[PATCH] smaps should deal with huge zero page exactly same as normal zero page

[PATCH] smaps should deal with huge zero page exactly same as normal zero page

[Fengwei Yin]

[-- Attachment #1: Type: text/plain, Size: 582 bytes --]

Hi,
Fengguang found that the RSS/PSS shown in smaps is not correct
if the file is /dev/zero.

Example:
7bea458b3000-7fea458b3000 r--p 00000000 00:13 39989
  /dev/zero
Size:           4294967296 kB
Rss:            10612736 kB
Pss:            10612736 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:  10612736 kB
Private_Dirty:         0 kB
Referenced:     10612736 kB
Anonymous:             0 kB
AnonHugePages:  10612736 kB
Swap:                  0 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Locked:                0 kB
VmFlags: rd mr mw me

[-- Attachment #2: 0001-smaps-should-deal-with-huge-zero-page-exactly-same.patch --]
[-- Type: application/octet-stream, Size: 2225 bytes --]

From 5e861d550f851040c4d0458ebd3f0fd8fe94dadd Mon Sep 17 00:00:00 2001
From: Fengwei Yin <yfw.kernel@gmail.com>
Date: Thu, 9 Oct 2014 22:20:58 +0800
Subject: [PATCH] smaps should deal with huge zero page exactly same as normal
 zero page.

Signed-off-by: Fengwei Yin <yfw.kernel@gmail.com>
---
 fs/proc/task_mmu.c      | 5 +++--
 include/linux/huge_mm.h | 4 ++++
 mm/huge_memory.c        | 4 ++--
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 80ca4fb..8550b27 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -476,7 +476,7 @@ static void smaps_pte_entry(pte_t ptent, unsigned long addr,
 			mss->nonlinear += ptent_size;
 	}
 
-	if (!page)
+	if (!page || is_huge_zero_page(page))
 		return;
 
 	if (PageAnon(page))
@@ -516,7 +516,8 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 	if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
 		smaps_pte_entry(*(pte_t *)pmd, addr, HPAGE_PMD_SIZE, walk);
 		spin_unlock(ptl);
-		mss->anonymous_thp += HPAGE_PMD_SIZE;
+		if (!is_huge_zero_pmd(*pmd))
+			mss->anonymous_thp += HPAGE_PMD_SIZE;
 		return 0;
 	}
 
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 63579cb..758f569 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -34,6 +34,10 @@ extern int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 			unsigned long addr, pgprot_t newprot,
 			int prot_numa);
 
+extern bool is_huge_zero_page(struct page *page);
+
+extern bool is_huge_zero_pmd(pmd_t pmd);
+
 enum transparent_hugepage_flag {
 	TRANSPARENT_HUGEPAGE_FLAG,
 	TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d9a21d06..bedc3ae 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -173,12 +173,12 @@ static int start_khugepaged(void)
 static atomic_t huge_zero_refcount;
 static struct page *huge_zero_page __read_mostly;
 
-static inline bool is_huge_zero_page(struct page *page)
+bool is_huge_zero_page(struct page *page)
 {
 	return ACCESS_ONCE(huge_zero_page) == page;
 }
 
-static inline bool is_huge_zero_pmd(pmd_t pmd)
+bool is_huge_zero_pmd(pmd_t pmd)
 {
 	return is_huge_zero_page(pmd_page(pmd));
 }
-- 
2.0.1

Re: [PATCH] smaps should deal with huge zero page exactly same as normal zero page

[Dave Hansen]

On 10/09/2014 02:19 AM, Fengwei Yin wrote:
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 80ca4fb..8550b27 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -476,7 +476,7 @@ static void smaps_pte_entry(pte_t ptent, unsigned long addr,
>  			mss->nonlinear += ptent_size;
>  	}
>  
> -	if (!page)
> +	if (!page || is_huge_zero_page(page))
>  		return;

This really seems like a bit of a hack.  A normal (small) zero page
won't make it to this point because of the vm_normal_page() check in
smaps_pte_entry() which hits the _PAGE_SPECIAL bit in the pte.

Is there a reason we can't set _PAGE_SPECIAL on the huge_zero_page ptes?
 If we did that, we wouldn't need a special case here.

If we can't do that for some reason, can we at least teach
vm_normal_page() about the huge_zero_page in some other way?

