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[PATCH v1 1/3] /proc/kpageflags: return KPF_BUDDY for "tail" buddy pages

Started byNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
First post2016-02-04 08:10 +0100
Last post2016-02-05 00:40 +0100
Articles 3 — 2 participants

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  [PATCH v1 1/3] /proc/kpageflags: return KPF_BUDDY for "tail" buddy pages Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> - 2016-02-04 08:10 +0100
    Re: [PATCH v1 1/3] /proc/kpageflags: return KPF_BUDDY for "tail"  buddy pages Vladimir Davydov <vdavydov@virtuozzo.com> - 2016-02-04 17:50 +0100
      Re: [PATCH v1 1/3] /proc/kpageflags: return KPF_BUDDY for "tail"  buddy pages Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> - 2016-02-05 00:40 +0100

#1326450 — [PATCH v1 1/3] /proc/kpageflags: return KPF_BUDDY for "tail" buddy pages

FromNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Date2016-02-04 08:10 +0100
Subject[PATCH v1 1/3] /proc/kpageflags: return KPF_BUDDY for "tail" buddy pages
Message-ID<qYmdb-5kI-3@gated-at.bofh.it>
Currently /proc/kpageflags returns nothing for "tail" buddy pages, which
is inconvenient when grasping how free pages are distributed. This patch
sets KPF_BUDDY for such pages.

With this patch:

  $ grep MemFree /proc/meminfo ; tools/vm/page-types -b buddy
  MemFree:         3134992 kB
               flags      page-count       MB  symbolic-flags                     long-symbolic-flags
  0x0000000000000400          779272     3044  __________B_______________________________ buddy
  0x0000000000000c00            4385       17  __________BM______________________________ buddy,mmap
               total          783657     3061

783657 pages is 3134628 kB (roughly consistent with the global counter,)
so it's OK.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
---
 fs/proc/page.c             | 2 ++
 include/linux/page-flags.h | 2 ++
 mm/internal.h              | 3 ---
 mm/page_alloc.c            | 2 --
 4 files changed, 4 insertions(+), 5 deletions(-)

diff --git v4.5-rc2-mmotm-2016-02-02-17-08/fs/proc/page.c v4.5-rc2-mmotm-2016-02-02-17-08_patched/fs/proc/page.c
index b2855ee..42998bb 100644
--- v4.5-rc2-mmotm-2016-02-02-17-08/fs/proc/page.c
+++ v4.5-rc2-mmotm-2016-02-02-17-08_patched/fs/proc/page.c
@@ -148,6 +148,8 @@ u64 stable_page_flags(struct page *page)
 	 */
 	if (PageBuddy(page))
 		u |= 1 << KPF_BUDDY;
+	else if (page_count(page) == 0 && is_free_buddy_page(page))
+		u |= 1 << KPF_BUDDY;
 
 	if (PageBalloon(page))
 		u |= 1 << KPF_BALLOON;
diff --git v4.5-rc2-mmotm-2016-02-02-17-08/include/linux/page-flags.h v4.5-rc2-mmotm-2016-02-02-17-08_patched/include/linux/page-flags.h
index 19724e6..5976955 100644
--- v4.5-rc2-mmotm-2016-02-02-17-08/include/linux/page-flags.h
+++ v4.5-rc2-mmotm-2016-02-02-17-08_patched/include/linux/page-flags.h
@@ -593,6 +593,8 @@ static inline void __ClearPageBuddy(struct page *page)
 	atomic_set(&page->_mapcount, -1);
 }
 
+extern bool is_free_buddy_page(struct page *page);
+
 #define PAGE_BALLOON_MAPCOUNT_VALUE (-256)
 
 static inline int PageBalloon(struct page *page)
diff --git v4.5-rc2-mmotm-2016-02-02-17-08/mm/internal.h v4.5-rc2-mmotm-2016-02-02-17-08_patched/mm/internal.h
index 271ad95..06071af 100644
--- v4.5-rc2-mmotm-2016-02-02-17-08/mm/internal.h
+++ v4.5-rc2-mmotm-2016-02-02-17-08_patched/mm/internal.h
@@ -145,9 +145,6 @@ extern int __isolate_free_page(struct page *page, unsigned int order);
 extern void __free_pages_bootmem(struct page *page, unsigned long pfn,
 					unsigned int order);
 extern void prep_compound_page(struct page *page, unsigned int order);
-#ifdef CONFIG_MEMORY_FAILURE
-extern bool is_free_buddy_page(struct page *page);
-#endif
 extern int user_min_free_kbytes;
 
 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
diff --git v4.5-rc2-mmotm-2016-02-02-17-08/mm/page_alloc.c v4.5-rc2-mmotm-2016-02-02-17-08_patched/mm/page_alloc.c
index 555b9d2..d9c8b70 100644
--- v4.5-rc2-mmotm-2016-02-02-17-08/mm/page_alloc.c
+++ v4.5-rc2-mmotm-2016-02-02-17-08_patched/mm/page_alloc.c
@@ -7182,7 +7182,6 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
 }
 #endif
 
-#ifdef CONFIG_MEMORY_FAILURE
 bool is_free_buddy_page(struct page *page)
 {
 	struct zone *zone = page_zone(page);
@@ -7201,4 +7200,3 @@ bool is_free_buddy_page(struct page *page)
 
 	return order < MAX_ORDER;
 }
-#endif
-- 
2.7.0

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#1326997 — Re: [PATCH v1 1/3] /proc/kpageflags: return KPF_BUDDY for "tail" buddy pages

FromVladimir Davydov <vdavydov@virtuozzo.com>
Date2016-02-04 17:50 +0100
SubjectRe: [PATCH v1 1/3] /proc/kpageflags: return KPF_BUDDY for "tail" buddy pages
Message-ID<qYvgu-4wj-17@gated-at.bofh.it>
In reply to#1326450
On Thu, Feb 04, 2016 at 04:08:01PM +0900, Naoya Horiguchi wrote:
> Currently /proc/kpageflags returns nothing for "tail" buddy pages, which
> is inconvenient when grasping how free pages are distributed. This patch
> sets KPF_BUDDY for such pages.

