[PATCH] slob: poor man's NUMA support.

Paul Mundt
2007-06-19T09:08:04Z

This adds preliminary NUMA support to SLOB, primarily aimed at systems
with small nodes (tested all the way down to a 128kB SRAM block), whether
asymmetric or otherwise.

We follow the same conventions as SLAB/SLUB, preferring current node
placement for new pages, or with explicit placement, if a node has been
specified. Presently on UP NUMA this has the side-effect of preferring
node#0 allocations (since numa_node_id() == 0, though this could be
reworked if we could hand off a pfn to determine node placement), so
single-CPU NUMA systems will want to place smaller nodes further out in
terms of node id. Once a page has been bound to a node (via explicit
node id typing), we only do block allocations from partial free pages
that have a matching node id in the page flags.

The current implementation does have some scalability problems, in that
all partial free pages are tracked in the global freelist (with
contention due to the single spinlock). However, these are things that
are being reworked for SMP scalability first, while things like per-node
freelists can easily be built on top of this sort of functionality once
it's been added.

More background can be found in:

http://marc.info/?l=linux-mm&m=118117916022379&w=2
http://marc.info/?l=linux-mm&m=118170446306199&w=2
http://marc.info/?l=linux-mm&m=118187859420048&w=2

and subsequent threads.

Acked-by: Christoph Lameter <clameter@sgi.com>
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

--

include/linux/slab.h | 126 +++++++++++++++++++++++------------------------
include/linux/slab_def.h | 4 +
include/linux/slob_def.h | 46 +++++++++++++++++
include/linux/slub_def.h | 6 +-
mm/slob.c | 72 ++++++++++++++++++++------
5 files changed, 172 insertions(+), 82 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index a015236..e0bedd0 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -44,7 +44,6 @@ struct kmem_cache *kmem_cache_create(const char *, size_t, size_t,
void (*)(void *, struct kmem_cache *, unsigned long));
void kmem_cache_destroy(struct kmem_cache *);
int kmem_cache_shrink(struct kmem_cache *);
-void *kmem_cache_alloc(struct kmem_cache *, gfp_t);
void *kmem_cache_zalloc(struct kmem_cache *, gfp_t);
void kmem_cache_free(struct kmem_cache *, void *);
unsigned int kmem_cache_size(struct kmem_cache *);
@@ -63,16 +62,6 @@ int kmem_ptr_validate(struct kmem_cache *cachep, const void *ptr);
sizeof(struct __struct), __alignof__(struct __struct),\
(__flags), NULL, NULL)