>  	if (PageAnon(page))
> @@ -516,7 +516,8 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
>  	if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
>  		smaps_pte_entry(*(pte_t *)pmd, addr, HPAGE_PMD_SIZE, walk);
>  		spin_unlock(ptl);
> -		mss->anonymous_thp += HPAGE_PMD_SIZE;
> +		if (!is_huge_zero_pmd(*pmd))
> +			mss->anonymous_thp += HPAGE_PMD_SIZE;
>  		return 0;
>  	}

How about we just move this hunk in to smaps_pte_entry()?  Something
along these lines:

...
        if (PageAnon(page)) {
                mss->anonymous += ptent_size;
+		if (PageTransHuge(page))
+			mss->anonymous_thp += ptent_size;
	}

If we do that, plus teaching vm_normal_page() about huge_zero_pages, it
will help keep the hacks and the extra code due to huge pages to a miniumum.

> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 63579cb..758f569 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -34,6 +34,10 @@ extern int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
>  			unsigned long addr, pgprot_t newprot,
>  			int prot_numa);
>  
> +extern bool is_huge_zero_page(struct page *page);
> +
> +extern bool is_huge_zero_pmd(pmd_t pmd);
> +
>  enum transparent_hugepage_flag {
>  	TRANSPARENT_HUGEPAGE_FLAG,
>  	TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index d9a21d06..bedc3ae 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -173,12 +173,12 @@ static int start_khugepaged(void)
>  static atomic_t huge_zero_refcount;
>  static struct page *huge_zero_page __read_mostly;
>  
> -static inline bool is_huge_zero_page(struct page *page)
> +bool is_huge_zero_page(struct page *page)
>  {
>  	return ACCESS_ONCE(huge_zero_page) == page;
>  }
>  
> -static inline bool is_huge_zero_pmd(pmd_t pmd)
> +bool is_huge_zero_pmd(pmd_t pmd)
>  {
>  	return is_huge_zero_page(pmd_page(pmd));
>  }

^^^ And all these exports.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] smaps should deal with huge zero page exactly same as normal zero page

[Fengwei Yin]

On Thu, Oct 09, 2014 at 09:36:30AM -0700, Dave Hansen wrote:
> On 10/09/2014 02:19 AM, Fengwei Yin wrote:
> > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > index 80ca4fb..8550b27 100644
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -476,7 +476,7 @@ static void smaps_pte_entry(pte_t ptent, unsigned long addr,
> >  			mss->nonlinear += ptent_size;
> >  	}
> >  
> > -	if (!page)
> > +	if (!page || is_huge_zero_page(page))
> >  		return;
> 
> This really seems like a bit of a hack.  A normal (small) zero page
> won't make it to this point because of the vm_normal_page() check in
> smaps_pte_entry() which hits the _PAGE_SPECIAL bit in the pte.
> 
> Is there a reason we can't set _PAGE_SPECIAL on the huge_zero_page ptes?
>  If we did that, we wouldn't need a special case here.
> 
> If we can't do that for some reason, can we at least teach
> vm_normal_page() about the huge_zero_page in some other way?
> 
Thanks a lot for the comments. I will check whether could remove the
hack.

> >  	if (PageAnon(page))
> > @@ -516,7 +516,8 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
> >  	if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
> >  		smaps_pte_entry(*(pte_t *)pmd, addr, HPAGE_PMD_SIZE, walk);
> >  		spin_unlock(ptl);
> > -		mss->anonymous_thp += HPAGE_PMD_SIZE;
> > +		if (!is_huge_zero_pmd(*pmd))
> > +			mss->anonymous_thp += HPAGE_PMD_SIZE;
> >  		return 0;
> >  	}
> 
> How about we just move this hunk in to smaps_pte_entry()?  Something
> along these lines:
> 
> ...
>         if (PageAnon(page)) {
>                 mss->anonymous += ptent_size;
> +		if (PageTransHuge(page))
> +			mss->anonymous_thp += ptent_size;
> 	}
> 
> If we do that, plus teaching vm_normal_page() about huge_zero_pages, it
> will help keep the hacks and the extra code due to huge pages to a miniumum.
> 
> > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> > index 63579cb..758f569 100644
> > --- a/include/linux/huge_mm.h
> > +++ b/include/linux/huge_mm.h
> > @@ -34,6 +34,10 @@ extern int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
> >  			unsigned long addr, pgprot_t newprot,
> >  			int prot_numa);
> >  
> > +extern bool is_huge_zero_page(struct page *page);
> > +
> > +extern bool is_huge_zero_pmd(pmd_t pmd);
> > +
> >  enum transparent_hugepage_flag {
> >  	TRANSPARENT_HUGEPAGE_FLAG,
> >  	TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index d9a21d06..bedc3ae 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -173,12 +173,12 @@ static int start_khugepaged(void)
> >  static atomic_t huge_zero_refcount;
> >  static struct page *huge_zero_page __read_mostly;
> >  
> > -static inline bool is_huge_zero_page(struct page *page)
> > +bool is_huge_zero_page(struct page *page)
> >  {
> >  	return ACCESS_ONCE(huge_zero_page) == page;
> >  }
> >  
> > -static inline bool is_huge_zero_pmd(pmd_t pmd)
> > +bool is_huge_zero_pmd(pmd_t pmd)
> >  {
> >  	return is_huge_zero_page(pmd_page(pmd));
> >  }
> 
> ^^^ And all these exports.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] smaps should deal with huge zero page exactly same as normal zero page

