[PATCH v10 00/10] complete deferred page initialization

[PATCH v10 00/10] complete deferred page initialization

[Pavel Tatashin]

Changelog:
v10 - v9
- Addressed new comments from Michal Hocko.
- Sent "mm: deferred_init_memmap improvements" as a separate patch as
  it is also fixing existing problem.
- Merged "mm: stop zeroing memory during allocation in vmemmap" with
  "mm: zero struct pages during initialization".
- Added more comments "mm: zero reserved and unavailable struct pages"

v9 - v8
- Addressed comments raised by Mark Rutland and Ard Biesheuvel: changed
  kasan implementation. Added a new function: kasan_map_populate() that
  zeroes the allocated and mapped memory

v8 - v7
- Added Acked-by's from Dave Miller for SPARC changes
- Fixed a minor compiling issue on tile architecture reported by kbuild

v7 - v6
- Addressed comments from Michal Hocko
- memblock_discard() patch was removed from this series and integrated
  separately
- Fixed bug reported by kbuild test robot new patch:
  mm: zero reserved and unavailable struct pages
- Removed patch
  x86/mm: reserve only exiting low pages
  As, it is not needed anymore, because of the previous fix 
- Re-wrote deferred_init_memmap(), found and fixed an existing bug, where
  page variable is not reset when zone holes present.
- Merged several patches together per Michal request
- Added performance data including raw logs

v6 - v5
- Fixed ARM64 + kasan code, as reported by Ard Biesheuvel
- Tested ARM64 code in qemu and found few more issues, that I fixed in this
  iteration
- Added page roundup/rounddown to x86 and arm zeroing routines to zero the
  whole allocated range, instead of only provided address range.
- Addressed SPARC related comment from Sam Ravnborg
- Fixed section mismatch warnings related to memblock_discard().

v5 - v4
- Fixed build issues reported by kbuild on various configurations
v4 - v3
- Rewrote code to zero sturct pages in __init_single_page() as
  suggested by Michal Hocko
- Added code to handle issues related to accessing struct page
  memory before they are initialized.

v3 - v2
- Addressed David Miller comments about one change per patch:
    * Splited changes to platforms into 4 patches
    * Made "do not zero vmemmap_buf" as a separate patch

v2 - v1
- Per request, added s390 to deferred "struct page" zeroing
- Collected performance data on x86 which proofs the importance to
  keep memset() as prefetch (see below).

SMP machines can benefit from the DEFERRED_STRUCT_PAGE_INIT config option,
which defers initializing struct pages until all cpus have been started so
it can be done in parallel.

However, this feature is sub-optimal, because the deferred page
initialization code expects that the struct pages have already been zeroed,
and the zeroing is done early in boot with a single thread only.  Also, we
access that memory and set flags before struct pages are initialized. All
of this is fixed in this patchset.

In this work we do the following:
- Never read access struct page until it was initialized
- Never set any fields in struct pages before they are initialized
- Zero struct page at the beginning of struct page initialization

==========================================================================
Performance improvements on x86 machine with 8 nodes:
Intel(R) Xeon(R) CPU E7-8895 v3 @ 2.60GHz and 1T of memory:
                        TIME          SPEED UP
base no deferred:       95.796233s
fix no deferred:        79.978956s    19.77%

base deferred:          77.254713s
fix deferred:           55.050509s    40.34%
==========================================================================
SPARC M6 3600 MHz with 15T of memory
                        TIME          SPEED UP
base no deferred:       358.335727s
fix no deferred:        302.320936s   18.52%

base deferred:          237.534603s
fix deferred:           182.103003s   30.44%
==========================================================================
Raw dmesg output with timestamps:
x86 base no deferred:    https://hastebin.com/ofunepurit.scala
x86 base deferred:       https://hastebin.com/ifazegeyas.scala
x86 fix no deferred:     https://hastebin.com/pegocohevo.scala
x86 fix deferred:        https://hastebin.com/ofupevikuk.scala
sparc base no deferred:  https://hastebin.com/ibobeteken.go
sparc base deferred:     https://hastebin.com/fariqimiyu.go
sparc fix no deferred:   https://hastebin.com/muhegoheyi.go
sparc fix deferred:      https://hastebin.com/xadinobutu.go

Pavel Tatashin (10):
  x86/mm: setting fields in deferred pages
  sparc64/mm: setting fields in deferred pages
  sparc64: simplify vmemmap_populate
  mm: defining memblock_virt_alloc_try_nid_raw
  mm: zero reserved and unavailable struct pages
  mm/kasan: kasan specific map populate function
  x86/kasan: use kasan_map_populate()
  arm64/kasan: use kasan_map_populate()
  mm: stop zeroing memory during allocation in vmemmap
  sparc64: optimized struct page zeroing

 arch/arm64/include/asm/pgtable.h    |  3 ++
 arch/arm64/mm/kasan_init.c          | 12 +++----
 arch/sparc/include/asm/pgtable_64.h | 30 +++++++++++++++++
 arch/sparc/mm/init_64.c             | 32 ++++++++----------
 arch/x86/mm/init_64.c               | 10 ++++--
 arch/x86/mm/kasan_init_64.c         |  8 ++---
 include/linux/bootmem.h             | 27 +++++++++++++++
 include/linux/kasan.h               |  2 ++
 include/linux/memblock.h            | 16 +++++++++
 include/linux/mm.h                  | 26 ++++++++++++++
 mm/kasan/kasan_init.c               | 67 +++++++++++++++++++++++++++++++++++++
 mm/memblock.c                       | 60 +++++++++++++++++++++++++++++----
 mm/page_alloc.c                     | 54 +++++++++++++++++++++++++-----
 mm/sparse-vmemmap.c                 | 15 ++++-----
 mm/sparse.c                         |  6 ++--
 15 files changed, 312 insertions(+), 56 deletions(-)

-- 
2.14.2

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[PATCH v10 01/10] x86/mm: setting fields in deferred pages

[Pavel Tatashin]

Without deferred struct page feature (CONFIG_DEFERRED_STRUCT_PAGE_INIT),
flags and other fields in "struct page"es are never changed prior to first
initializing struct pages by going through __init_single_page().

With deferred struct page feature enabled, however, we set fields in
register_page_bootmem_info that are subsequently clobbered right after in
free_all_bootmem:

        mem_init() {
                register_page_bootmem_info();
                free_all_bootmem();
                ...
        }

When register_page_bootmem_info() is called only non-deferred struct pages
are initialized. But, this function goes through some reserved pages which
might be part of the deferred, and thus are not yet initialized.

  mem_init
   register_page_bootmem_info
    register_page_bootmem_info_node
     get_page_bootmem
      .. setting fields here ..
      such as: page->freelist = (void *)type;

  free_all_bootmem()
   free_low_memory_core_early()
    for_each_reserved_mem_region()
     reserve_bootmem_region()
      init_reserved_page() <- Only if this is deferred reserved page
       __init_single_pfn()
        __init_single_page()
            memset(0) <-- Loose the set fields here

We end-up with issue where, currently we do not observe problem as memory
is explicitly zeroed. But, if flag asserts are changed we can start hitting
issues.

Also, because in this patch series we will stop zeroing struct page memory
during allocation, we must make sure that struct pages are properly
initialized prior to using them.

