From: Linus Torvalds <torvalds@linux-foundation.org>
To: Mel Gorman <mgorman@suse.de>
Cc: Dave Chinner <david@fromorbit.com>,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
xfs@oss.sgi.com, ppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH 3/4] mm: numa: Mark huge PTEs young when clearing NUMA hinting faults
Date: Sat, 7 Mar 2015 10:33:43 -0800 [thread overview]
Message-ID: <CA+55aFwSQgrYqfXPr6RPvQ+8OJfexXJRY_GVEKg5QtB2t38cWA@mail.gmail.com> (raw)
In-Reply-To: <1425741651-29152-4-git-send-email-mgorman@suse.de>
On Sat, Mar 7, 2015 at 7:20 AM, Mel Gorman <mgorman@suse.de> wrote:
> pmd = pmd_modify(pmd, vma->vm_page_prot);
> + pmd = pmd_mkyoung(pmd);
Hmm. I *thought* this should be unnecessary. vm_page_prot alreadty has
the accessed bit set, and we kind of depend on the initial page table
setup and mk_pte() and friends (ie all new pages are installed
"young").
But it looks like I am wrong - the way we use _[H]PAGE_CHG_MASK means
that we always take the accessed and dirty bits from the old entry,
ignoring the bit in vm_page_prot.
I wonder if we should just make pte/pmd_modify() work the way I
*thought* they worked (remove the masking of vm_page_prot bits).
So the patch isn't wrong. It's just that we *migth* instead just do
something like this:
arch/x86/include/asm/pgtable.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index a0c35bf6cb92..79b898bb9e18 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -355,7 +355,7 @@ static inline pte_t pte_modify(pte_t pte,
pgprot_t newprot)
* the newprot (if present):
*/
val &= _PAGE_CHG_MASK;
- val |= massage_pgprot(newprot) & ~_PAGE_CHG_MASK;
+ val |= massage_pgprot(newprot);
return __pte(val);
}
@@ -365,7 +365,7 @@ static inline pmd_t pmd_modify(pmd_t pmd,
pgprot_t newprot)
pmdval_t val = pmd_val(pmd);
val &= _HPAGE_CHG_MASK;
- val |= massage_pgprot(newprot) & ~_HPAGE_CHG_MASK;
+ val |= massage_pgprot(newprot);
return __pmd(val);
}
instead, and remove the mkyoung. Completely untested, but that "just
or in the new protection bits" is what pnf_pte() does just a few lines
above this.
Linus
next prev parent reply other threads:[~2015-03-07 18:33 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-07 15:20 [RFC PATCH 0/4] Automatic NUMA balancing and PROT_NONE handling followup v2r8 Mel Gorman
2015-03-07 15:20 ` [PATCH 1/4] mm: thp: Return the correct value for change_huge_pmd Mel Gorman
2015-03-07 20:13 ` Linus Torvalds
2015-03-07 20:31 ` Linus Torvalds
2015-03-07 20:56 ` Mel Gorman
2015-03-07 15:20 ` [PATCH 2/4] mm: numa: Remove migrate_ratelimited Mel Gorman
2015-03-07 15:20 ` [PATCH 3/4] mm: numa: Mark huge PTEs young when clearing NUMA hinting faults Mel Gorman
2015-03-07 18:33 ` Linus Torvalds [this message]
2015-03-07 18:42 ` Linus Torvalds
2015-03-07 15:20 ` [PATCH 4/4] mm: numa: Slow PTE scan rate if migration failures occur Mel Gorman
2015-03-07 16:36 ` Ingo Molnar
2015-03-07 17:37 ` Mel Gorman
2015-03-08 9:54 ` Ingo Molnar
2015-03-07 19:12 ` Linus Torvalds
2015-03-08 10:02 ` Ingo Molnar
2015-03-08 18:35 ` Linus Torvalds
2015-03-08 18:46 ` Linus Torvalds
2015-03-09 11:29 ` Dave Chinner
2015-03-09 16:52 ` Linus Torvalds
2015-03-09 19:19 ` Dave Chinner
2015-03-10 23:55 ` Linus Torvalds
2015-03-12 13:10 ` Mel Gorman
2015-03-12 16:20 ` Linus Torvalds
2015-03-12 18:49 ` Mel Gorman
2015-03-17 7:06 ` Dave Chinner
2015-03-17 16:53 ` Linus Torvalds
2015-03-17 20:51 ` Dave Chinner
2015-03-17 21:30 ` Linus Torvalds
2015-03-17 22:08 ` Dave Chinner
2015-03-18 16:08 ` Linus Torvalds
2015-03-18 17:31 ` Linus Torvalds
2015-03-18 22:23 ` Dave Chinner
2015-03-19 14:10 ` Mel Gorman
2015-03-19 18:09 ` Linus Torvalds
2015-03-19 21:41 ` Linus Torvalds
2015-03-19 22:41 ` Dave Chinner
2015-03-19 23:05 ` Linus Torvalds
2015-03-19 23:23 ` Dave Chinner
2015-03-20 0:23 ` Dave Chinner
2015-03-20 1:29 ` Linus Torvalds
2015-03-20 4:13 ` Dave Chinner
2015-03-20 17:02 ` Linus Torvalds
2015-03-23 12:01 ` Mel Gorman
2015-03-20 10:12 ` Mel Gorman
2015-03-20 9:56 ` Mel Gorman
2015-03-08 20:40 ` Mel Gorman
2015-03-09 21:02 ` Mel Gorman
2015-03-10 13:08 ` Mel Gorman
2015-03-08 9:41 ` Ingo Molnar
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