[Fengwei Yin]

[-- Attachment #1: Type: text/plain, Size: 3596 bytes --]

On Thu, Oct 09, 2014 at 09:36:30AM -0700, Dave Hansen wrote:
> On 10/09/2014 02:19 AM, Fengwei Yin wrote:
> > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > index 80ca4fb..8550b27 100644
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -476,7 +476,7 @@ static void smaps_pte_entry(pte_t ptent, unsigned long addr,
> >  			mss->nonlinear += ptent_size;
> >  	}
> >  
> > -	if (!page)
> > +	if (!page || is_huge_zero_page(page))
> >  		return;
> 
> This really seems like a bit of a hack.  A normal (small) zero page
> won't make it to this point because of the vm_normal_page() check in
> smaps_pte_entry() which hits the _PAGE_SPECIAL bit in the pte.
> 
> Is there a reason we can't set _PAGE_SPECIAL on the huge_zero_page ptes?
>  If we did that, we wouldn't need a special case here.
> 
> If we can't do that for some reason, can we at least teach
> vm_normal_page() about the huge_zero_page in some other way?
I suppose _PAGE_SPECIAL can't work. Two reasons:
1. Not all arch have HAVE_PTE_SPECIAL set. So always need another way to
   handle the arch which has no PTE_SPECIAL.
2. _PAGE_SPECIAL is just for PTE now. If want to add it for huge page,
   we need to introduce pmd_mkspecial() thing which I don't think it's
   worth to do now (unless you want it. :)).

Yes. We could move the check to vm_normal_page(). But it still needs
export functions from huge_memory.c.

Please check the new patch.

> 
> >  	if (PageAnon(page))
> > @@ -516,7 +516,8 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
> >  	if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
> >  		smaps_pte_entry(*(pte_t *)pmd, addr, HPAGE_PMD_SIZE, walk);
> >  		spin_unlock(ptl);
> > -		mss->anonymous_thp += HPAGE_PMD_SIZE;
> > +		if (!is_huge_zero_pmd(*pmd))
> > +			mss->anonymous_thp += HPAGE_PMD_SIZE;
> >  		return 0;
> >  	}
> 
> How about we just move this hunk in to smaps_pte_entry()?  Something
> along these lines:
> 
> ...
>         if (PageAnon(page)) {
>                 mss->anonymous += ptent_size;
> +		if (PageTransHuge(page))
> +			mss->anonymous_thp += ptent_size;
> 	}
Done.
> 
> If we do that, plus teaching vm_normal_page() about huge_zero_pages, it
> will help keep the hacks and the extra code due to huge pages to a miniumum.
> 
> > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> > index 63579cb..758f569 100644
> > --- a/include/linux/huge_mm.h
> > +++ b/include/linux/huge_mm.h
> > @@ -34,6 +34,10 @@ extern int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
> >  			unsigned long addr, pgprot_t newprot,
> >  			int prot_numa);
> >  
> > +extern bool is_huge_zero_page(struct page *page);
> > +
> > +extern bool is_huge_zero_pmd(pmd_t pmd);
> > +
> >  enum transparent_hugepage_flag {
> >  	TRANSPARENT_HUGEPAGE_FLAG,
> >  	TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index d9a21d06..bedc3ae 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -173,12 +173,12 @@ static int start_khugepaged(void)
> >  static atomic_t huge_zero_refcount;
> >  static struct page *huge_zero_page __read_mostly;
> >  
> > -static inline bool is_huge_zero_page(struct page *page)
> > +bool is_huge_zero_page(struct page *page)
> >  {
> >  	return ACCESS_ONCE(huge_zero_page) == page;
> >  }
> >  
> > -static inline bool is_huge_zero_pmd(pmd_t pmd)
> > +bool is_huge_zero_pmd(pmd_t pmd)
> >  {
> >  	return is_huge_zero_page(pmd_page(pmd));
> >  }
> 
> ^^^ And all these exports.

