linux-kernel - Re: [PATCH 0/8] THP support for Sparc64

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Date:	Tue, 2 Oct 2012 15:55:44 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	David Miller <davem@...emloft.net>
Cc:	linux-mm@...ck.org, sparclinux@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	aarcange@...hat.com, hannes@...xchg.org,
	Gerald Schaefer <gerald.schaefer@...ibm.com>
Subject: Re: [PATCH 0/8] THP support for Sparc64

On Tue, 02 Oct 2012 18:26:01 -0400 (EDT)
David Miller <davem@...emloft.net> wrote:

> Here is a set of patches that add THP support for sparc64.
> 
> A few of them are relatively minor portability issues I ran into.
> Like the MIPS guys I hit the update_mmu_cache() typing issue so I have
> a patch for that here.
> 
> It is very likely that I need the ACCESSED bit handling fix the
> ARM folks have been posting recently as well.
> 
> On the sparc64 side the biggest issue was moving to only supporting
> 4MB pages and then realigning the page tables so that the PMDs map 4MB
> (instead of 8MB as they do now).
> 
> The rest was just trial and error, running tests, and fixing bugs.
> 
> A familiar test case that makes 5 million random accesses to a 1GB
> memory area goes from 20 seconds down to 0.43 seconds with THP enabled
> on my SPARC T4-2 box.

Hardly worth bothering about ;)

I had a shot at integrating all this onto the pending stuff in linux-next. 
"mm: Add and use update_mmu_cache_pmd() in transparent huge page code."
needed minor massaging in huge_memory.c.  But as Andrea mentioned, we
ran aground on Gerald's
http://ozlabs.org/~akpm/mmotm/broken-out/thp-remove-assumptions-on-pgtable_t-type.patch,
part of the thp-for-s390 work.


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