The deferred-reserved pages are initialized in free_all_bootmem().
Therefore, the fix is to switch the above calls.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Reviewed-by: Bob Picco <bob.picco@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
---
 arch/x86/mm/init_64.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 5ea1c3c2636e..8822523fdcd7 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1182,12 +1182,18 @@ void __init mem_init(void)
 
 	/* clear_bss() already clear the empty_zero_page */
 
-	register_page_bootmem_info();
-
 	/* this will put all memory onto the freelists */
 	free_all_bootmem();
 	after_bootmem = 1;
 
+	/*
+	 * Must be done after boot memory is put on freelist, because here we
+	 * might set fields in deferred struct pages that have not yet been
+	 * initialized, and free_all_bootmem() initializes all the reserved
+	 * deferred pages for us.
+	 */
+	register_page_bootmem_info();
+
 	/* Register memory areas for /proc/kcore */
 	kclist_add(&kcore_vsyscall, (void *)VSYSCALL_ADDR,
 			 PAGE_SIZE, KCORE_OTHER);
-- 
2.14.2

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[PATCH v10 02/10] sparc64/mm: setting fields in deferred pages

[Pavel Tatashin]

Without deferred struct page feature (CONFIG_DEFERRED_STRUCT_PAGE_INIT),
flags and other fields in "struct page"es are never changed prior to first
initializing struct pages by going through __init_single_page().

With deferred struct page feature enabled there is a case where we set some
fields prior to initializing:

mem_init() {
     register_page_bootmem_info();
     free_all_bootmem();
     ...
}

When register_page_bootmem_info() is called only non-deferred struct pages
are initialized. But, this function goes through some reserved pages which
might be part of the deferred, and thus are not yet initialized.

mem_init
register_page_bootmem_info
register_page_bootmem_info_node
 get_page_bootmem
  .. setting fields here ..
  such as: page->freelist = (void *)type;

free_all_bootmem()
free_low_memory_core_early()
 for_each_reserved_mem_region()
  reserve_bootmem_region()
   init_reserved_page() <- Only if this is deferred reserved page
    __init_single_pfn()
     __init_single_page()
      memset(0) <-- Loose the set fields here

We end-up with similar issue as in the previous patch, where currently we
do not observe problem as memory is zeroed. But, if flag asserts are
changed we can start hitting issues.

Also, because in this patch series we will stop zeroing struct page memory
during allocation, we must make sure that struct pages are properly
initialized prior to using them.

The deferred-reserved pages are initialized in free_all_bootmem().
Therefore, the fix is to switch the above calls.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Reviewed-by: Bob Picco <bob.picco@oracle.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Michal Hocko <mhocko@suse.com>
---
 arch/sparc/mm/init_64.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
index 6034569e2c0d..caed495544e9 100644
--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -2548,9 +2548,16 @@ void __init mem_init(void)
 {
 	high_memory = __va(last_valid_pfn << PAGE_SHIFT);
 
-	register_page_bootmem_info();
 	free_all_bootmem();
 
+	/*
+	 * Must be done after boot memory is put on freelist, because here we
+	 * might set fields in deferred struct pages that have not yet been
+	 * initialized, and free_all_bootmem() initializes all the reserved
+	 * deferred pages for us.
+	 */
+	register_page_bootmem_info();
+
 	/*
 	 * Set up the zero page, mark it reserved, so that page count
 	 * is not manipulated when freeing the page from user ptes.
-- 
2.14.2

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[PATCH v10 03/10] sparc64: simplify vmemmap_populate

[Pavel Tatashin]

Remove duplicating code by using common functions
vmemmap_pud_populate and vmemmap_pgd_populate.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Reviewed-by: Bob Picco <bob.picco@oracle.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Michal Hocko <mhocko@suse.com>
---
 arch/sparc/mm/init_64.c | 23 ++++++-----------------
 1 file changed, 6 insertions(+), 17 deletions(-)

diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
index caed495544e9..6839db3ffe1d 100644
--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -2652,30 +2652,19 @@ int __meminit vmemmap_populate(unsigned long vstart, unsigned long vend,
 	vstart = vstart & PMD_MASK;
 	vend = ALIGN(vend, PMD_SIZE);
 	for (; vstart < vend; vstart += PMD_SIZE) {
-		pgd_t *pgd = pgd_offset_k(vstart);
+		pgd_t *pgd = vmemmap_pgd_populate(vstart, node);
 		unsigned long pte;
 		pud_t *pud;
 		pmd_t *pmd;
 
-		if (pgd_none(*pgd)) {
-			pud_t *new = vmemmap_alloc_block(PAGE_SIZE, node);
+		if (!pgd)
+			return -ENOMEM;
 
-			if (!new)
-				return -ENOMEM;
-			pgd_populate(&init_mm, pgd, new);
-		}
-
-		pud = pud_offset(pgd, vstart);
-		if (pud_none(*pud)) {
-			pmd_t *new = vmemmap_alloc_block(PAGE_SIZE, node);
-
-			if (!new)
-				return -ENOMEM;
-			pud_populate(&init_mm, pud, new);
-		}
+		pud = vmemmap_pud_populate(pgd, vstart, node);
+		if (!pud)
+			return -ENOMEM;
 
 		pmd = pmd_offset(pud, vstart);
-
 		pte = pmd_val(*pmd);
 		if (!(pte & _PAGE_VALID)) {
 			void *block = vmemmap_alloc_block(PMD_SIZE, node);
-- 
2.14.2

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[PATCH v10 04/10] mm: defining memblock_virt_alloc_try_nid_raw

[Pavel Tatashin]

* A new variant of memblock_virt_alloc_* allocations:
memblock_virt_alloc_try_nid_raw()
    - Does not zero the allocated memory
    - Does not panic if request cannot be satisfied

* optimize early system hash allocations

Clients can call alloc_large_system_hash() with flag: HASH_ZERO to specify
that memory that was allocated for system hash needs to be zeroed,
otherwise the memory does not need to be zeroed, and client will initialize
it.

If memory does not need to be zero'd, call the new
memblock_virt_alloc_raw() interface, and thus improve the boot performance.

* debug for raw alloctor

When CONFIG_DEBUG_VM is enabled, this patch sets all the memory that is
returned by memblock_virt_alloc_try_nid_raw() to ones to ensure that no
places excpect zeroed memory.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Reviewed-by: Bob Picco <bob.picco@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
---
 include/linux/bootmem.h | 27 ++++++++++++++++++++++
 mm/memblock.c           | 60 +++++++++++++++++++++++++++++++++++++++++++------
 mm/page_alloc.c         | 15 ++++++-------
 3 files changed, 87 insertions(+), 15 deletions(-)

diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h
index e223d91b6439..ea30b3987282 100644
--- a/include/linux/bootmem.h
+++ b/include/linux/bootmem.h
@@ -160,6 +160,9 @@ extern void *__alloc_bootmem_low_node(pg_data_t *pgdat,
 #define BOOTMEM_ALLOC_ANYWHERE		(~(phys_addr_t)0)
 
 /* FIXME: Move to memblock.h at a point where we remove nobootmem.c */
+void *memblock_virt_alloc_try_nid_raw(phys_addr_t size, phys_addr_t align,
+				      phys_addr_t min_addr,
+				      phys_addr_t max_addr, int nid);
 void *memblock_virt_alloc_try_nid_nopanic(phys_addr_t size,
 		phys_addr_t align, phys_addr_t min_addr,
 		phys_addr_t max_addr, int nid);
@@ -176,6 +179,14 @@ static inline void * __init memblock_virt_alloc(
 					    NUMA_NO_NODE);
 }
 
+static inline void * __init memblock_virt_alloc_raw(
+					phys_addr_t size,  phys_addr_t align)
+{
+	return memblock_virt_alloc_try_nid_raw(size, align, BOOTMEM_LOW_LIMIT,
+					    BOOTMEM_ALLOC_ACCESSIBLE,
+					    NUMA_NO_NODE);
+}
+
 static inline void * __init memblock_virt_alloc_nopanic(
 					phys_addr_t size, phys_addr_t align)
 {
@@ -257,6 +268,14 @@ static inline void * __init memblock_virt_alloc(
 	return __alloc_bootmem(size, align, BOOTMEM_LOW_LIMIT);
 }
 
+static inline void * __init memblock_virt_alloc_raw(
+					phys_addr_t size,  phys_addr_t align)
+{
+	if (!align)
+		align = SMP_CACHE_BYTES;
+	return __alloc_bootmem_nopanic(size, align, BOOTMEM_LOW_LIMIT);
+}
+
 static inline void * __init memblock_virt_alloc_nopanic(
 					phys_addr_t size, phys_addr_t align)
 {
@@ -309,6 +328,14 @@ static inline void * __init memblock_virt_alloc_try_nid(phys_addr_t size,
 					  min_addr);
 }
 