A new function is_huge_zero_pfn() is added to mm/huge_memory.c
and exported.

Thanks.

[-- Attachment #2: 0001-smaps-should-deal-with-huge-zero-page-exactly-same-a.patch --]
[-- Type: text/x-diff, Size: 0 bytes --]

Re: [PATCH] smaps should deal with huge zero page exactly same as normal zero page

[Dave Hansen]

On 10/10/2014 06:21 AM, Fengwei Yin wrote:
> @@ -787,6 +788,9 @@ check_pfn:
>  		return NULL;
>  	}
>  
> +	if (is_huge_zero_pfn(pfn))
> +		return NULL;
> +

That looks a lot better.  One thing, why not put the is_huge_zero_pfn()
check next to the is_zero_pfn() check?

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] smaps should deal with huge zero page exactly same as normal zero page

[Fengwei Yin]

On Fri, Oct 10, 2014 at 07:35:15AM -0700, Dave Hansen wrote:
> On 10/10/2014 06:21 AM, Fengwei Yin wrote:
> > @@ -787,6 +788,9 @@ check_pfn:
> >  		return NULL;
> >  	}
> >  
> > +	if (is_huge_zero_pfn(pfn))
> > +		return NULL;
> > +
> 
> That looks a lot better.  One thing, why not put the is_huge_zero_pfn()
> check next to the is_zero_pfn() check?

On the arch which has PTE_SPECIAL feaure, we need to make sure the
is_huge_zero_pfn() is called after the pfn is checked if !pte_special().

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] smaps should deal with huge zero page exactly same as normal zero page

[Kirill A. Shutemov]

On Fri, Oct 10, 2014 at 09:21:08PM +0800, Fengwei Yin wrote:
> On Thu, Oct 09, 2014 at 09:36:30AM -0700, Dave Hansen wrote:
> > On 10/09/2014 02:19 AM, Fengwei Yin wrote:
> > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > > index 80ca4fb..8550b27 100644
> > > --- a/fs/proc/task_mmu.c
> > > +++ b/fs/proc/task_mmu.c
> > > @@ -476,7 +476,7 @@ static void smaps_pte_entry(pte_t ptent, unsigned long addr,
> > >  			mss->nonlinear += ptent_size;
> > >  	}
> > >  
> > > -	if (!page)
> > > +	if (!page || is_huge_zero_page(page))
> > >  		return;
> > 
> > This really seems like a bit of a hack.  A normal (small) zero page
> > won't make it to this point because of the vm_normal_page() check in
> > smaps_pte_entry() which hits the _PAGE_SPECIAL bit in the pte.
> > 
> > Is there a reason we can't set _PAGE_SPECIAL on the huge_zero_page ptes?
> >  If we did that, we wouldn't need a special case here.
> > 
> > If we can't do that for some reason, can we at least teach
> > vm_normal_page() about the huge_zero_page in some other way?
> I suppose _PAGE_SPECIAL can't work. Two reasons:
> 1. Not all arch have HAVE_PTE_SPECIAL set. So always need another way to
>    handle the arch which has no PTE_SPECIAL.
> 2. _PAGE_SPECIAL is just for PTE now. If want to add it for huge page,
>    we need to introduce pmd_mkspecial() thing which I don't think it's
>    worth to do now (unless you want it. :)).
> 
> Yes. We could move the check to vm_normal_page(). But it still needs
> export functions from huge_memory.c.
> 
> Please check the new patch.
> 
> > 
> > >  	if (PageAnon(page))
> > > @@ -516,7 +516,8 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
> > >  	if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
> > >  		smaps_pte_entry(*(pte_t *)pmd, addr, HPAGE_PMD_SIZE, walk);
> > >  		spin_unlock(ptl);
> > > -		mss->anonymous_thp += HPAGE_PMD_SIZE;
> > > +		if (!is_huge_zero_pmd(*pmd))
> > > +			mss->anonymous_thp += HPAGE_PMD_SIZE;
> > >  		return 0;
> > >  	}
> > 
> > How about we just move this hunk in to smaps_pte_entry()?  Something
> > along these lines:
> > 
> > ...
> >         if (PageAnon(page)) {
> >                 mss->anonymous += ptent_size;
> > +		if (PageTransHuge(page))
> > +			mss->anonymous_thp += ptent_size;
> > 	}
> Done.
> > 
> > If we do that, plus teaching vm_normal_page() about huge_zero_pages, it
> > will help keep the hacks and the extra code due to huge pages to a miniumum.
> > 
> > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> > > index 63579cb..758f569 100644
> > > --- a/include/linux/huge_mm.h
> > > +++ b/include/linux/huge_mm.h
> > > @@ -34,6 +34,10 @@ extern int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
> > >  			unsigned long addr, pgprot_t newprot,
> > >  			int prot_numa);
> > >  
> > > +extern bool is_huge_zero_page(struct page *page);
> > > +
> > > +extern bool is_huge_zero_pmd(pmd_t pmd);
> > > +
> > >  enum transparent_hugepage_flag {
> > >  	TRANSPARENT_HUGEPAGE_FLAG,
> > >  	TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
> > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > > index d9a21d06..bedc3ae 100644
> > > --- a/mm/huge_memory.c
> > > +++ b/mm/huge_memory.c
> > > @@ -173,12 +173,12 @@ static int start_khugepaged(void)
> > >  static atomic_t huge_zero_refcount;
> > >  static struct page *huge_zero_page __read_mostly;
> > >  
> > > -static inline bool is_huge_zero_page(struct page *page)
> > > +bool is_huge_zero_page(struct page *page)
> > >  {
> > >  	return ACCESS_ONCE(huge_zero_page) == page;
> > >  }
> > >  
> > > -static inline bool is_huge_zero_pmd(pmd_t pmd)
> > > +bool is_huge_zero_pmd(pmd_t pmd)
> > >  {
> > >  	return is_huge_zero_page(pmd_page(pmd));
> > >  }
> > 
> > ^^^ And all these exports.
> 
> A new function is_huge_zero_pfn() is added to mm/huge_memory.c
> and exported.
> 
> Thanks.

