Slab allocators: define common size limitations

Currently we have a maze of configuration variables that determine the
maximum slab size.  Worst of all it seems to vary between SLAB and SLUB.

So define a common maximum size for kmalloc.  For conveniences sake we use
the maximum size ever supported which is 32 MB.  We limit the maximum size
to a lower limit if MAX_ORDER does not allow such large allocations.

For many architectures this patch will have the effect of adding large
kmalloc sizes.  x86_64 adds 5 new kmalloc sizes.  So a small amount of
memory will be needed for these caches (contemporary SLAB has dynamically
sizeable node and cpu structure so the waste is less than in the past)

Most architectures will then be able to allocate object with sizes up to
MAX_ORDER.  We have had repeated breakage (in fact whenever we doubled the
number of supported processors) on IA64 because one or the other struct
grew beyond what the slab allocators supported.  This will avoid future
issues and f.e.  avoid fixes for 2k and 4k cpu support.

CONFIG_LARGE_ALLOCS is no longer necessary so drop it.

It fixes sparc64 with SLAB.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/blackfin/Kconfig b/arch/blackfin/Kconfig
index 1a493050932579f460dac6d77acd2d0c3fafc7e8..d80e5b1d686e2319178b4dd94cf9801938ca1777 100644 (file)
--- a/arch/blackfin/Kconfig
+++ b/arch/blackfin/Kconfig
@@ -560,14 +560,6 @@ endchoice
 
 source "mm/Kconfig"
 
-config LARGE_ALLOCS
-       bool "Allow allocating large blocks (> 1MB) of memory"
-       help
-         Allow the slab memory allocator to keep chains for very large
-         memory sizes - upto 32MB. You may need this if your system has
-         a lot of RAM, and you need to able to allocate very large
-         contiguous chunks. If unsure, say N.
-
 config BFIN_DMA_5XX
        bool "Enable DMA Support"
        depends on (BF533 || BF532 || BF531 || BF537 || BF536 || BF534 || BF561)

diff --git a/arch/frv/Kconfig b/arch/frv/Kconfig
index 114738a4558280b264eed8589d91618352320a87..74eef7111f2bd429e60d93e1a5d021dd3ca5f50d 100644 (file)
--- a/arch/frv/Kconfig
+++ b/arch/frv/Kconfig
@@ -102,14 +102,6 @@ config HIGHPTE
          with a lot of RAM, this can be wasteful of precious low memory.
          Setting this option will put user-space page tables in high memory.
 
-config LARGE_ALLOCS
-       bool "Allow allocating large blocks (> 1MB) of memory"
-       help
-         Allow the slab memory allocator to keep chains for very large memory
-         sizes - up to 32MB. You may need this if your system has a lot of
-         RAM, and you need to able to allocate very large contiguous chunks.
-         If unsure, say N.
-
 source "mm/Kconfig"
 
 choice

diff --git a/arch/m68knommu/Kconfig b/arch/m68knommu/Kconfig
index 823f73736bb5b3c8a35f84e608302224e3abcedd..adc64a2bafbbdfb748a4d9a03801dabcf8a83ef7 100644 (file)
--- a/arch/m68knommu/Kconfig
+++ b/arch/m68knommu/Kconfig
@@ -470,14 +470,6 @@ config AVNET
        default y
        depends on (AVNET5282)
 
-config LARGE_ALLOCS
-       bool "Allow allocating large blocks (> 1MB) of memory"
-       help
-         Allow the slab memory allocator to keep chains for very large
-         memory sizes - upto 32MB. You may need this if your system has
-         a lot of RAM, and you need to able to allocate very large
-         contiguous chunks. If unsure, say N.
-
 config 4KSTACKS
        bool "Use 4Kb for kernel stacks instead of 8Kb"
        default y

diff --git a/arch/v850/Kconfig b/arch/v850/Kconfig
index 5f54c1236c18daa5809aaf461d25119bd2fcfdc8..ace479ab273ff329cc387ce536e8598f171054b4 100644 (file)
--- a/arch/v850/Kconfig
+++ b/arch/v850/Kconfig
@@ -240,14 +240,6 @@ menu "Processor type and features"
    config RESET_GUARD
          bool "Reset Guard"
 
