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Re: MIPS: Add dependencies for HAVE_ARCH_TRANSPARENT_HUGEPAGE

To: linux-mips@linux-mips.org
Subject: Re: MIPS: Add dependencies for HAVE_ARCH_TRANSPARENT_HUGEPAGE
From: Sebastian Gottschall <s.gottschall@dd-wrt.com>
Date: Wed, 20 Mar 2013 23:33:36 +0100
In-reply-to: <1362370641.3768.291.camel@deadeye.wl.decadent.org.uk>
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Am 04.03.2013 05:17, schrieb Ben Hutchings:
The MIPS implementation of transparent huge-pages (THP) is 64-bit only,
and of course also requires that the CPU supports huge-pages.

Currently it's entirely possible to enable THP in other configurations,
which then fail to build due to pfn_pmd() not being defined.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: David Daney <david.daney@cavium.com>
---
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -19,7 +19,7 @@ config MIPS
        select HAVE_KRETPROBES
        select HAVE_DEBUG_KMEMLEAK
        select ARCH_BINFMT_ELF_RANDOMIZE_PIE
-       select HAVE_ARCH_TRANSPARENT_HUGEPAGE
+       select HAVE_ARCH_TRANSPARENT_HUGEPAGE if CPU_SUPPORTS_HUGEPAGES && 64BIT
        select RTC_LIB if !MACH_LOONGSON
        select GENERIC_ATOMIC64 if !64BIT
        select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE

why? the mips32 74k platform (broadcom bcm4706 for instance) does support huge pages. and some of these devices are also using highmem for accessing more than 128mb ram (which is totally broken in all current kernels too and causing filesystem corruptions) i was able to fix the highmem problem using a patch which was submitted but never taken into the mainline, but i just was able to get thb partially to work on mips32. but i think it would be possible to support this on mips32 as well. so why leaving it out?

regards,
Sebastian Gottschall


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