Looks reasonable to me,

Reviewed-by: Vladimir Davydov <vdavydov@virtuozzo.com>

> 
> With this patch:
> 
>   $ grep MemFree /proc/meminfo ; tools/vm/page-types -b buddy
>   MemFree:         3134992 kB
>                flags      page-count       MB  symbolic-flags                     long-symbolic-flags
>   0x0000000000000400          779272     3044  __________B_______________________________ buddy
>   0x0000000000000c00            4385       17  __________BM______________________________ buddy,mmap
>                total          783657     3061

Why are buddy pages reported as mmapped? That looks weird. Shouldn't we
fix it? Something like this, may be?
--
From: Vladimir Davydov <vdavydov@virtuozzo.com>
Subject: [PATCH] proc: kpageflags: do not report buddy and balloon pages as
 mapped

PageBuddy and PageBalloon are not usual page flags - they are identified
by a special negative (so as not to confuse with mapped pages) value of
page->_mapcount. Since /proc/kpageflags uses page_mapcount helper to
check if a page is mapped, it reports pages of these kinds as being
mapped, which is confusing. Fix that by replacing page_mapcount with
page_mapped.

Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>

diff --git a/fs/proc/page.c b/fs/proc/page.c
index b2855eea5405..332450d87ea4 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -105,7 +105,7 @@ u64 stable_page_flags(struct page *page)
 	 * Note that page->_mapcount is overloaded in SLOB/SLUB/SLQB, so the
 	 * simple test in page_mapcount() is not enough.
 	 */
-	if (!PageSlab(page) && page_mapcount(page))
+	if (!PageSlab(page) && page_mapped(page))
 		u |= 1 << KPF_MMAP;
 	if (PageAnon(page))
 		u |= 1 << KPF_ANON;

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#1327350 — Re: [PATCH v1 1/3] /proc/kpageflags: return KPF_BUDDY for "tail" buddy pages

FromNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Date2016-02-05 00:40 +0100
SubjectRe: [PATCH v1 1/3] /proc/kpageflags: return KPF_BUDDY for "tail" buddy pages
Message-ID<qYBFg-u5-13@gated-at.bofh.it>
In reply to#1326997
On Thu, Feb 04, 2016 at 07:42:26PM +0300, Vladimir Davydov wrote:
> On Thu, Feb 04, 2016 at 04:08:01PM +0900, Naoya Horiguchi wrote:
> > Currently /proc/kpageflags returns nothing for "tail" buddy pages, which
> > is inconvenient when grasping how free pages are distributed. This patch
> > sets KPF_BUDDY for such pages.
> 
> Looks reasonable to me,
> 
> Reviewed-by: Vladimir Davydov <vdavydov@virtuozzo.com>

Thank you.

> > 
> > With this patch:
> > 
> >   $ grep MemFree /proc/meminfo ; tools/vm/page-types -b buddy
> >   MemFree:         3134992 kB
> >                flags      page-count       MB  symbolic-flags                     long-symbolic-flags
> >   0x0000000000000400          779272     3044  __________B_______________________________ buddy
> >   0x0000000000000c00            4385       17  __________BM______________________________ buddy,mmap
> >                total          783657     3061
> 
> Why are buddy pages reported as mmapped? That looks weird. Shouldn't we
> fix it? Something like this, may be?
> 
> --
> From: Vladimir Davydov <vdavydov@virtuozzo.com>
> Subject: [PATCH] proc: kpageflags: do not report buddy and balloon pages as
>  mapped
> 
> PageBuddy and PageBalloon are not usual page flags - they are identified
> by a special negative (so as not to confuse with mapped pages) value of
> page->_mapcount. Since /proc/kpageflags uses page_mapcount helper to
> check if a page is mapped, it reports pages of these kinds as being
> mapped, which is confusing. Fix that by replacing page_mapcount with
> page_mapped.
> 
> Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
> 
> diff --git a/fs/proc/page.c b/fs/proc/page.c
> index b2855eea5405..332450d87ea4 100644
> --- a/fs/proc/page.c
> +++ b/fs/proc/page.c
> @@ -105,7 +105,7 @@ u64 stable_page_flags(struct page *page)
>  	 * Note that page->_mapcount is overloaded in SLOB/SLUB/SLQB, so the
>  	 * simple test in page_mapcount() is not enough.

We can do s/page_mapcount/page_mapped/ for this line too.

>  	 */
> -	if (!PageSlab(page) && page_mapcount(page))
> +	if (!PageSlab(page) && page_mapped(page))

Look good to me.

Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

>  		u |= 1 << KPF_MMAP;
>  	if (PageAnon(page))
>  		u |= 1 << KPF_ANON;

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