpriority(), etc. agree.

Those 120+ figures are LOWER priority than the under 100 figures,
not higher.

===
Mark Millard
marklmi at yahoo.com