> From 4e7bdd5bc22874175982ab50303eab32843c753c Mon Sep 17 00:00:00 2001
> From: Fengwei Yin <yfw.kernel@gmail.com>
> Date: Thu, 9 Oct 2014 22:20:58 +0800
> Subject: [PATCH] smaps should deal with huge zero page exactly same as normal
>  zero page.
> 

Description?

> Signed-off-by: Fengwei Yin <yfw.kernel@gmail.com>
> ---
>  fs/proc/task_mmu.c      | 6 ++++--
>  include/linux/huge_mm.h | 2 ++
>  mm/huge_memory.c        | 5 +++++
>  mm/memory.c             | 4 ++++
>  4 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index c341568..fb19c0c 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -471,8 +471,11 @@ static void smaps_pte_entry(pte_t ptent, unsigned long addr,
>  	if (!page)
>  		return;
>  
> -	if (PageAnon(page))
> +	if (PageAnon(page)) {
>  		mss->anonymous += ptent_size;
> +		if (PageTransHuge(page))
> +			mss->anonymous_thp += HPAGE_PMD_SIZE;
> +	}
>  
>  	if (page->index != pgoff)
>  		mss->nonlinear += ptent_size;
> @@ -508,7 +511,6 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
>  	if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
>  		smaps_pte_entry(*(pte_t *)pmd, addr, HPAGE_PMD_SIZE, walk);
>  		spin_unlock(ptl);
> -		mss->anonymous_thp += HPAGE_PMD_SIZE;
>  		return 0;
>  	}
>  
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 63579cb..9bf6263 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -34,6 +34,8 @@ extern int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
>  			unsigned long addr, pgprot_t newprot,
>  			int prot_numa);
>  
> +extern bool is_huge_zero_pfn(unsigned long pfn);
> +
>  enum transparent_hugepage_flag {
>  	TRANSPARENT_HUGEPAGE_FLAG,
>  	TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index f8ffd94..71ca4ed 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -183,6 +183,11 @@ static inline bool is_huge_zero_pmd(pmd_t pmd)
>  	return is_huge_zero_page(pmd_page(pmd));
>  }
>  
> +inline bool is_huge_zero_pfn(unsigned long pfn)

There's no way the function can be inlined.

