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Message-ID: <20140124133830.GU4963@suse.de>
Date: Fri, 24 Jan 2014 13:38:30 +0000
From: Mel Gorman <mgorman@...e.de>
To: Elena Ufimtseva <ufimtseva@...il.com>
Cc: Steven Noonan <steven@...inklabs.net>,
Daniel Borkmann <borkmann@...earbox.net>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
David Vrabel <david.vrabel@...rix.com>,
xen-devel <xen-devel@...ts.xenproject.org>,
George Dunlap <george.dunlap@...citrix.com>,
Dario Faggioli <dario.faggioli@...rix.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Andrea Arcangeli <aarcange@...hat.com>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Linux Kernel mailing List <linux-kernel@...r.kernel.org>,
Rik van Riel <riel@...hat.com>,
Alex Thorlton <athorlton@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
Vlastimil Babka <vbabka@...e.cz>,
Michel Lespinasse <walken@...gle.com>
Subject: Re: [BISECTED] Linux 3.12.7 introduces page map handling regression
On Thu, Jan 23, 2014 at 11:23:37AM -0500, Elena Ufimtseva wrote:
> >> >> <SNIP>
> >> >>
> >> >> This dump doesn't look dramatically different, either.
> >> >>
> >> >>>
> >> >>> The other question is - how is AutoNUMA running when it is not enabled?
> >> >>> Shouldn't those _PAGE_NUMA ops be nops when AutoNUMA hasn't even been
> >> >>> turned on?
> >> >>
> >> >>
> >> >> Well, NUMA_BALANCING is enabled in the kernel config[1], but I presume you
> >> >> mean not enabled at runtime?
> >> >>
> >> >> [1]
> >> >> http://git.uplinklabs.net/snoonan/projects/archlinux/ec2/ec2-packages.git/tree/linux-ec2/config.x86_64
> >>
> >>
> >>
> >> --
> >> Elena
>
> I was able to reproduce this consistently, also with the latest mm
> patches from yesterday.
> Can you please try this:
>
Thanks Elena,
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index ce563be..76dcf96 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -365,7 +365,7 @@ void xen_ptep_modify_prot_commit(struct mm_struct
> *mm, unsigned long addr,
> /* Assume pteval_t is equivalent to all the other *val_t types. */
> static pteval_t pte_mfn_to_pfn(pteval_t val)
> {
> - if (val & _PAGE_PRESENT) {
> + if ((val & _PAGE_PRESENT) || ((val &
> (_PAGE_NUMA|_PAGE_PRESENT)) == _PAGE_NUMA)) {
> unsigned long mfn = (val & PTE_PFN_MASK) >> PAGE_SHIFT;
> unsigned long pfn = mfn_to_pfn(mfn);
>
> @@ -381,7 +381,7 @@ static pteval_t pte_mfn_to_pfn(pteval_t val)
>
> static pteval_t pte_pfn_to_mfn(pteval_t val)
> {
> - if (val & _PAGE_PRESENT) {
> + if ((val & _PAGE_PRESENT) || ((val &
> (_PAGE_NUMA|_PAGE_PRESENT)) == _PAGE_NUMA)) {
> unsigned long pfn = (val & PTE_PFN_MASK) >> PAGE_SHIFT;
> pteval_t flags = val & PTE_FLAGS_MASK;
> unsigned long mfn;
Would reusing pte_present be an option? Ordinarily I expect that
PAGE_NUMA/PAGE_PROTNONE is only set if PAGE_PRESENT is not set and pte_present
is defined as
static inline int pte_present(pte_t a)
{
return pte_flags(a) & (_PAGE_PRESENT | _PAGE_PROTNONE |
_PAGE_NUMA);
}
So it looks like it work work. Of course it would need to be split to
reuse it within xen if pte_present was split to have a pteval_present
helper like so
static inline int pteval_present(pteval_t val)
{
/*
* Yes Linus, _PAGE_PROTNONE == _PAGE_NUMA. Expressing it this
* way clearly states that the intent is that a protnone and numa
* hinting ptes are considered present for the purposes of
* pagetable operations like zapping, protection changes, gup etc.
*/
return val & (_PAGE_PRESENT | _PAGE_PROTNONE | _PAGE_NUMA);
}
static inline int pte_present(pte_t pte)
{
return pteval_present(pte_flags(pte))
}
If Xen is doing some other tricks with _PAGE_PRESENT then it might be
ruled out as an option. If so, then maybe it could still be made a
little clearer for future reference?
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index c1d406f..ff621de 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -365,7 +365,7 @@ void xen_ptep_modify_prot_commit(struct mm_struct *mm, unsigned long addr,
/* Assume pteval_t is equivalent to all the other *val_t types. */
static pteval_t pte_mfn_to_pfn(pteval_t val)
{
- if (val & _PAGE_PRESENT) {
+ if ((val & _PAGE_PRESENT) || pteval_numa(val)) {
unsigned long mfn = (val & PTE_PFN_MASK) >> PAGE_SHIFT;
unsigned long pfn = mfn_to_pfn(mfn);
@@ -381,7 +381,7 @@ static pteval_t pte_mfn_to_pfn(pteval_t val)
static pteval_t pte_pfn_to_mfn(pteval_t val)
{
- if (val & _PAGE_PRESENT) {
+ if ((val & _PAGE_PRESENT) || pteval_numa(val)) {
unsigned long pfn = (val & PTE_PFN_MASK) >> PAGE_SHIFT;
pteval_t flags = val & PTE_FLAGS_MASK;
unsigned long mfn;
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 8e4f41d..693fe00 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -654,10 +654,14 @@ static inline int pmd_trans_unstable(pmd_t *pmd)
* (because _PAGE_PRESENT is not set).
*/
#ifndef pte_numa
+static inline int pteval_numa(pteval_t pteval)
+{
+ return (pteval & (_PAGE_NUMA|_PAGE_PRESENT)) == _PAGE_NUMA;
+}
+
static inline int pte_numa(pte_t pte)
{
- return (pte_flags(pte) &
- (_PAGE_NUMA|_PAGE_PRESENT)) == _PAGE_NUMA;
+ return pteval_numa(pte_flags(pte));
}
#endif
--
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