-   config LARGE_ALLOCS
-         bool "Allow allocating large blocks (> 1MB) of memory"
-         help
-            Allow the slab memory allocator to keep chains for very large
-            memory sizes - upto 32MB. You may need this if your system has
-            a lot of RAM, and you need to able to allocate very large
-            contiguous chunks. If unsure, say N.
-
 source "mm/Kconfig"
 
 endmenu

diff --git a/include/linux/kmalloc_sizes.h b/include/linux/kmalloc_sizes.h
index bda23e00ed710e634152be31f4c1db207cca0721..e576b848ce10f8073dae6eefea4915c408b2601c 100644 (file)
--- a/include/linux/kmalloc_sizes.h
+++ b/include/linux/kmalloc_sizes.h
@@ -19,17 +19,27 @@
        CACHE(32768)
        CACHE(65536)
        CACHE(131072)
-#if (NR_CPUS > 512) || (MAX_NUMNODES > 256) || !defined(CONFIG_MMU)
+#if KMALLOC_MAX_SIZE >= 262144
        CACHE(262144)
 #endif
-#ifndef CONFIG_MMU
+#if KMALLOC_MAX_SIZE >= 524288
        CACHE(524288)
+#endif
+#if KMALLOC_MAX_SIZE >= 1048576
        CACHE(1048576)
-#ifdef CONFIG_LARGE_ALLOCS
+#endif
+#if KMALLOC_MAX_SIZE >= 2097152
        CACHE(2097152)
+#endif
+#if KMALLOC_MAX_SIZE >= 4194304
        CACHE(4194304)
+#endif
+#if KMALLOC_MAX_SIZE >= 8388608
        CACHE(8388608)
+#endif
+#if KMALLOC_MAX_SIZE >= 16777216
        CACHE(16777216)
+#endif
+#if KMALLOC_MAX_SIZE >= 33554432
        CACHE(33554432)
-#endif /* CONFIG_LARGE_ALLOCS */
-#endif /* CONFIG_MMU */
+#endif

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 6fb2ae214152b5e8b733eaceb2748e4af79d807f..a015236cc572b8f11a52bcea9ebf9a23251be934 100644 (file)
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -73,6 +73,21 @@ static inline void *kmem_cache_alloc_node(struct kmem_cache *cachep,
 }
 #endif
 
+/*
+ * The largest kmalloc size supported by the slab allocators is
+ * 32 megabyte (2^25) or the maximum allocatable page order if that is
+ * less than 32 MB.
+ *
+ * WARNING: Its not easy to increase this value since the allocators have
+ * to do various tricks to work around compiler limitations in order to
+ * ensure proper constant folding.
+ */
+#define KMALLOC_SHIFT_HIGH     ((MAX_ORDER + PAGE_SHIFT) <= 25 ? \
+                               (MAX_ORDER + PAGE_SHIFT) : 25)
+
+#define KMALLOC_MAX_SIZE       (1UL << KMALLOC_SHIFT_HIGH)
+#define KMALLOC_MAX_ORDER      (KMALLOC_SHIFT_HIGH - PAGE_SHIFT)
+
 /*
  * Common kmalloc functions provided by all allocators
  */

diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index a9fb92862aaa360a4b8ad3f4112ed271e076ec74..0764c829d967ab8c1841cddf79ba51204956e4a8 100644 (file)
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -58,17 +58,6 @@ struct kmem_cache {
  */
 #define KMALLOC_SHIFT_LOW 3
 
