i386 PAE kernel works fine on 10-stable

[Peter Wemm]

On Monday, December 15, 2014 05:12:39 PM Adrian Chadd wrote:
> On 15 December 2014 at 16:33, Alfred Perlstein <bright at mu.org> wrote:
> >> On Dec 15, 2014, at 3:42 PM, Peter Wemm <peter at wemm.org> wrote:
> >> 
> >> It's always been a 1GB/3GB split.  It was never a problem until certain
> >> scaling defaults were changed to scale solely based on physical ram
> >> without
> >> regard for kva limits.
> > 
> > Hmm the original patch I gave for that only changed scaling for machines
> > with 64 bit pointers. Why was it that the 32 bit stuff was made to
> > change?
> I recall this - I went digging; commit
> 
> 7beb738c8a72cc197d3e898784afe3fba28f1834
> 
> removed that particular bit of autotuning based on the size of void *.
> 
> Maybe this stuff is a little busted and we need to add some more
> config parameters?
> 
> (Also, there's the vm space shift thing that also needed adjustment
> for memory-constrained systems. We've had do it on MIPS and low-memory
> (64mb, 128mb) RAM i386 systems.)
> 
> 
> 
> -adrian

There's more to it than just one commit.  There's years of general trends that 
added scaling by physical ram without regard for kva consumption.  The 
starting point for Alfred's commits a few years ago already didn't work 
properly on large memory systems.  Alfred worked on the scaling for the 64-bit 
/ direct map systems and tried to leave the caps alone for kva-constrained 
systems.  The caps were already too high.

Except for i386, kva-limited systems generally are pretty small and are 
explicitly tuned for "small".  The tuning considerations for a 32MB or 64MB 
mips/arm system is very different than a 16GB i386 PAE system.

-- 
Peter Wemm - peter at wemm.org; peter at FreeBSD.org; peter at yahoo-inc.com; KI6FJV
UTF-8: for when a ' or ... just won\342\200\231t do\342\200\246
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