+static inline void * __init memblock_virt_alloc_try_nid_raw(
+			phys_addr_t size, phys_addr_t align,
+			phys_addr_t min_addr, phys_addr_t max_addr, int nid)
+{
+	return ___alloc_bootmem_node_nopanic(NODE_DATA(nid), size, align,
+				min_addr, max_addr);
+}
+
 static inline void * __init memblock_virt_alloc_try_nid_nopanic(
 			phys_addr_t size, phys_addr_t align,
 			phys_addr_t min_addr, phys_addr_t max_addr, int nid)
diff --git a/mm/memblock.c b/mm/memblock.c
index 91205780e6b1..1f299fb1eb08 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1327,7 +1327,6 @@ static void * __init memblock_virt_alloc_internal(
 	return NULL;
 done:
 	ptr = phys_to_virt(alloc);
-	memset(ptr, 0, size);
 
 	/*
 	 * The min_count is set to 0 so that bootmem allocated blocks
@@ -1340,6 +1339,45 @@ static void * __init memblock_virt_alloc_internal(
 	return ptr;
 }
 
+/**
+ * memblock_virt_alloc_try_nid_raw - allocate boot memory block without zeroing
+ * memory and without panicking
+ * @size: size of memory block to be allocated in bytes
+ * @align: alignment of the region and block's size
+ * @min_addr: the lower bound of the memory region from where the allocation
+ *	  is preferred (phys address)
+ * @max_addr: the upper bound of the memory region from where the allocation
+ *	      is preferred (phys address), or %BOOTMEM_ALLOC_ACCESSIBLE to
+ *	      allocate only from memory limited by memblock.current_limit value
+ * @nid: nid of the free area to find, %NUMA_NO_NODE for any node
+ *
+ * Public function, provides additional debug information (including caller
+ * info), if enabled. Does not zero allocated memory, does not panic if request
+ * cannot be satisfied.
+ *
+ * RETURNS:
+ * Virtual address of allocated memory block on success, NULL on failure.
+ */
+void * __init memblock_virt_alloc_try_nid_raw(
+			phys_addr_t size, phys_addr_t align,
+			phys_addr_t min_addr, phys_addr_t max_addr,
+			int nid)
+{
+	void *ptr;
+
+	memblock_dbg("%s: %llu bytes align=0x%llx nid=%d from=0x%llx max_addr=0x%llx %pF\n",
+		     __func__, (u64)size, (u64)align, nid, (u64)min_addr,
+		     (u64)max_addr, (void *)_RET_IP_);
+
+	ptr = memblock_virt_alloc_internal(size, align,
+					   min_addr, max_addr, nid);
+#ifdef CONFIG_DEBUG_VM
+	if (ptr && size > 0)
+		memset(ptr, 0xff, size);
+#endif
+	return ptr;
+}
+
 /**
  * memblock_virt_alloc_try_nid_nopanic - allocate boot memory block
  * @size: size of memory block to be allocated in bytes
@@ -1351,8 +1389,8 @@ static void * __init memblock_virt_alloc_internal(
  *	      allocate only from memory limited by memblock.current_limit value
  * @nid: nid of the free area to find, %NUMA_NO_NODE for any node
  *
- * Public version of _memblock_virt_alloc_try_nid_nopanic() which provides
- * additional debug information (including caller info), if enabled.
+ * Public function, provides additional debug information (including caller
+ * info), if enabled. This function zeroes the allocated memory.
  *
  * RETURNS:
  * Virtual address of allocated memory block on success, NULL on failure.
@@ -1362,11 +1400,17 @@ void * __init memblock_virt_alloc_try_nid_nopanic(
 				phys_addr_t min_addr, phys_addr_t max_addr,
 				int nid)
 {
+	void *ptr;
+
 	memblock_dbg("%s: %llu bytes align=0x%llx nid=%d from=0x%llx max_addr=0x%llx %pF\n",
 		     __func__, (u64)size, (u64)align, nid, (u64)min_addr,
 		     (u64)max_addr, (void *)_RET_IP_);
-	return memblock_virt_alloc_internal(size, align, min_addr,
-					     max_addr, nid);
+
+	ptr = memblock_virt_alloc_internal(size, align,
+					   min_addr, max_addr, nid);
+	if (ptr)
+		memset(ptr, 0, size);
+	return ptr;
 }
 
 /**
@@ -1380,7 +1424,7 @@ void * __init memblock_virt_alloc_try_nid_nopanic(
  *	      allocate only from memory limited by memblock.current_limit value
  * @nid: nid of the free area to find, %NUMA_NO_NODE for any node
  *
- * Public panicking version of _memblock_virt_alloc_try_nid_nopanic()
+ * Public panicking version of memblock_virt_alloc_try_nid_nopanic()
  * which provides debug information (including caller info), if enabled,
  * and panics if the request can not be satisfied.
  *
@@ -1399,8 +1443,10 @@ void * __init memblock_virt_alloc_try_nid(
 		     (u64)max_addr, (void *)_RET_IP_);
 	ptr = memblock_virt_alloc_internal(size, align,
 					   min_addr, max_addr, nid);
-	if (ptr)
+	if (ptr) {
+		memset(ptr, 0, size);
 		return ptr;
+	}
 
 	panic("%s: Failed to allocate %llu bytes align=0x%llx nid=%d from=0x%llx max_addr=0x%llx\n",
 	      __func__, (u64)size, (u64)align, nid, (u64)min_addr,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cdbd14829fd3..20b0bace2235 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7307,18 +7307,17 @@ void *__init alloc_large_system_hash(const char *tablename,
 
 	log2qty = ilog2(numentries);
 
-	/*
-	 * memblock allocator returns zeroed memory already, so HASH_ZERO is
-	 * currently not used when HASH_EARLY is specified.
-	 */
 	gfp_flags = (flags & HASH_ZERO) ? GFP_ATOMIC | __GFP_ZERO : GFP_ATOMIC;
 	do {
 		size = bucketsize << log2qty;
-		if (flags & HASH_EARLY)
-			table = memblock_virt_alloc_nopanic(size, 0);
-		else if (hashdist)
+		if (flags & HASH_EARLY) {
+			if (flags & HASH_ZERO)
+				table = memblock_virt_alloc_nopanic(size, 0);
+			else
+				table = memblock_virt_alloc_raw(size, 0);
+		} else if (hashdist) {
 			table = __vmalloc(size, gfp_flags, PAGE_KERNEL);
-		else {
+		} else {
 			/*
 			 * If bucketsize is not a power-of-two, we may free
 			 * some pages at the end of hash table which
-- 
2.14.2

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[PATCH v10 05/10] mm: zero reserved and unavailable struct pages

[Pavel Tatashin]

Some memory is reserved but unavailable: not present in memblock.memory
(because not backed by physical pages), but present in memblock.reserved.
Such memory has backing struct pages, but they are not initialized by going
through __init_single_page().

In some cases these struct pages are accessed even if they do not contain
any data. One example is page_to_pfn() might access page->flags if this is
where section information is stored (CONFIG_SPARSEMEM,
SECTION_IN_PAGE_FLAGS).

One example of such memory: trim_low_memory_range() unconditionally
reserves from pfn 0, but e820__memblock_setup() might provide the exiting
memory from pfn 1 (i.e. KVM).

Since, struct pages are zeroed in __init_single_page(), and not during
allocation time, we must zero such struct pages explicitly.

The patch involves adding a new memblock iterator:
	for_each_resv_unavail_range(i, p_start, p_end)

Which iterates through reserved && !memory lists, and we zero struct pages
explicitly by calling mm_zero_struct_page().

