From owner-freebsd-mips@FreeBSD.ORG  Sat Sep  6 22:24:12 2014
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Subject: bug 193400: sfbuf changes on mips32 may have exposed some vm/pmap
 issues on mips32?
From: Adrian Chadd <adrian@freebsd.org>
To: "freebsd-mips@freebsd.org" <freebsd-mips@freebsd.org>,
 Alan Cox <alc@freebsd.org>, Gleb Smirnoff <glebius@freebsd.org>
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Hi!

This bug:

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=193400

is what I reported to alc a couple weeks ago as breaking on my 128mb
RAM mipsbe board.

It turns out that the difference between the MIPS32 sfbuf code and the
new stuff gleb added was the refcounting side of things. With the MIPS
code, there was no refcounting at all - each sfbuf allocation would
allocate a new sfbuf. Now, I don't know how correct that is (my
reading of the code is "not correct!") but it wasn't panicing things.

So I think maybe gleb's patch to sfbuf exposed a MIPS32 pmap/VM bug?

Alan - how would we go about figuring out what could be the issue here?

I'd really appreciate some help here as I'd like to keep the MIPS32
stuff in good shape. :)

Thanks!


-a