Otherwise looks good to me.

-- 
 Kirill A. Shutemov

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] smaps should deal with huge zero page exactly same as normal zero page

[Fengwei Yin]

[-- Attachment #1: Type: text/plain, Size: 6548 bytes --]

On Tue, Oct 14, 2014 at 02:57:30PM +0300, Kirill A. Shutemov wrote:
> On Fri, Oct 10, 2014 at 09:21:08PM +0800, Fengwei Yin wrote:
> > On Thu, Oct 09, 2014 at 09:36:30AM -0700, Dave Hansen wrote:
> > > On 10/09/2014 02:19 AM, Fengwei Yin wrote:
> > > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > > > index 80ca4fb..8550b27 100644
> > > > --- a/fs/proc/task_mmu.c
> > > > +++ b/fs/proc/task_mmu.c
> > > > @@ -476,7 +476,7 @@ static void smaps_pte_entry(pte_t ptent, unsigned long addr,
> > > >  			mss->nonlinear += ptent_size;
> > > >  	}
> > > >  
> > > > -	if (!page)
> > > > +	if (!page || is_huge_zero_page(page))
> > > >  		return;
> > > 
> > > This really seems like a bit of a hack.  A normal (small) zero page
> > > won't make it to this point because of the vm_normal_page() check in
> > > smaps_pte_entry() which hits the _PAGE_SPECIAL bit in the pte.
> > > 
> > > Is there a reason we can't set _PAGE_SPECIAL on the huge_zero_page ptes?
> > >  If we did that, we wouldn't need a special case here.
> > > 
> > > If we can't do that for some reason, can we at least teach
> > > vm_normal_page() about the huge_zero_page in some other way?
> > I suppose _PAGE_SPECIAL can't work. Two reasons:
> > 1. Not all arch have HAVE_PTE_SPECIAL set. So always need another way to
> >    handle the arch which has no PTE_SPECIAL.
> > 2. _PAGE_SPECIAL is just for PTE now. If want to add it for huge page,
> >    we need to introduce pmd_mkspecial() thing which I don't think it's
> >    worth to do now (unless you want it. :)).
> > 
> > Yes. We could move the check to vm_normal_page(). But it still needs
> > export functions from huge_memory.c.
> > 
> > Please check the new patch.
> > 
> > > 
> > > >  	if (PageAnon(page))
> > > > @@ -516,7 +516,8 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
> > > >  	if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
> > > >  		smaps_pte_entry(*(pte_t *)pmd, addr, HPAGE_PMD_SIZE, walk);
> > > >  		spin_unlock(ptl);
> > > > -		mss->anonymous_thp += HPAGE_PMD_SIZE;
> > > > +		if (!is_huge_zero_pmd(*pmd))
> > > > +			mss->anonymous_thp += HPAGE_PMD_SIZE;
> > > >  		return 0;
> > > >  	}
> > > 
> > > How about we just move this hunk in to smaps_pte_entry()?  Something
> > > along these lines:
> > > 
> > > ...
> > >         if (PageAnon(page)) {
> > >                 mss->anonymous += ptent_size;
> > > +		if (PageTransHuge(page))
> > > +			mss->anonymous_thp += ptent_size;
> > > 	}
> > Done.
> > > 
> > > If we do that, plus teaching vm_normal_page() about huge_zero_pages, it
> > > will help keep the hacks and the extra code due to huge pages to a miniumum.
> > > 
> > > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> > > > index 63579cb..758f569 100644
> > > > --- a/include/linux/huge_mm.h
> > > > +++ b/include/linux/huge_mm.h
> > > > @@ -34,6 +34,10 @@ extern int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
> > > >  			unsigned long addr, pgprot_t newprot,
> > > >  			int prot_numa);
> > > >  
> > > > +extern bool is_huge_zero_page(struct page *page);
> > > > +
> > > > +extern bool is_huge_zero_pmd(pmd_t pmd);
> > > > +
> > > >  enum transparent_hugepage_flag {
> > > >  	TRANSPARENT_HUGEPAGE_FLAG,
> > > >  	TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
> > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > > > index d9a21d06..bedc3ae 100644
> > > > --- a/mm/huge_memory.c
> > > > +++ b/mm/huge_memory.c