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Reviewed-by: Bob Picco <bob.picco@oracle.com>
---
 include/linux/memblock.h | 16 ++++++++++++++++
 include/linux/mm.h       | 15 +++++++++++++++
 mm/page_alloc.c          | 38 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 69 insertions(+)

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index bae11c7e7bf3..ce8bfa5f3e9b 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -237,6 +237,22 @@ unsigned long memblock_next_valid_pfn(unsigned long pfn, unsigned long max_pfn);
 	for_each_mem_range_rev(i, &memblock.memory, &memblock.reserved,	\
 			       nid, flags, p_start, p_end, p_nid)
 
+/**
+ * for_each_resv_unavail_range - iterate through reserved and unavailable memory
+ * @i: u64 used as loop variable
+ * @flags: pick from blocks based on memory attributes
+ * @p_start: ptr to phys_addr_t for start address of the range, can be %NULL
+ * @p_end: ptr to phys_addr_t for end address of the range, can be %NULL
+ *
+ * Walks over unavailable but reserved (reserved && !memory) areas of memblock.
+ * Available as soon as memblock is initialized.
+ * Note: because this memory does not belong to any physical node, flags and
+ * nid arguments do not make sense and thus not exported as arguments.
+ */
+#define for_each_resv_unavail_range(i, p_start, p_end)			\
+	for_each_mem_range(i, &memblock.reserved, &memblock.memory,	\
+			   NUMA_NO_NODE, MEMBLOCK_NONE, p_start, p_end, NULL)
+
 static inline void memblock_set_region_flags(struct memblock_region *r,
 					     unsigned long flags)
 {
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 065d99deb847..04c8b2e5aff4 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -94,6 +94,15 @@ extern int mmap_rnd_compat_bits __read_mostly;
 #define mm_forbids_zeropage(X)	(0)
 #endif
 
+/*
+ * On some architectures it is expensive to call memset() for small sizes.
+ * Those architectures should provide their own implementation of "struct page"
+ * zeroing by defining this macro in <asm/pgtable.h>.
+ */
+#ifndef mm_zero_struct_page
+#define mm_zero_struct_page(pp)  ((void)memset((pp), 0, sizeof(struct page)))
+#endif
+
 /*
  * Default maximum number of active map areas, this limits the number of vmas
  * per mm struct. Users can overwrite this number by sysctl but there is a
@@ -2001,6 +2010,12 @@ extern int __meminit __early_pfn_to_nid(unsigned long pfn,
 					struct mminit_pfnnid_cache *state);
 #endif
 
+#ifdef CONFIG_HAVE_MEMBLOCK
+void zero_resv_unavail(void);
+#else
+static inline void zero_resv_unavail(void) {}
+#endif
+
 extern void set_dma_reserve(unsigned long new_dma_reserve);
 extern void memmap_init_zone(unsigned long, int, unsigned long,
 				unsigned long, enum memmap_context);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 20b0bace2235..5f0013bbbe9d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6209,6 +6209,42 @@ void __paginginit free_area_init_node(int nid, unsigned long *zones_size,
 	free_area_init_core(pgdat);
 }
 
+#ifdef CONFIG_HAVE_MEMBLOCK
+/*
+ * Only struct pages that are backed by physical memory are zeroed and
+ * initialized by going through __init_single_page(). But, there are some
+ * struct pages which are reserved in memblock allocator and their fields
+ * may be accessed (for example page_to_pfn() on some configuration accesses
+ * flags). We must explicitly zero those struct pages.
+ */
+void __paginginit zero_resv_unavail(void)
+{
+	phys_addr_t start, end;
+	unsigned long pfn;
+	u64 i, pgcnt;
+
+	/* Loop through ranges that are reserved, but do not have reported
+	 * physical memory backing.
+	 */
+	pgcnt = 0;
+	for_each_resv_unavail_range(i, &start, &end) {
+		for (pfn = PFN_DOWN(start); pfn < PFN_UP(end); pfn++) {
+			mm_zero_struct_page(pfn_to_page(pfn));
+			pgcnt++;
+		}
+	}
+
+	/*
+	 * Struct pages that do not have backing memory. This could be because
+	 * firmware is using some of this memory, or for some other reasons.
+	 * Once memblock is changed so such behaviour is not allowed: i.e.
+	 * list of "reserved" memory must be a subset of list of "memory", then
+	 * this code can be removed.
+	 */
+	pr_info("Reserved but unavailable: %lld pages", pgcnt);
+}
+#endif /* CONFIG_HAVE_MEMBLOCK */
+
 #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
 
 #if MAX_NUMNODES > 1
@@ -6632,6 +6668,7 @@ void __init free_area_init_nodes(unsigned long *max_zone_pfn)
 			node_set_state(nid, N_MEMORY);
 		check_for_memory(pgdat, nid);
 	}
+	zero_resv_unavail();
 }
 
 static int __init cmdline_parse_core(char *p, unsigned long *core)
@@ -6795,6 +6832,7 @@ void __init free_area_init(unsigned long *zones_size)
 {
 	free_area_init_node(0, zones_size,
 			__pa(PAGE_OFFSET) >> PAGE_SHIFT, NULL);
+	zero_resv_unavail();
 }
 
 static int page_alloc_cpu_dead(unsigned int cpu)
-- 
2.14.2

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[PATCH v10 06/10] mm/kasan: kasan specific map populate function

[Pavel Tatashin]

During early boot, kasan uses vmemmap_populate() to establish its shadow
memory. But, that interface is intended for struct pages use.

Because of the current project, vmemmap won't be zeroed during allocation,
but kasan expects that memory to be zeroed. We are adding a new
kasan_map_populate() function to resolve this difference.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
---
 arch/arm64/include/asm/pgtable.h |  3 ++
 include/linux/kasan.h            |  2 ++
 mm/kasan/kasan_init.c            | 67 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 72 insertions(+)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index b46e54c2399b..11ff58901519 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -381,6 +381,9 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 				 PUD_TYPE_TABLE)
 #endif
 
+#define pmd_large(pmd)		pmd_sect(pmd)
+#define pud_large(pud)		pud_sect(pud)
+
 static inline void set_pmd(pmd_t *pmdp, pmd_t pmd)
 {
 	*pmdp = pmd;
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index a5c7046f26b4..7e13df1722c2 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -78,6 +78,8 @@ size_t kasan_metadata_size(struct kmem_cache *cache);
 
 bool kasan_save_enable_multi_shot(void);
 void kasan_restore_multi_shot(bool enabled);
+int __meminit kasan_map_populate(unsigned long start, unsigned long end,
+				 int node);
 
 #else /* CONFIG_KASAN */
 
diff --git a/mm/kasan/kasan_init.c b/mm/kasan/kasan_init.c
index 554e4c0f23a2..57a973f05f63 100644
--- a/mm/kasan/kasan_init.c
+++ b/mm/kasan/kasan_init.c
@@ -197,3 +197,70 @@ void __init kasan_populate_zero_shadow(const void *shadow_start,
 		zero_p4d_populate(pgd, addr, next);
 	} while (pgd++, addr = next, addr != end);
 }
+
+/* Creates mappings for kasan during early boot. The mapped memory is zeroed */
+int __meminit kasan_map_populate(unsigned long start, unsigned long end,
+				 int node)
+{
+	unsigned long addr, pfn, next;
+	unsigned long long size;
+	pgd_t *pgd;
+	p4d_t *p4d;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+	int ret;
+
+	ret = vmemmap_populate(start, end, node);
+	/*
+	 * We might have partially populated memory, so check for no entries,
+	 * and zero only those that actually exist.
+	 */
+	for (addr = start; addr < end; addr = next) {
+		pgd = pgd_offset_k(addr);
+		if (pgd_none(*pgd)) {
+			next = pgd_addr_end(addr, end);
+			continue;
+		}
+
+		p4d = p4d_offset(pgd, addr);
+		if (p4d_none(*p4d)) {
+			next = p4d_addr_end(addr, end);
+			continue;
+		}
+
+		pud = pud_offset(p4d, addr);
+		if (pud_none(*pud)) {
+			next = pud_addr_end(addr, end);
+			continue;
+		}
+		if (pud_large(*pud)) {
+			/* This is PUD size page */
+			next = pud_addr_end(addr, end);
+			size = PUD_SIZE;
+			pfn = pud_pfn(*pud);
+		} else {
+			pmd = pmd_offset(pud, addr);
+			if (pmd_none(*pmd)) {
+				next = pmd_addr_end(addr, end);
+				continue;
+			}
+			if (pmd_large(*pmd)) {
+				/* This is PMD size page */
+				next = pmd_addr_end(addr, end);
+				size = PMD_SIZE;
+				pfn = pmd_pfn(*pmd);
+			} else {
+				pte = pte_offset_kernel(pmd, addr);
+				next = addr + PAGE_SIZE;
+				if (pte_none(*pte))
+					continue;
+				/* This is base size page */
+				size = PAGE_SIZE;
+				pfn = pte_pfn(*pte);
+			}
+		}
+		memset(phys_to_virt(PFN_PHYS(pfn)), 0, size);
+	}
+	return ret;
+}
-- 
2.14.2

