On Mon, Oct 27, 2014 at 03:17:48PM -0700, Andrew Morton wrote:
> On Mon, 27 Oct 2014 23:02:13 +0800 Fengwei Yin <yfw.kernel@xxxxxxxxx> wrote:
>
> > We could see following memory info in /proc/xxxx/smaps with THP enabled.
> > 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
> > which is wrong becuase just huge_zero_page/normal_zero_page is used for
> > /dev/zero. Most of the value should be 0.
> >
> > This patch detects huge_zero_page (original implementation just detect
> > normal_zero_page) and avoids to update the wrong value for huge_zero_page.
> >
> > ...
> >
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -41,6 +41,7 @@
> > #include <linux/kernel_stat.h>
> > #include <linux/mm.h>
> > #include <linux/hugetlb.h>
> > +#include <linux/huge_mm.h>
> > #include <linux/mman.h>
> > #include <linux/swap.h>
> > #include <linux/highmem.h>
> > @@ -787,6 +788,9 @@ check_pfn:
> > return NULL;
> > }
> >
> > + if (is_huge_zero_pfn(pfn))
> > + return NULL;
> > +
>
> Why this change?
>
> What effect does it have upon vm_normal_page()'s many existing callers?
Subject: [PATCH v3] smaps should deal with huge zero page exactly same as
normal zero page.
We could see following memory info in /proc/xxxx/smaps with THP enabled.
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
which is wrong becuase just huge_zero_page/normal_zero_page is used for
/dev/zero. Most of the value should be 0.
This patch detects huge_zero_page (original implementation just detect
normal_zero_page) and avoids to update the wrong value for huge_zero_page.
Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Signed-off-by: Fengwei Yin <yfw.kernel@xxxxxxxxx>
---
Hi Andrew,
Please try this patch.
It passed build with/without CONFIG_TRANSPARENT_HUGEPAGE. Thanks.
Regards
Yin, Fengwei
fs/proc/task_mmu.c | 6 ++++--
include/linux/huge_mm.h | 7 +++++++
mm/huge_memory.c | 5 +++++
mm/memory.c | 4 ++++
4 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 4e0388c..735b389 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -474,8 +474,11 @@ 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;
@@ -511,7 +514,6 @@ 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 ad9051b..b594c53 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -157,6 +157,8 @@ static inline int hpage_nr_pages(struct page *page)
extern int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long addr, pmd_t pmd, pmd_t *pmdp);
+extern bool is_huge_zero_pfn(unsigned long pfn);
+
#else /* CONFIG_TRANSPARENT_HUGEPAGE */
#define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
#define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; })
@@ -206,6 +208,11 @@ static inline int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_str
return 0;
}
+static inline bool is_huge_zero_pfn(unsigned long pfn)
+{
+ return 0;
+}
+
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
#endif /* _LINUX_HUGE_MM_H */
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 74c78aa..7e7880c 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));
}
+bool is_huge_zero_pfn(unsigned long pfn)
+{
+ return is_huge_zero_page(pfn_to_page(pfn));
+}
+
static struct page *get_huge_zero_page(void)
{
struct page *zero_page;
diff --git a/mm/memory.c b/mm/memory.c
index 1cc6bfb..eebb6c5 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -41,6 +41,7 @@
#include <linux/kernel_stat.h>
#include <linux/mm.h>
#include <linux/hugetlb.h>
+#include <linux/huge_mm.h>
#include <linux/mman.h>
#include <linux/swap.h>
#include <linux/highmem.h>
@@ -787,6 +788,9 @@ check_pfn:
return NULL;
}
+ if (is_huge_zero_pfn(pfn))
+ return NULL;
+
/*
* NOTE! We still have PageReserved() pages in the page tables.
* eg. VDSO mappings can cause them to exist.
--
2.1.0
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