Re: nmbclusters on amd64

[Stephen Borrill <netbsd%precedence.co.uk@localhost>]

On Wed, 24 Aug 2016, Joerg Sonnenberger wrote:
> On Wed, Aug 24, 2016 at 01:54:19PM +0100, Stephen Borrill wrote:
> > Machine in question has 16GB RAM and is running amd64. Reading further, it
> > looks like setting NMBCLUSTERS in netbsd-7 as a compile-time option is only
> > capable of limiting the number which is generally counterproductive:
>
> Looking at one of my build VMs running 7.0 with 16GB, auto-scaling
> gives:
> kern.mbuf.nmbclusters = 524274
>
> > #ifdef NMBCLUSTERS_MAX
> >         max_size = MIN(max_size, NMBCLUSTERS_MAX);
> > #endif
> >
> > #ifdef NMBCLUSTERS
> >         return MIN(max_size, NMBCLUSTERS);
> > #else
> >         return max_size;
> > #endif
> >
> > Perhaps this should have been MAX(max_size, NMBCLUSTERS) which makes more
> > sense to me.
>
> No, the intention is to compute the limit of what the system ressources
> can sustain and cap at that.

I get that, but setting NMBCLUSTERS now limits nmbclusters to some number 
below the computed limit. With -5 and earlier it raised it from a low 
limit (1024 if GATEWAY was set) and so it was pretty much required for any 
sensible work. I guess the take-home message is now "NMBCLUSTERS is bad, 
do not use it".

--
Stephen