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[PATCH v10 07/10] x86/kasan: use kasan_map_populate()

[Pavel Tatashin]

To optimize the performance of struct page initialization,
vmemmap_populate() will no longer zero memory.

Therefore, we must use a new interface to allocate and map kasan shadow
memory, that also zeroes memory for us.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
---
 arch/x86/mm/kasan_init_64.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index bc84b73684b7..2db95efd208e 100644
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c
@@ -23,7 +23,7 @@ static int __init map_range(struct range *range)
 	start = (unsigned long)kasan_mem_to_shadow(pfn_to_kaddr(range->start));
 	end = (unsigned long)kasan_mem_to_shadow(pfn_to_kaddr(range->end));
 
-	return vmemmap_populate(start, end, NUMA_NO_NODE);
+	return kasan_map_populate(start, end, NUMA_NO_NODE);
 }
 
 static void __init clear_pgds(unsigned long start,
@@ -136,9 +136,9 @@ void __init kasan_init(void)
 		kasan_mem_to_shadow((void *)PAGE_OFFSET + MAXMEM),
 		kasan_mem_to_shadow((void *)__START_KERNEL_map));
 
-	vmemmap_populate((unsigned long)kasan_mem_to_shadow(_stext),
-			(unsigned long)kasan_mem_to_shadow(_end),
-			NUMA_NO_NODE);
+	kasan_map_populate((unsigned long)kasan_mem_to_shadow(_stext),
+			   (unsigned long)kasan_mem_to_shadow(_end),
+			   NUMA_NO_NODE);
 
 	kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END),
 			(void *)KASAN_SHADOW_END);
-- 
2.14.2

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[PATCH v10 08/10] arm64/kasan: use kasan_map_populate()

[Pavel Tatashin]

To optimize the performance of struct page initialization,
vmemmap_populate() will no longer zero memory.

Therefore, we must use a new interface to allocate and map kasan shadow
memory, that also zeroes memory for us.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
---
 arch/arm64/mm/kasan_init.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 81f03959a4ab..b6e92cfa3ea3 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -161,11 +161,11 @@ void __init kasan_init(void)
 
 	clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 
-	vmemmap_populate(kimg_shadow_start, kimg_shadow_end,
-			 pfn_to_nid(virt_to_pfn(lm_alias(_text))));
+	kasan_map_populate(kimg_shadow_start, kimg_shadow_end,
+			   pfn_to_nid(virt_to_pfn(lm_alias(_text))));
 
 	/*
-	 * vmemmap_populate() has populated the shadow region that covers the
+	 * kasan_map_populate() has populated the shadow region that covers the
 	 * kernel image with SWAPPER_BLOCK_SIZE mappings, so we have to round
 	 * the start and end addresses to SWAPPER_BLOCK_SIZE as well, to prevent
 	 * kasan_populate_zero_shadow() from replacing the page table entries
@@ -191,9 +191,9 @@ void __init kasan_init(void)
 		if (start >= end)
 			break;
 
-		vmemmap_populate((unsigned long)kasan_mem_to_shadow(start),
-				(unsigned long)kasan_mem_to_shadow(end),
-				pfn_to_nid(virt_to_pfn(start)));
+		kasan_map_populate((unsigned long)kasan_mem_to_shadow(start),
+				   (unsigned long)kasan_mem_to_shadow(end),
+				   pfn_to_nid(virt_to_pfn(start)));
 	}
 
 	/*
-- 
2.14.2

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[PATCH v10 09/10] mm: stop zeroing memory during allocation in vmemmap

[Pavel Tatashin]

vmemmap_alloc_block() will no longer zero the block, so zero memory
at its call sites for everything except struct pages.  Struct page memory
is zero'd by struct page initialization.

Replace allocators in sprase-vmemmap to use the non-zeroing version. So,
we will get the performance improvement by zeroing the memory in parallel
when struct pages are zeroed.

Add struct page zeroing as a part of initialization of other fields in
__init_single_page().

This single thread performance collected on: Intel(R) Xeon(R) CPU E7-8895
v3 @ 2.60GHz with 1T of memory (268400646 pages in 8 nodes):

                         BASE            FIX
sparse_init     11.244671836s   0.007199623s
zone_sizes_init  4.879775891s   8.355182299s
                  --------------------------
Total           16.124447727s   8.362381922s

sparse_init is where memory for struct pages is zeroed, and the zeroing
part is moved later in this patch into __init_single_page(), which is
called from zone_sizes_init().

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Reviewed-by: Bob Picco <bob.picco@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
---
 include/linux/mm.h  | 11 +++++++++++
 mm/page_alloc.c     |  1 +
 mm/sparse-vmemmap.c | 15 +++++++--------
 mm/sparse.c         |  6 +++---
 4 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 04c8b2e5aff4..fd045a3b243a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2501,6 +2501,17 @@ static inline void *vmemmap_alloc_block_buf(unsigned long size, int node)
 	return __vmemmap_alloc_block_buf(size, node, NULL);
 }
 
+static inline void *vmemmap_alloc_block_zero(unsigned long size, int node)
+{
+	void *p = vmemmap_alloc_block(size, node);
+
+	if (!p)
+		return NULL;
+	memset(p, 0, size);
+
+	return p;
+}
+
 void vmemmap_verify(pte_t *, int, unsigned long, unsigned long);
 int vmemmap_populate_basepages(unsigned long start, unsigned long end,
 			       int node);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5f0013bbbe9d..85e038e1e941 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1170,6 +1170,7 @@ static void free_one_page(struct zone *zone,
 static void __meminit __init_single_page(struct page *page, unsigned long pfn,
 				unsigned long zone, int nid)
 {
+	mm_zero_struct_page(page);
 	set_page_links(page, zone, nid, pfn);
 	init_page_count(page);
 	page_mapcount_reset(page);
diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index d1a39b8051e0..c2f5654e7c9d 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -41,7 +41,7 @@ static void * __ref __earlyonly_bootmem_alloc(int node,
 				unsigned long align,
 				unsigned long goal)
 {
-	return memblock_virt_alloc_try_nid(size, align, goal,
+	return memblock_virt_alloc_try_nid_raw(size, align, goal,
 					    BOOTMEM_ALLOC_ACCESSIBLE, node);
 }
 
@@ -54,9 +54,8 @@ void * __meminit vmemmap_alloc_block(unsigned long size, int node)
 	if (slab_is_available()) {
 		struct page *page;
 
