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Date:   Mon, 10 Nov 2014 18:03:58 +0100
From:   Ralf Baechle <ralf@linux-mips.org>
To:     David Daney <ddaney.cavm@gmail.com>
Cc:     Joshua Kinard <kumba@gentoo.org>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Linux MIPS List <linux-mips@linux-mips.org>
Subject: Re: IP27: CONFIG_TRANSPARENT_HUGEPAGE triggers bus errors
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On Mon, Nov 10, 2014 at 08:55:09AM -0800, David Daney wrote:

> Yes, you may be on to something here.  Certianly basic huge TLB support must
> be in place for TRANSPARENT_HUGEPAGE to work.
> 
> It could be that the Kconfig symbols for the various portions of huge page
> support are missing the required dependencies.
> 
> FWIW, I always build with a huge page Kconfig options set.
> 
> I have:
> $ grep HUGE .config
> CONFIG_SYS_SUPPORTS_HUGETLBFS=y
> CONFIG_MIPS_HUGE_TLB_SUPPORT=y
> CONFIG_CPU_SUPPORTS_HUGEPAGES=y
> CONFIG_TRANSPARENT_HUGEPAGE=y
> CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS=y
> # CONFIG_TRANSPARENT_HUGEPAGE_MADVISE is not set
> CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE=y
> CONFIG_HUGETLBFS=y
> CONFIG_HUGETLB_PAGE=y
> 
> I suspect that you may not need CONFIG_HUGETLBFS, but CONFIG_HUGETLB_PAGE is
> probably essential.

IP27 also has NUMA as the only in-tree MIPS system - and it's NUMA support
is not in the best support state to say the least.  Just an observation -
at this point in time there is no obvious connection between either

  R10000 <-> transparent huge page

or

  NUMA <-> transparent huge page

  Ralf