-#ifdef CONFIG_LARGE_ALLOCS
-#define KMALLOC_SHIFT_HIGH ((MAX_ORDER + PAGE_SHIFT) =< 25 ? \
-                               (MAX_ORDER + PAGE_SHIFT - 1) : 25)
-#else
-#if !defined(CONFIG_MMU) || NR_CPUS > 512 || MAX_NUMNODES > 256
-#define KMALLOC_SHIFT_HIGH 20
-#else
-#define KMALLOC_SHIFT_HIGH 18
-#endif
-#endif
-
 /*
  * We keep the general caches in an array of slab caches that are used for
  * 2^x bytes of allocations.
@@ -79,7 +68,7 @@ extern struct kmem_cache kmalloc_caches[KMALLOC_SHIFT_HIGH + 1];
  * Sorry that the following has to be that ugly but some versions of GCC
  * have trouble with constant propagation and loops.
  */
-static inline int kmalloc_index(int size)
+static inline int kmalloc_index(size_t size)
 {
        /*
         * We should return 0 if size == 0 but we use the smallest object
@@ -87,7 +76,7 @@ static inline int kmalloc_index(int size)
         */
        WARN_ON_ONCE(size == 0);
 
-       if (size > (1 << KMALLOC_SHIFT_HIGH))
+       if (size > KMALLOC_MAX_SIZE)
                return -1;
 
        if (size > 64 && size <= 96)
@@ -110,17 +99,13 @@ static inline int kmalloc_index(int size)
        if (size <=  64 * 1024) return 16;
        if (size <= 128 * 1024) return 17;
        if (size <= 256 * 1024) return 18;
-#if KMALLOC_SHIFT_HIGH > 18
        if (size <=  512 * 1024) return 19;
        if (size <= 1024 * 1024) return 20;
-#endif
-#if KMALLOC_SHIFT_HIGH > 20
        if (size <=  2 * 1024 * 1024) return 21;
        if (size <=  4 * 1024 * 1024) return 22;
        if (size <=  8 * 1024 * 1024) return 23;
        if (size <= 16 * 1024 * 1024) return 24;
        if (size <= 32 * 1024 * 1024) return 25;
-#endif
        return -1;
 
 /*

diff --git a/mm/slab.c b/mm/slab.c
index 1dc0ce1d0d5ddc81c10c95c10e283dc909a6a3b4..528243e15cc80079af034d9d035b1f8b6799bf86 100644 (file)
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -568,21 +568,6 @@ static void **dbg_userword(struct kmem_cache *cachep, void *objp)
 
 #endif
 
-/*
- * Maximum size of an obj (in 2^order pages) and absolute limit for the gfp
- * order.
- */
-#if defined(CONFIG_LARGE_ALLOCS)
-#define        MAX_OBJ_ORDER   13      /* up to 32Mb */
-#define        MAX_GFP_ORDER   13      /* up to 32Mb */
-#elif defined(CONFIG_MMU)
-#define        MAX_OBJ_ORDER   5       /* 32 pages */
-#define        MAX_GFP_ORDER   5       /* 32 pages */
-#else
-#define        MAX_OBJ_ORDER   8       /* up to 1Mb */
-#define        MAX_GFP_ORDER   8       /* up to 1Mb */
-#endif
-
 /*
  * Do not go above this order unless 0 objects fit into the slab.
  */
@@ -2002,7 +1987,7 @@ static size_t calculate_slab_order(struct kmem_cache *cachep,
        size_t left_over = 0;
        int gfporder;
 
-       for (gfporder = 0; gfporder <= MAX_GFP_ORDER; gfporder++) {
+       for (gfporder = 0; gfporder <= KMALLOC_MAX_ORDER; gfporder++) {
                unsigned int num;
                size_t remainder;
 
@@ -2148,7 +2133,7 @@ kmem_cache_create (const char *name, size_t size, size_t align,
         * Sanity checks... these are all serious usage bugs.
         */
        if (!name || in_interrupt() || (size < BYTES_PER_WORD) ||
-           (size > (1 << MAX_OBJ_ORDER) * PAGE_SIZE) || dtor) {
+           size > KMALLOC_MAX_SIZE || dtor) {
                printk(KERN_ERR "%s: Early error in slab %s\n", __FUNCTION__,
                                name);
                BUG();