-		page = alloc_pages_node(node,
-			GFP_KERNEL | __GFP_ZERO | __GFP_RETRY_MAYFAIL,
-			get_order(size));
+		page = alloc_pages_node(node, GFP_KERNEL | __GFP_RETRY_MAYFAIL,
+					get_order(size));
 		if (page)
 			return page_address(page);
 		return NULL;
@@ -183,7 +182,7 @@ pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node)
 {
 	pmd_t *pmd = pmd_offset(pud, addr);
 	if (pmd_none(*pmd)) {
-		void *p = vmemmap_alloc_block(PAGE_SIZE, node);
+		void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
 		if (!p)
 			return NULL;
 		pmd_populate_kernel(&init_mm, pmd, p);
@@ -195,7 +194,7 @@ pud_t * __meminit vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node)
 {
 	pud_t *pud = pud_offset(p4d, addr);
 	if (pud_none(*pud)) {
-		void *p = vmemmap_alloc_block(PAGE_SIZE, node);
+		void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
 		if (!p)
 			return NULL;
 		pud_populate(&init_mm, pud, p);
@@ -207,7 +206,7 @@ p4d_t * __meminit vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node)
 {
 	p4d_t *p4d = p4d_offset(pgd, addr);
 	if (p4d_none(*p4d)) {
-		void *p = vmemmap_alloc_block(PAGE_SIZE, node);
+		void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
 		if (!p)
 			return NULL;
 		p4d_populate(&init_mm, p4d, p);
@@ -219,7 +218,7 @@ pgd_t * __meminit vmemmap_pgd_populate(unsigned long addr, int node)
 {
 	pgd_t *pgd = pgd_offset_k(addr);
 	if (pgd_none(*pgd)) {
-		void *p = vmemmap_alloc_block(PAGE_SIZE, node);
+		void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
 		if (!p)
 			return NULL;
 		pgd_populate(&init_mm, pgd, p);
diff --git a/mm/sparse.c b/mm/sparse.c
index 83b3bf6461af..d22f51bb7c79 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -437,9 +437,9 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
 	}
 
 	size = PAGE_ALIGN(size);
-	map = memblock_virt_alloc_try_nid(size * map_count,
-					  PAGE_SIZE, __pa(MAX_DMA_ADDRESS),
-					  BOOTMEM_ALLOC_ACCESSIBLE, nodeid);
+	map = memblock_virt_alloc_try_nid_raw(size * map_count,
+					      PAGE_SIZE, __pa(MAX_DMA_ADDRESS),
+					      BOOTMEM_ALLOC_ACCESSIBLE, nodeid);
 	if (map) {
 		for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
 			if (!present_section_nr(pnum))
-- 
2.14.2

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[PATCH v10 10/10] sparc64: optimized struct page zeroing

[Pavel Tatashin]

Add an optimized mm_zero_struct_page(), so struct page's are zeroed without
calling memset(). We do eight to ten regular stores based on the size of
struct page. Compiler optimizes out the conditions of switch() statement.

SPARC-M6 with 15T of memory, single thread performance:

                               BASE            FIX  OPTIMIZED_FIX
        bootmem_init   28.440467985s   2.305674818s   2.305161615s
free_area_init_nodes  202.845901673s 225.343084508s 172.556506560s
                      --------------------------------------------
Total                 231.286369658s 227.648759326s 174.861668175s

BASE:  current linux
FIX:   This patch series without "optimized struct page zeroing"
OPTIMIZED_FIX: This patch series including the current patch.

bootmem_init() is where memory for struct pages is zeroed during
allocation. Note, about two seconds in this function is a fixed time: it
does not increase as memory is increased.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Reviewed-by: Bob Picco <bob.picco@oracle.com>
Acked-by: David S. Miller <davem@davemloft.net>
---
 arch/sparc/include/asm/pgtable_64.h | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index 4fefe3762083..8ed478abc630 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -230,6 +230,36 @@ extern unsigned long _PAGE_ALL_SZ_BITS;
 extern struct page *mem_map_zero;
 #define ZERO_PAGE(vaddr)	(mem_map_zero)
 
+/* This macro must be updated when the size of struct page grows above 80
+ * or reduces below 64.
+ * The idea that compiler optimizes out switch() statement, and only
+ * leaves clrx instructions
+ */
+#define	mm_zero_struct_page(pp) do {					\
+	unsigned long *_pp = (void *)(pp);				\
+									\
+	 /* Check that struct page is either 64, 72, or 80 bytes */	\
+	BUILD_BUG_ON(sizeof(struct page) & 7);				\
+	BUILD_BUG_ON(sizeof(struct page) < 64);				\
+	BUILD_BUG_ON(sizeof(struct page) > 80);				\
+									\
+	switch (sizeof(struct page)) {					\
+	case 80:							\
+		_pp[9] = 0;	/* fallthrough */			\
+	case 72:							\
+		_pp[8] = 0;	/* fallthrough */			\
+	default:							\
+		_pp[7] = 0;						\
+		_pp[6] = 0;						\
+		_pp[5] = 0;						\
+		_pp[4] = 0;						\
+		_pp[3] = 0;						\
+		_pp[2] = 0;						\
+		_pp[1] = 0;						\
+		_pp[0] = 0;						\
+	}								\
+} while (0)
+
 /* PFNs are real physical page numbers.  However, mem_map only begins to record
  * per-page information starting at pfn_base.  This is to handle systems where
  * the first physical page in the machine is at some huge physical address,
-- 
2.14.2

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RE: [PATCH v10 09/10] mm: stop zeroing memory during allocation in vmemmap

[David Laight]

From: Pavel Tatashin
> Sent: 05 October 2017 22:11
> vmemmap_alloc_block() will no longer zero the block, so zero memory
> at its call sites for everything except struct pages.  Struct page memory
> is zero'd by struct page initialization.

It seems dangerous to change an allocator to stop zeroing memory.
It is probably saver to add a new function that doesn't zero
the memory and use that is the places where you don't want it
to be zeroed.

	David

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Re: [PATCH v10 09/10] mm: stop zeroing memory during allocation in vmemmap

[Michal Hocko]

On Fri 06-10-17 11:10:14, David Laight wrote:
> From: Pavel Tatashin
> > Sent: 05 October 2017 22:11
> > vmemmap_alloc_block() will no longer zero the block, so zero memory
> > at its call sites for everything except struct pages.  Struct page memory
> > is zero'd by struct page initialization.
> 
> It seems dangerous to change an allocator to stop zeroing memory.
> It is probably saver to add a new function that doesn't zero
> the memory and use that is the places where you don't want it
> to be zeroed.

Not sure what you mean. memblock_virt_alloc_try_nid_raw is a new
function which doesn't zero out...
-- 
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SUSE Labs

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RE: [PATCH v10 09/10] mm: stop zeroing memory during allocation in vmemmap

[David Laight]

From: Michal Hocko
> Sent: 06 October 2017 12:47
> On Fri 06-10-17 11:10:14, David Laight wrote:
> > From: Pavel Tatashin
> > > Sent: 05 October 2017 22:11
> > > vmemmap_alloc_block() will no longer zero the block, so zero memory
> > > at its call sites for everything except struct pages.  Struct page memory
> > > is zero'd by struct page initialization.
> >
> > It seems dangerous to change an allocator to stop zeroing memory.
> > It is probably saver to add a new function that doesn't zero
> > the memory and use that is the places where you don't want it
> > to be zeroed.
> 
> Not sure what you mean. memblock_virt_alloc_try_nid_raw is a new
> function which doesn't zero out...

You should probably leave vmemap_alloc_block() zeroing the memory
so that existing alls don't have to be changed - apart from the
ones you are explicitly optimising.

