linux-kernel - Re: [PATCH 06/43] mm: numa: Make pte_numa() and pmd

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Message-ID: <20121116160852.GA4302@gmail.com>
Date:	Fri, 16 Nov 2012 17:08:52 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Hugh Dickins <hughd@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 06/43] mm: numa: Make pte_numa() and pmd_numa() a generic
 implementation


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Fri, Nov 16, 2012 at 6:41 AM, Mel Gorman <mgorman@...e.de> wrote:
> >
> > I would have preferred asm-generic/pgtable.h myself and use
> > __HAVE_ARCH_whatever tricks
> 
> PLEASE NO!
> 
> Dammit, why is this disease still so prevalent, and why do people
> continue to do this crap?

Also, why is this done in a weird, roundabout way of first 
picking up a bad patch and then modifying it and making it even 
worse?

Why not use something what we have in numa/core already:

  f05ea0948708 mm/mpol: Create special PROT_NONE infrastructure

AFAICS, this portion of numa/core:

c740b1cccdcb x86/mm: Completely drop the TLB flush from ptep_set_access_flags()
02743c9c03f1 mm/mpol: Use special PROT_NONE to migrate pages
b33467764d8a mm/migrate: Introduce migrate_misplaced_page()
db4aa58db59a numa, mm: Support NUMA hinting page faults from gup/gup_fast
ca2ea0747a5b mm/mpol: Add MPOL_MF_LAZY
f05ea0948708 mm/mpol: Create special PROT_NONE infrastructure
37081a3de2bf mm/mpol: Check for misplaced page
cd203e33c39d mm/mpol: Add MPOL_MF_NOOP
88f4670789e3 mm/mpol: Make MPOL_LOCAL a real policy
83babc0d2944 mm/pgprot: Move the pgprot_modify() fallback definition to mm.h
536165ead34b sched, numa, mm, MIPS/thp: Add pmd_pgprot() implementation
6fe64360a759 mm: Only flush the TLB when clearing an accessible pte
e9df40bfeb25 x86/mm: Introduce pte_accessible()
3f2b613771ec mm/thp: Preserve pgprot across huge page split
a5a608d83e0e sched, numa, mm, s390/thp: Implement pmd_pgprot() for s390
995334a2ee83 sched, numa, mm: Describe the NUMA scheduling problem formally
7ee9d9209c57 sched, numa, mm: Make find_busiest_queue() a method
4fd98847ba5c x86/mm: Only do a local tlb flush in ptep_set_access_flags()
d24fc0571afb mm/generic: Only flush the local TLB in ptep_set_access_flags()

is a good foundation already with no WIP policy bits in it.

Mel, could you please work on this basis, or point out the bits 
you don't agree with so I can fix it?

Since I'm working on improving the policy bits I essentially 
need and have done all the 'foundation' work already - you might 
as well reuse it as-is instead of rebasing it?

Thanks,

	Ingo
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