contigmalloc problem in SMP

[Andrew Reilly]

I reported, earlier, that I wasn't able to get the amd64 version
of the (closed source) 4front-tech OSS driver to start: it was
unable to allocate some contiguous memory (48k or so, at the
time).  I've been in e-mail contact with one of their
developers, and he has released a new version of the driver that
doesn't try to allocate so much memory (now about 28k) for me to
try.  This didn't work either.

However: I've just tried re-booting with
kern.smp.disabled="1"
in /boot/loader.conf, and lo: it works.

So: why might contigmalloc() be failing, in a two-processor
situation?

(Sorry, uname -a:
FreeBSD duncan.reilly.home 6.1-PRERELEASE FreeBSD 6.1-PRERELEASE
#0: Thu Feb  2 16:39:13 EST 2006
root at duncan.reilly.home:/usr/obj/usr/src/sys/DUNCAN  amd64
)

Further details: unlike most other uses of contigmalloc() that I've
seen in the tree (which use PAGE_SIZE alignment), this particular
sound card needs a 64k-aligned buffer, and (with a bit of disassembly)
that's what the oss driver appears to be asking for.  All of the
other arguments look the same.

Oh: while I was looking at /src/sys/vm/vm_contig.c to see if I could
see any obvious causes, I noticed that there's a sysctl knob:
vm.old_contigmalloc, which is defaulting to 0.  I frobbed it to 1
(in loader.conf, and rebooted), and that didn't help (in two-processor
SMP).  Any thoughts on what new vs old contigmalloc entails?

Cheers,

-- 
Andrew