	David

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Re: [PATCH v10 09/10] mm: stop zeroing memory during allocation in vmemmap

[Michal Hocko]

On Fri 06-10-17 12:11:42, David Laight wrote:
> From: Michal Hocko
> > Sent: 06 October 2017 12:47
> > On Fri 06-10-17 11:10:14, David Laight wrote:
> > > From: Pavel Tatashin
> > > > Sent: 05 October 2017 22:11
> > > > vmemmap_alloc_block() will no longer zero the block, so zero memory
> > > > at its call sites for everything except struct pages.  Struct page memory
> > > > is zero'd by struct page initialization.
> > >
> > > It seems dangerous to change an allocator to stop zeroing memory.
> > > It is probably saver to add a new function that doesn't zero
> > > the memory and use that is the places where you don't want it
> > > to be zeroed.
> > 
> > Not sure what you mean. memblock_virt_alloc_try_nid_raw is a new
> > function which doesn't zero out...
> 
> You should probably leave vmemap_alloc_block() zeroing the memory
> so that existing alls don't have to be changed - apart from the
> ones you are explicitly optimising.

But the whole point of vmemmap_alloc_block is to allocate memmaps and
the point of this change is to cover those. This is not a generic API
that other users would depend on. 
-- 
Michal Hocko
SUSE Labs

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Re: [PATCH v10 05/10] mm: zero reserved and unavailable struct pages

[Michal Hocko]

On Thu 05-10-17 17:11:19, Pavel Tatashin wrote:
> Some memory is reserved but unavailable: not present in memblock.memory
> (because not backed by physical pages), but present in memblock.reserved.
> Such memory has backing struct pages, but they are not initialized by going
> through __init_single_page().
> 
> In some cases these struct pages are accessed even if they do not contain
> any data. One example is page_to_pfn() might access page->flags if this is
> where section information is stored (CONFIG_SPARSEMEM,
> SECTION_IN_PAGE_FLAGS).
> 
> One example of such memory: trim_low_memory_range() unconditionally
> reserves from pfn 0, but e820__memblock_setup() might provide the exiting
> memory from pfn 1 (i.e. KVM).
> 
> Since, struct pages are zeroed in __init_single_page(), and not during
> allocation time, we must zero such struct pages explicitly.
> 
> The patch involves adding a new memblock iterator:
> 	for_each_resv_unavail_range(i, p_start, p_end)
> 
> Which iterates through reserved && !memory lists, and we zero struct pages
> explicitly by calling mm_zero_struct_page().

As I've said in other reply this should go in only if the scenario you
describe is real. I am somehow suspicious to be honest. I simply do not
see how those weird struct pages would be in a valid pfn range of any
zone.

> Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
> Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
> Reviewed-by: Bob Picco <bob.picco@oracle.com>
> ---
>  include/linux/memblock.h | 16 ++++++++++++++++
>  include/linux/mm.h       | 15 +++++++++++++++
>  mm/page_alloc.c          | 38 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 69 insertions(+)
> 
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index bae11c7e7bf3..ce8bfa5f3e9b 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -237,6 +237,22 @@ unsigned long memblock_next_valid_pfn(unsigned long pfn, unsigned long max_pfn);
>  	for_each_mem_range_rev(i, &memblock.memory, &memblock.reserved,	\
>  			       nid, flags, p_start, p_end, p_nid)
>  
> +/**
> + * for_each_resv_unavail_range - iterate through reserved and unavailable memory
> + * @i: u64 used as loop variable
> + * @flags: pick from blocks based on memory attributes
> + * @p_start: ptr to phys_addr_t for start address of the range, can be %NULL
> + * @p_end: ptr to phys_addr_t for end address of the range, can be %NULL
> + *
> + * Walks over unavailable but reserved (reserved && !memory) areas of memblock.
> + * Available as soon as memblock is initialized.
> + * Note: because this memory does not belong to any physical node, flags and
> + * nid arguments do not make sense and thus not exported as arguments.
> + */
> +#define for_each_resv_unavail_range(i, p_start, p_end)			\
> +	for_each_mem_range(i, &memblock.reserved, &memblock.memory,	\
> +			   NUMA_NO_NODE, MEMBLOCK_NONE, p_start, p_end, NULL)
> +
>  static inline void memblock_set_region_flags(struct memblock_region *r,
>  					     unsigned long flags)
>  {
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 065d99deb847..04c8b2e5aff4 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -94,6 +94,15 @@ extern int mmap_rnd_compat_bits __read_mostly;
>  #define mm_forbids_zeropage(X)	(0)
>  #endif
>  
> +/*
> + * On some architectures it is expensive to call memset() for small sizes.
> + * Those architectures should provide their own implementation of "struct page"
> + * zeroing by defining this macro in <asm/pgtable.h>.
> + */
> +#ifndef mm_zero_struct_page
> +#define mm_zero_struct_page(pp)  ((void)memset((pp), 0, sizeof(struct page)))
> +#endif
> +
>  /*
>   * Default maximum number of active map areas, this limits the number of vmas
>   * per mm struct. Users can overwrite this number by sysctl but there is a
> @@ -2001,6 +2010,12 @@ extern int __meminit __early_pfn_to_nid(unsigned long pfn,
>  					struct mminit_pfnnid_cache *state);
>  #endif
>  
> +#ifdef CONFIG_HAVE_MEMBLOCK
> +void zero_resv_unavail(void);
> +#else
> +static inline void zero_resv_unavail(void) {}
> +#endif
> +
>  extern void set_dma_reserve(unsigned long new_dma_reserve);
>  extern void memmap_init_zone(unsigned long, int, unsigned long,
>  				unsigned long, enum memmap_context);
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 20b0bace2235..5f0013bbbe9d 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6209,6 +6209,42 @@ void __paginginit free_area_init_node(int nid, unsigned long *zones_size,
>  	free_area_init_core(pgdat);
>  }
>  
> +#ifdef CONFIG_HAVE_MEMBLOCK
> +/*
> + * Only struct pages that are backed by physical memory are zeroed and
> + * initialized by going through __init_single_page(). But, there are some
> + * struct pages which are reserved in memblock allocator and their fields
> + * may be accessed (for example page_to_pfn() on some configuration accesses
> + * flags). We must explicitly zero those struct pages.
> + */
> +void __paginginit zero_resv_unavail(void)
> +{
> +	phys_addr_t start, end;
> +	unsigned long pfn;
> +	u64 i, pgcnt;
> +
> +	/* Loop through ranges that are reserved, but do not have reported
> +	 * physical memory backing.
> +	 */
> +	pgcnt = 0;
> +	for_each_resv_unavail_range(i, &start, &end) {
> +		for (pfn = PFN_DOWN(start); pfn < PFN_UP(end); pfn++) {
> +			mm_zero_struct_page(pfn_to_page(pfn));
> +			pgcnt++;
> +		}
> +	}
> +
> +	/*
> +	 * Struct pages that do not have backing memory. This could be because
> +	 * firmware is using some of this memory, or for some other reasons.
> +	 * Once memblock is changed so such behaviour is not allowed: i.e.
> +	 * list of "reserved" memory must be a subset of list of "memory", then
> +	 * this code can be removed.
> +	 */
> +	pr_info("Reserved but unavailable: %lld pages", pgcnt);
> +}
> +#endif /* CONFIG_HAVE_MEMBLOCK */
> +
>  #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
>  
>  #if MAX_NUMNODES > 1
> @@ -6632,6 +6668,7 @@ void __init free_area_init_nodes(unsigned long *max_zone_pfn)
>  			node_set_state(nid, N_MEMORY);
>  		check_for_memory(pgdat, nid);
>  	}
> +	zero_resv_unavail();
>  }
>  
>  static int __init cmdline_parse_core(char *p, unsigned long *core)
> @@ -6795,6 +6832,7 @@ void __init free_area_init(unsigned long *zones_size)
>  {
>  	free_area_init_node(0, zones_size,
>  			__pa(PAGE_OFFSET) >> PAGE_SHIFT, NULL);
> +	zero_resv_unavail();
>  }
>  
>  static int page_alloc_cpu_dead(unsigned int cpu)
> -- 
> 2.14.2

-- 
Michal Hocko
SUSE Labs

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Re: [PATCH v10 05/10] mm: zero reserved and unavailable struct pages

[Pasha Tatashin]

Hi Michal,

> 
> As I've said in other reply this should go in only if the scenario you
> describe is real. I am somehow suspicious to be honest. I simply do not
> see how those weird struct pages would be in a valid pfn range of any
> zone.
> 

There are examples of both when unavailable memory is not part of any 
zone, and where it is part of zones.

