[PATCH 0/2] Report the size of pages backing VMAs in /proc V3

[PATCH 0/2] Report the size of pages backing VMAs in /proc V3

[Mel Gorman]

The following two patches add support for printing the size of pages used by
the kernel and the MMU to back VMAs. This can be used by a user to verify
that a hugepage-aware application is using the expected page sizes.

The first patch prints the size of page used by the kernel when allocating
pages for a VMA in /proc/pid/smaps. The second patch reports on
the size of page used by the MMU as it can differ - for example on POWER
using 64K as a base pagesize on older processors.

Changelog since V2
  o Drop changes to /proc/pid/maps - could not get agreement and it affects
    procps. Patch to procps was posted but fell into silence. Dropping
    patch as smaps gives the necessary information, just with a bit more
    legwork by the user
  o Drop redundant VM_BUG_ON (Alexey)

Changelog since V1
  o Fix build failure on !CONFIG_HUGETLB_PAGE
  o Uninline helper functions
  o Distinguish between base pagesize and MMU pagesize

 arch/powerpc/include/asm/hugetlb.h |    6 ++++++
 arch/powerpc/mm/hugetlbpage.c      |    7 +++++++
 fs/proc/task_mmu.c                 |    8 ++++++--
 include/linux/hugetlb.h            |    6 ++++++
 mm/hugetlb.c                       |   29 +++++++++++++++++++++++++++++
 5 files changed, 54 insertions(+), 2 deletions(-)

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[PATCH 1/2] Subject: [PATCH] Report the pagesize backing a VMA in /proc/pid/smaps

[Mel Gorman]

It is useful to verify a hugepage-aware application is using the expected
pagesizes for its memory regions. This patch creates an entry called
KernelPageSize in /proc/pid/smaps that is the size of page used by the
kernel to back a VMA. The entry is not called PageSize as it is possible
the MMU uses a different size. This extension should not break any sensible
parser that skips lines containing unrecognised information.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
---
 fs/proc/task_mmu.c      |    6 ++++--
 include/linux/hugetlb.h |    3 +++
 mm/hugetlb.c            |   16 ++++++++++++++++
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 4806830..71c9868 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -391,7 +391,8 @@ static int show_smap(struct seq_file *m, void *v)
 		   "Private_Clean:  %8lu kB\n"
 		   "Private_Dirty:  %8lu kB\n"
 		   "Referenced:     %8lu kB\n"
-		   "Swap:           %8lu kB\n",
+		   "Swap:           %8lu kB\n"
+		   "KernelPageSize: %8lu kB\n",
 		   (vma->vm_end - vma->vm_start) >> 10,
 		   mss.resident >> 10,
 		   (unsigned long)(mss.pss >> (10 + PSS_SHIFT)),
@@ -400,7 +401,8 @@ static int show_smap(struct seq_file *m, void *v)
 		   mss.private_clean >> 10,
 		   mss.private_dirty >> 10,
 		   mss.referenced >> 10,
-		   mss.swap >> 10);
+		   mss.swap >> 10,
+		   vma_kernel_pagesize(vma) >> 10);
 
 	return ret;
 }
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 32e0ef0..ace04a7 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -231,6 +231,8 @@ static inline unsigned long huge_page_size(struct hstate *h)
 	return (unsigned long)PAGE_SIZE << h->order;
 }
 
+extern unsigned long vma_kernel_pagesize(struct vm_area_struct *vma);
+
 static inline unsigned long huge_page_mask(struct hstate *h)
 {
 	return h->mask;
@@ -271,6 +273,7 @@ struct hstate {};
 #define hstate_inode(i) NULL
 #define huge_page_size(h) PAGE_SIZE
 #define huge_page_mask(h) PAGE_MASK
+#define vma_kernel_pagesize(v) PAGE_SIZE
 #define huge_page_order(h) 0
 #define huge_page_shift(h) PAGE_SHIFT
 static inline unsigned int pages_per_huge_page(struct hstate *h)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 67a7119..7cb27ec 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -219,6 +219,22 @@ static pgoff_t vma_hugecache_offset(struct hstate *h,
 }
 
 /*
+ * Return the size of the pages allocated when backing a VMA. In the majority
+ * cases this will be same size as used by the page table entries.
+ */
+unsigned long vma_kernel_pagesize(struct vm_area_struct *vma)
+{
+	struct hstate *hstate;
+
+	if (!is_vm_hugetlb_page(vma))
+		return PAGE_SIZE;
+
+	hstate = hstate_vma(vma);
+
+	return 1UL << (hstate->order + PAGE_SHIFT);
+}
+
+/*
  * Flags for MAP_PRIVATE reservations.  These are stored in the bottom
  * bits of the reservation map pointer, which are always clear due to
  * alignment.
-- 
1.5.6.5

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[PATCH 2/2] Report the MMU pagesize in /proc/pid/smaps

[Mel Gorman]

The KernelPageSize entry in /proc/pid/smaps is the pagesize used by the
kernel to back a VMA. This matches the size used by the MMU in the majority
of cases. However, one counter-example occurs on PPC64 kernels whereby
a kernel using 64K as a base pagesize may still use 4K pages for the MMU
on older processor. To distinguish, this patch reports MMUPageSize as the
pagesize used by the MMU in /proc/pid/smaps.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
---
 arch/powerpc/include/asm/hugetlb.h |    6 ++++++
 arch/powerpc/mm/hugetlbpage.c      |    7 +++++++
 fs/proc/task_mmu.c                 |    6 ++++--
 include/linux/hugetlb.h            |    3 +++
 mm/hugetlb.c                       |   13 +++++++++++++
 5 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/hugetlb.h b/arch/powerpc/include/asm/hugetlb.h
index 26f0d0a..2655146 100644
--- a/arch/powerpc/include/asm/hugetlb.h
+++ b/arch/powerpc/include/asm/hugetlb.h
@@ -18,6 +18,12 @@ pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
 			      pte_t *ptep);
 
