Re: spurious out of swap kills

On Thu, Sep 12, 2019 at 04:00:17PM -0700, Don Lewis wrote:
> My poudriere machine is running 13.0-CURRENT and gets updated to the
> latest version of -CURRENT periodically.  At least in the last week or
> so, I've been seeing occasional port build failures when building my
> default set of ports, and I finally had some time to do some
> investigation.
> 
> It's a 16-thread Ryzen machine, with 64 GB of RAM and 40 GB of swap.
> Poudriere is configured with
>   USE_TMPFS="wrkdir data localbase"
> and I have
>   .if ${.CURDIR:M*/www/chromium}
>   MAKE_JOBS_NUMBER=16
>   .else
>   MAKE_JOBS_NUMBER=7
>   .endif
> in /usr/local/etc/poudriere.d/make.conf, since this gives me the best
> overall build time for my set of ports.  This hits memory pretty hard,
> especially when chromium, firefox, libreoffice, and both versions of
> openoffice are all building at the same time.  During this time, the
> amount of space consumed by tmpfs for /wrkdir gets large when building
> these large ports.  There is not enough RAM to hold it all, so some of
> the older data spills over to swap.  Swap usage peaks at about 10 GB,
> leaving about 30 GB of free swap.  Nevertheless, I see these errors,
> with rustc being the usual victim:
> 
> Sep 11 23:21:43 zipper kernel: pid 16581 (rustc), jid 43, uid 65534, was killed: out of swap space
> Sep 12 02:48:23 zipper kernel: pid 1209 (rustc), jid 62, uid 65534, was killed: out of swap space
> 
> Top shows the size of rustc being about 2 GB, so I doubt that it
> suddenly needs an additional 30 GB of swap.
> 
> I'm wondering if there might be a transient kmem shortage that is
> causing a malloc(..., M_NOWAIT) failure in the swap allocation path
> that is the cause of the problem.

Perhaps this is a consequence of r351114?  To confirm this, you might
try increasing the value of vm.pfault_oom_wait to a larger value, like
20 or 30, and see if the OOM kills still occur.