I run Linux in kvm with these arguments:

         qemu-system-x86_64
         -enable-kvm
         -cpu kvm64
         -kernel $kernel
         -initrd $initrd
         -m 512
         -smp 2
         -device e1000,netdev=net0
         -netdev user,id=net0
         -boot order=nc
         -no-reboot
         -watchdog i6300esb
         -watchdog-action debug
         -rtc base=localtime
         -serial stdio
         -display none
         -monitor null

This patch reports that there are 98 unavailable pages.

They are: pfn 0 and pfns in range [159, 255].

Note, trim_low_memory_range() reserves only pfns in range [0, 15], it 
does not reserve [159, 255] ones.

e820__memblock_setup() reports linux that the following physical ranges 
are available:
     [1 , 158]
[256, 130783]

Notice, that exactly unavailable pfns are missing!

Now, lets check what we have in zone 0: [1, 131039]

pfn 0, is not part of the zone, but pfns [1, 158], are.

However, the bigger problem we have if we do not initialize these struct 
pages is with memory hotplug. Because, that path operates at 2M 
boundaries (section_nr). And checks if 2M range of pages is hot 
removable. It starts with first pfn from zone, rounds it down to 2M 
boundary (sturct pages are allocated at 2M boundaries when vmemmap is 
created), and and checks if that section is hot removable. In this case 
start with pfn 1 and convert it down to pfn 0.

Later pfn is converted to struct page, and some fields are checked. Now, 
if we do not zero struct pages, we get unpredictable results. In fact 
when CONFIG_VM_DEBUG is enabled, and we explicitly set all vmemmap 
memory to ones, I am getting the following panic with kernel test 
without this patch applied:

[   23.277793] BUG: unable to handle kernel NULL pointer dereference at 
          (null)
[   23.278863] IP: is_pageblock_removable_nolock+0x35/0x90
[   23.279619] PGD 0 P4D 0
[   23.280031] Oops: 0000 [#1] PREEMPT
[   23.280527] CPU: 0 PID: 249 Comm: udevd Not tainted 
4.14.0-rc3_pt_memset10-00335-g5e2c7478bed5-dirty #8
[   23.281735] task: ffff88001f4e2900 task.stack: ffffc90000314000
[   23.282532] RIP: 0010:is_pageblock_removable_nolock+0x35/0x90
[   23.283275] RSP: 0018:ffffc90000317d60 EFLAGS: 00010202
[   23.283948] RAX: ffffffffffffffff RBX: ffff88001d92b000 RCX: 
0000000000000000
[   23.284862] RDX: 0000000000000000 RSI: 0000000000200000 RDI: 
ffff88001d92b000
[   23.285771] RBP: ffffc90000317d80 R08: 00000000000010c8 R09: 
0000000000000000
[   23.286542] R10: 0000000000000000 R11: 0000000000000000 R12: 
ffff88001db2b000
[   23.287264] R13: ffffffff81af6d00 R14: ffff88001f7d5000 R15: 
ffffffff82a1b6c0
[   23.287971] FS:  00007f4eb857f7c0(0000) GS:ffffffff81c27000(0000) 
knlGS:0000000000000000
[   23.288775] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   23.289355] CR2: 0000000000000000 CR3: 000000001f4e6000 CR4: 
00000000000006b0
[   23.290066] Call Trace:
[   23.290323]  ? is_mem_section_removable+0x5a/0xd0
[   23.290798]  show_mem_removable+0x6b/0xa0
[   23.291204]  dev_attr_show+0x1b/0x50
[   23.291565]  sysfs_kf_seq_show+0xa1/0x100
[   23.291967]  kernfs_seq_show+0x22/0x30
[   23.292349]  seq_read+0x1ac/0x3a0
[   23.292687]  kernfs_fop_read+0x36/0x190
[   23.293074]  ? security_file_permission+0x90/0xb0
[   23.293547]  __vfs_read+0x16/0x30
[   23.293884]  vfs_read+0x81/0x130
[   23.294214]  SyS_read+0x44/0xa0
[   23.294537]  entry_SYSCALL_64_fastpath+0x1f/0xbd
[   23.295003] RIP: 0033:0x7f4eb7c660a0
[   23.295364] RSP: 002b:00007ffda6cffe28 EFLAGS: 00000246 ORIG_RAX: 
0000000000000000
[   23.296152] RAX: ffffffffffffffda RBX: 00000000000003de RCX: 
00007f4eb7c660a0
[   23.296934] RDX: 0000000000001000 RSI: 00007ffda6cffec8 RDI: 
0000000000000005
[   23.297963] RBP: 00007ffda6cffde8 R08: 7379732f73656369 R09: 
6f6d656d2f6d6574
[   23.299198] R10: 726f6d656d2f7972 R11: 0000000000000246 R12: 
0000000000000022
[   23.300400] R13: 0000561d68ea7710 R14: 0000000000000000 R15: 
00007ffda6d05c78
[   23.301591] Code: c1 ea 35 49 c1 e8 2b 48 8b 14 d5 c0 b6 a1 82 41 83 
e0 03 48 85 d2 74 0c 48 c1 e8 29 25 f0 0f 00 00 48 01 c2 4d 69 c0 98 
05 00 00 <48> 8b 02 48 89 fa 48 83 e0 f8 49 8b 88 28 b5 d3 81 48 29 c2 49
[   23.304739] RIP: is_pageblock_removable_nolock+0x35/0x90 RSP: 
ffffc90000317d60
[   23.305940] CR2: 0000000000000000

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Re: [PATCH v10 05/10] mm: zero reserved and unavailable struct pages

[Michal Hocko]

On Fri 06-10-17 11:25:16, Pasha Tatashin wrote:
> Hi Michal,
> 
> > 
> > As I've said in other reply this should go in only if the scenario you
> > describe is real. I am somehow suspicious to be honest. I simply do not
> > see how those weird struct pages would be in a valid pfn range of any
> > zone.
> > 
> 
> There are examples of both when unavailable memory is not part of any zone,
> and where it is part of zones.
> 
> I run Linux in kvm with these arguments:
> 
>         qemu-system-x86_64
>         -enable-kvm
>         -cpu kvm64
>         -kernel $kernel
>         -initrd $initrd
>         -m 512
>         -smp 2
>         -device e1000,netdev=net0
>         -netdev user,id=net0
>         -boot order=nc
>         -no-reboot
>         -watchdog i6300esb
>         -watchdog-action debug
>         -rtc base=localtime
>         -serial stdio
>         -display none
>         -monitor null
> 
> This patch reports that there are 98 unavailable pages.
> 
> They are: pfn 0 and pfns in range [159, 255].
> 
> Note, trim_low_memory_range() reserves only pfns in range [0, 15], it does
> not reserve [159, 255] ones.
> 
> e820__memblock_setup() reports linux that the following physical ranges are
> available:
>     [1 , 158]
> [256, 130783]
> 
> Notice, that exactly unavailable pfns are missing!
> 
> Now, lets check what we have in zone 0: [1, 131039]
> 
> pfn 0, is not part of the zone, but pfns [1, 158], are.
> 
> However, the bigger problem we have if we do not initialize these struct
> pages is with memory hotplug. Because, that path operates at 2M boundaries
> (section_nr). And checks if 2M range of pages is hot removable. It starts
> with first pfn from zone, rounds it down to 2M boundary (sturct pages are
> allocated at 2M boundaries when vmemmap is created), and and checks if that
> section is hot removable. In this case start with pfn 1 and convert it down
> to pfn 0.

Hmm, this is really interesting! I thought each memblock is guaranteed
to be section size aligned. But I suspect this is more of a wishful
thinking. But now I see what is the problem.
-- 
Michal Hocko
SUSE Labs

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