 /*
+ * The version of vma_mmu_pagesize() in arch/powerpc/mm/hugetlbpage.c needs
+ * to override the version in mm/hugetlb.c
+ */
+#define vma_mmu_pagesize vma_mmu_pagesize
+
+/*
  * If the arch doesn't supply something else, assume that hugepage
  * size aligned regions are ok without further preparation.
  */
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index a117024..edc0c69 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -510,6 +510,13 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 	return slice_get_unmapped_area(addr, len, flags, mmu_psize, 1, 0);
 }
 
+unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
+{
+	unsigned int psize = get_slice_psize(vma->vm_mm, vma->vm_start);
+
+	return 1UL << mmu_psize_to_shift(psize);
+}
+
 /*
  * Called by asm hashtable.S for doing lazy icache flush
  */
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 71c9868..3517892 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -392,7 +392,8 @@ static int show_smap(struct seq_file *m, void *v)
 		   "Private_Dirty:  %8lu kB\n"
 		   "Referenced:     %8lu kB\n"
 		   "Swap:           %8lu kB\n"
-		   "KernelPageSize: %8lu kB\n",
+		   "KernelPageSize: %8lu kB\n"
+		   "MMUPageSize:    %8lu kB\n",
 		   (vma->vm_end - vma->vm_start) >> 10,
 		   mss.resident >> 10,
 		   (unsigned long)(mss.pss >> (10 + PSS_SHIFT)),
@@ -402,7 +403,8 @@ static int show_smap(struct seq_file *m, void *v)
 		   mss.private_dirty >> 10,
 		   mss.referenced >> 10,
 		   mss.swap >> 10,
-		   vma_kernel_pagesize(vma) >> 10);
+		   vma_kernel_pagesize(vma) >> 10,
+		   vma_mmu_pagesize(vma) >> 10);
 
 	return ret;
 }
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index ace04a7..5056021 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -233,6 +233,8 @@ static inline unsigned long huge_page_size(struct hstate *h)
 
 extern unsigned long vma_kernel_pagesize(struct vm_area_struct *vma);
 
+extern unsigned long vma_mmu_pagesize(struct vm_area_struct *vma);
+
 static inline unsigned long huge_page_mask(struct hstate *h)
 {
 	return h->mask;
@@ -274,6 +276,7 @@ struct hstate {};
 #define huge_page_size(h) PAGE_SIZE
 #define huge_page_mask(h) PAGE_MASK
 #define vma_kernel_pagesize(v) PAGE_SIZE
+#define vma_mmu_pagesize(v) PAGE_SIZE
 #define huge_page_order(h) 0
 #define huge_page_shift(h) PAGE_SHIFT
 static inline unsigned int pages_per_huge_page(struct hstate *h)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7cb27ec..fee3d1d 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -235,6 +235,19 @@ unsigned long vma_kernel_pagesize(struct vm_area_struct *vma)
 }
 
 /*
+ * Return the page size being used by the MMU to back a VMA. In the majority
+ * of cases, the page size used by the kernel matches the MMU size. On
+ * architectures where it differs, an architecture-specific version of this
+ * function is required.
+ */
+#ifndef vma_mmu_pagesize
+unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
+{
+	return vma_kernel_pagesize(vma);
+}
+#endif
+
+/*
  * Flags for MAP_PRIVATE reservations.  These are stored in the bottom
  * bits of the reservation map pointer, which are always clear due to
  * alignment.
-- 
1.5.6.5

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Re: [PATCH 1/2] Subject: [PATCH] Report the pagesize backing a VMA in /proc/pid/smaps

[KOSAKI Motohiro]

Hi

> It is useful to verify a hugepage-aware application is using the expected
> pagesizes for its memory regions. This patch creates an entry called
> KernelPageSize in /proc/pid/smaps that is the size of page used by the
> kernel to back a VMA. The entry is not called PageSize as it is possible
> the MMU uses a different size. This extension should not break any sensible
> parser that skips lines containing unrecognised information.
>
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>

ack.

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[PATCH 0/2] Report the size of pages backing VMAs in /proc V3

[Mel Gorman]

The following two patches add support for printing the size of pages used
by the kernel to back VMAs in maps and smaps. This can be used by a user
to verify that a hugepage-aware application is using the expected page sizes.
In one case the pagesize used by the MMU differs from the size used by the
kernel. This is on PPC64 using 64K as a base page size running on a processor
that does not support 64K in the MMU. In this case, the kernel uses 64K pages
but the MMU is still using 4K.

The first patch prints the size of page used by the kernel when allocating
pages for a VMA in /proc/pid/smaps and should not be considered too
contentious as it is highly unlikely to break any parsers.  The second patch
reports the size of page used by hugetlbfs regions in /proc/pid/maps. There is
a possibility that the final patch will break parsers but they are arguably
already broken. More details are in the patches themselves.

Thanks to KOSAKI Motohiro for rebasing the patches onto mmotm, reviewing
and testing.

Changelog since V2
  o Drop printing of MMUPageSize (mel)
  o Rebase onto mmotm (KOSAKI Motohiro)

Changelog since V1
  o Fix build failure on !CONFIG_HUGETLB_PAGE
  o Uninline helper functions
  o Distinguish between base pagesize and MMU pagesize

 fs/proc/task_mmu.c      |   27 ++++++++++++++++++---------
 include/linux/hugetlb.h |    3 +++
 mm/hugetlb.c            |   17 +++++++++++++++++
 3 files changed, 38 insertions(+), 9 deletions(-)

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