> > > > @@ -173,12 +173,12 @@ static int start_khugepaged(void)
> > > >  static atomic_t huge_zero_refcount;
> > > >  static struct page *huge_zero_page __read_mostly;
> > > >  
> > > > -static inline bool is_huge_zero_page(struct page *page)
> > > > +bool is_huge_zero_page(struct page *page)
> > > >  {
> > > >  	return ACCESS_ONCE(huge_zero_page) == page;
> > > >  }
> > > >  
> > > > -static inline bool is_huge_zero_pmd(pmd_t pmd)
> > > > +bool is_huge_zero_pmd(pmd_t pmd)
> > > >  {
> > > >  	return is_huge_zero_page(pmd_page(pmd));
> > > >  }
> > > 
> > > ^^^ And all these exports.
> > 
> > A new function is_huge_zero_pfn() is added to mm/huge_memory.c
> > and exported.
> > 
> > Thanks.
> 
> > From 4e7bdd5bc22874175982ab50303eab32843c753c Mon Sep 17 00:00:00 2001
> > From: Fengwei Yin <yfw.kernel@gmail.com>
> > Date: Thu, 9 Oct 2014 22:20:58 +0800
> > Subject: [PATCH] smaps should deal with huge zero page exactly same as normal
> >  zero page.
> > 
> 
> Description?
> 
> > Signed-off-by: Fengwei Yin <yfw.kernel@gmail.com>
> > ---
> >  fs/proc/task_mmu.c      | 6 ++++--
> >  include/linux/huge_mm.h | 2 ++
> >  mm/huge_memory.c        | 5 +++++
> >  mm/memory.c             | 4 ++++
> >  4 files changed, 15 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > index c341568..fb19c0c 100644
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -471,8 +471,11 @@ static void smaps_pte_entry(pte_t ptent, unsigned long addr,
> >  	if (!page)
> >  		return;
> >  
> > -	if (PageAnon(page))
> > +	if (PageAnon(page)) {
> >  		mss->anonymous += ptent_size;
> > +		if (PageTransHuge(page))
> > +			mss->anonymous_thp += HPAGE_PMD_SIZE;
> > +	}
> >  
> >  	if (page->index != pgoff)
> >  		mss->nonlinear += ptent_size;
> > @@ -508,7 +511,6 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
> >  	if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
> >  		smaps_pte_entry(*(pte_t *)pmd, addr, HPAGE_PMD_SIZE, walk);
> >  		spin_unlock(ptl);
> > -		mss->anonymous_thp += HPAGE_PMD_SIZE;
> >  		return 0;
> >  	}
> >  
> > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> > index 63579cb..9bf6263 100644
> > --- a/include/linux/huge_mm.h
> > +++ b/include/linux/huge_mm.h
> > @@ -34,6 +34,8 @@ extern int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
> >  			unsigned long addr, pgprot_t newprot,
> >  			int prot_numa);
> >  
> > +extern bool is_huge_zero_pfn(unsigned long pfn);
> > +
> >  enum transparent_hugepage_flag {
> >  	TRANSPARENT_HUGEPAGE_FLAG,
> >  	TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index f8ffd94..71ca4ed 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -183,6 +183,11 @@ static inline bool is_huge_zero_pmd(pmd_t pmd)
> >  	return is_huge_zero_page(pmd_page(pmd));
> >  }
> >  
> > +inline bool is_huge_zero_pfn(unsigned long pfn)
> 
> There's no way the function can be inlined.
> 
> Otherwise looks good to me.
> 
Thanks a lot for the comments. Updated patch attached.
> -- 
>  Kirill A. Shutemov

[-- Attachment #2: 0001-smaps-should-deal-with-huge-zero-page-exactly-same-a.patch --]
[-- Type: text/x-diff, Size: 0 bytes --]

Re: [PATCH] smaps should deal with huge zero page exactly same as normal zero page

[Fengwei Yin]

On Fri, Oct 10, 2014 at 07:35:15AM -0700, Dave Hansen wrote:
> On 10/10/2014 06:21 AM, Fengwei Yin wrote:
> > @@ -787,6 +788,9 @@ check_pfn:
> >  		return NULL;
> >  	}
> >  
> > +	if (is_huge_zero_pfn(pfn))
> > +		return NULL;
> > +
> 
> That looks a lot better.  One thing, why not put the is_huge_zero_pfn()
> check next to the is_zero_pfn() check?
Hi,
If no further comment, what's the next step to push this patch merged?
:). Thanks a lot.

Regards
Yin, Fengwei

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>