diff mbox series

mm/page_ext: Do not allocate space for page_ext->flags if not needed

Message ID 20230111215906.2645056-1-pasha.tatashin@soleen.com
State New
Headers
Series mm/page_ext: Do not allocate space for page_ext->flags if not needed |

Commit Message

Pasha Tatashin Jan. 11, 2023, 9:59 p.m. UTC 
  There is 8 byte page_ext->flags field allocated per page whenever
CONFIG_PAGE_EXTENSION is enabled. However, not every user of page_ext
uses flags. Therefore, check whether flags is needed at least by one
user and if so allocate space for it.

For example when page_table_check is enabled, on a machine with 128G
of memory before the fix:

[    2.244288] allocated 536870912 bytes of page_ext
after the fix:
[    2.160154] allocated 268435456 bytes of page_ext

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
 include/linux/page_ext.h |  7 +++++++
 mm/page_ext.c            | 12 +++++++++++-
 mm/page_owner.c          |  1 +
 mm/page_table_check.c    |  1 +
 4 files changed, 20 insertions(+), 1 deletion(-)

Comments

kernel test robot Jan. 12, 2023, 3:17 a.m. UTC | #1 
Hi Pasha,

I love your patch! Yet something to improve:

[auto build test ERROR on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/Pasha-Tatashin/mm-page_ext-Do-not-allocate-space-for-page_ext-flags-if-not-needed/20230112-055942
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20230111215906.2645056-1-pasha.tatashin%40soleen.com
patch subject: [PATCH] mm/page_ext: Do not allocate space for page_ext->flags if not needed
config: hexagon-randconfig-r012-20230110
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 8d9828ef5aa9688500657d36cd2aefbe12bbd162)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/f195fe7b408dd821eef3d052e8ebd50cccb3df51
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Pasha-Tatashin/mm-page_ext-Do-not-allocate-space-for-page_ext-flags-if-not-needed/20230112-055942
        git checkout f195fe7b408dd821eef3d052e8ebd50cccb3df51
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   In file included from mm/page_owner.c:6:
   In file included from include/linux/memblock.h:13:
   In file included from arch/hexagon/include/asm/dma.h:9:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:547:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __raw_readb(PCI_IOBASE + addr);
                             ~~~~~~~~~~ ^
   include/asm-generic/io.h:560:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:37:51: note: expanded from macro '__le16_to_cpu'
   #define __le16_to_cpu(x) ((__force __u16)(__le16)(x))
                                                     ^
   In file included from mm/page_owner.c:6:
   In file included from include/linux/memblock.h:13:
   In file included from arch/hexagon/include/asm/dma.h:9:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:573:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:35:51: note: expanded from macro '__le32_to_cpu'
   #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
                                                     ^
   In file included from mm/page_owner.c:6:
   In file included from include/linux/memblock.h:13:
   In file included from arch/hexagon/include/asm/dma.h:9:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:584:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writeb(value, PCI_IOBASE + addr);
                               ~~~~~~~~~~ ^
   include/asm-generic/io.h:594:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   include/asm-generic/io.h:604:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
>> mm/page_owner.c:102:3: error: field designator 'using_shared_flags' does not refer to any field in type 'struct page_ext_operations'; did you mean 'using_shared_ext_flags'?
           .using_shared_flags = true,
            ^~~~~~~~~~~~~~~~~~
            using_shared_ext_flags
   include/linux/page_ext.h:15:7: note: 'using_shared_ext_flags' declared here
           bool using_shared_ext_flags;
                ^
   6 warnings and 1 error generated.


vim +102 mm/page_owner.c

    97	
    98	struct page_ext_operations page_owner_ops = {
    99		.size = sizeof(struct page_owner),
   100		.need = need_page_owner,
   101		.init = init_page_owner,
 > 102		.using_shared_flags = true,
   103	};
   104
diff mbox series

Patch

diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h
index 22be4582faae..29909e135052 100644
--- a/include/linux/page_ext.h
+++ b/include/linux/page_ext.h
@@ -12,10 +12,14 @@  struct page_ext_operations {
 	size_t size;
 	bool (*need)(void);
 	void (*init)(void);
+	bool using_shared_ext_flags;
 };
 
 #ifdef CONFIG_PAGE_EXTENSION
 
+/*
+ * The page_ext_flags users must set using_shared_ext_flags to true.
+ */
 enum page_ext_flags {
 	PAGE_EXT_OWNER,
 	PAGE_EXT_OWNER_ALLOCATED,
@@ -31,6 +35,9 @@  enum page_ext_flags {
  * page_ext helps us add more information about the page.
  * All page_ext are allocated at boot or memory hotplug event,
  * then the page_ext for pfn always exists.
+ * Note: that if none of the users of page_ext is setting
+ * using_shared_ext_flags to true, the field cannot be used,
+ * as it will be overlapped with another data.
  */
 struct page_ext {
 	unsigned long flags;
diff --git a/mm/page_ext.c b/mm/page_ext.c
index 4ee522fd381c..7443a797b96b 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -71,6 +71,7 @@  static bool need_page_idle(void)
 }
 static struct page_ext_operations page_idle_ops __initdata = {
 	.need = need_page_idle,
+	.using_shared_ext_flags = true,
 };
 #endif
 
@@ -86,7 +87,7 @@  static struct page_ext_operations *page_ext_ops[] __initdata = {
 #endif
 };
 
-unsigned long page_ext_size = sizeof(struct page_ext);
+unsigned long page_ext_size;
 
 static unsigned long total_usage;
 static struct page_ext *lookup_page_ext(const struct page *page);
@@ -105,6 +106,15 @@  static bool __init invoke_need_callbacks(void)
 	int entries = ARRAY_SIZE(page_ext_ops);
 	bool need = false;
 
+	for (i = 0; i < entries; i++) {
+		if (page_ext_ops[i]->need && page_ext_ops[i]->need()) {
+			if (page_ext_ops[i]->using_shared_ext_flags) {
+				page_ext_size = sizeof(struct page_ext);
+				break;
+			}
+		}
+	}
+
 	for (i = 0; i < entries; i++) {
 		if (page_ext_ops[i]->need && page_ext_ops[i]->need()) {
 			page_ext_ops[i]->offset = page_ext_size;
diff --git a/mm/page_owner.c b/mm/page_owner.c
index 2d27f532df4c..612a988373cc 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -99,6 +99,7 @@  struct page_ext_operations page_owner_ops = {
 	.size = sizeof(struct page_owner),
 	.need = need_page_owner,
 	.init = init_page_owner,
+	.using_shared_flags = true,
 };
 
 static inline struct page_owner *get_page_owner(struct page_ext *page_ext)
diff --git a/mm/page_table_check.c b/mm/page_table_check.c
index 93e633c1d587..74cfe89d5f53 100644
--- a/mm/page_table_check.c
+++ b/mm/page_table_check.c
@@ -45,6 +45,7 @@  struct page_ext_operations page_table_check_ops = {
 	.size = sizeof(struct page_table_check),
 	.need = need_page_table_check,
 	.init = init_page_table_check,
+	.using_shared_ext_flags = false,
 };
 
 static struct page_table_check *get_page_table_check(struct page_ext *page_ext)