-#ifdef CONFIG_NUMA
-extern void *kmem_cache_alloc_node(struct kmem_cache *, gfp_t flags, int node);
-#else
-static inline void *kmem_cache_alloc_node(struct kmem_cache *cachep,
- gfp_t flags, int node)
-{
- return kmem_cache_alloc(cachep, flags);
-}
-#endif
-
/*
* The largest kmalloc size supported by the slab allocators is
* 32 megabyte (2^25) or the maximum allocatable page order if that is
@@ -91,7 +80,6 @@ static inline void *kmem_cache_alloc_node(struct kmem_cache *cachep,
/*
* Common kmalloc functions provided by all allocators
*/
-void *__kmalloc(size_t, gfp_t);
void *__kzalloc(size_t, gfp_t);
void * __must_check krealloc(const void *, size_t, gfp_t);
void kfree(const void *);
@@ -102,40 +90,6 @@ size_t ksize(const void *);
* @n: number of elements.
* @size: element size.
* @flags: the type of memory to allocate.
- */
-static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
-{
- if (n != 0 && size > ULONG_MAX / n)
- return NULL;
- return __kzalloc(n * size, flags);
-}
-
-/*
- * Allocator specific definitions. These are mainly used to establish optimized
- * ways to convert kmalloc() calls to kmem_cache_alloc() invocations by selecting
- * the appropriate general cache at compile time.
- */
-
-#if defined(CONFIG_SLAB) || defined(CONFIG_SLUB)
-#ifdef CONFIG_SLUB
-#include <linux/slub_def.h>
-#else
-#include <linux/slab_def.h>
-#endif /* !CONFIG_SLUB */
-#else
-
-/*
- * Fallback definitions for an allocator not wanting to provide
- * its own optimized kmalloc definitions (like SLOB).
- */
-
-/**
- * kmalloc - allocate memory
- * @size: how many bytes of memory are required.
- * @flags: the type of memory to allocate.
- *
- * kmalloc is the normal method of allocating memory
- * in the kernel.
*
* The @flags argument may be one of:
*
@@ -143,7 +97,7 @@ static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
*
* %GFP_KERNEL - Allocate normal kernel ram. May sleep.
*
- * %GFP_ATOMIC - Allocation will not sleep.
+ * %GFP_ATOMIC - Allocation will not sleep. May use emergency pools.
* For example, use this inside interrupt handlers.
*
* %GFP_HIGHUSER - Allocate pages from high memory.
@@ -152,18 +106,22 @@ static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
*
* %GFP_NOFS - Do not make any fs calls while trying to get memory.
*
+ * %GFP_NOWAIT - Allocation will not sleep.
+ *
+ * %GFP_THISNODE - Allocate node-local memory only.
+ *
+ * %GFP_DMA - Allocation suitable for DMA.
+ * Should only be used for kmalloc() caches. Otherwise, use a
+ * slab created with SLAB_DMA.
+ *
* Also it is possible to set different flags by OR'ing
* in one or more of the following additional @flags:
*
* %__GFP_COLD - Request cache-cold pages instead of
* trying to return cache-warm pages.
*
- * %__GFP_DMA - Request memory from the DMA-capable zone.
- *
* %__GFP_HIGH - This allocation has high priority and may use emergency pools.
*
- * %__GFP_HIGHMEM - Allocated memory may be from highmem.
- *
* %__GFP_NOFAIL - Indicate that this allocation is in no way allowed to fail
* (think twice before using).
*
@@ -173,24 +131,57 @@ static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
* %__GFP_NOWARN - If allocation fails, don't issue any warnings.
*
* %__GFP_REPEAT - If allocation fails initially, try once more before failing.
+ *
+ * There are other flags available as well, but these are not intended
+ * for general use, and so are not documented here. For a full list of
+ * potential flags, always refer to linux/gfp.h.
*/
-static inline void *kmalloc(size_t size, gfp_t flags)
+static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
{
- return __kmalloc(size, flags);
+ if (n != 0 && size > ULONG_MAX / n)
+ return NULL;
+ return __kzalloc(n * size, flags);
}

-/**
- * kzalloc - allocate memory. The memory is set to zero.
- * @size: how many bytes of memory are required.
- * @flags: the type of memory to allocate (see kmalloc).
+/*
+ * Allocator specific definitions. These are mainly used to establish optimized
+ * ways to convert kmalloc() calls to kmem_cache_alloc() invocations by
+ * selecting the appropriate general cache at compile time.
+ *
+ * Allocators must define at least:
+ *
+ * kmem_cache_alloc()
+ * __kmalloc()
+ * kmalloc()
+ * kzalloc()
+ *
+ * Those wishing to support NUMA must also define:
+ *
+ * kmem_cache_alloc_node()
+ * kmalloc_node()
+ *
+ * See each allocator definition file for additional comments and
+ * implementation notes.
*/
-static inline void *kzalloc(size_t size, gfp_t flags)
-{
- return __kzalloc(size, flags);
-}
+#ifdef CONFIG_SLUB
+#include <linux/slub_def.h>
+#elif defined(CONFIG_SLOB)
+#include <linux/slob_def.h>
+#else
+#include <linux/slab_def.h>
#endif

-#ifndef CONFIG_NUMA
+#if !defined(CONFIG_NUMA) && !defined(CONFIG_SLOB)
+/**
+ * kmalloc_node - allocate memory from a specific node
+ * @size: how many bytes of memory are required.
+ * @flags: the type of memory to allocate (see kcalloc).
+ * @node: node to allocate from.
+ *
+ * kmalloc() for non-local nodes, used to allocate from a specific node
+ * if available. Equivalent to kmalloc() in the non-NUMA single-node
+ * case.
+ */
static inline void *kmalloc_node(size_t size, gfp_t flags, int node)
{
return kmalloc(size, flags);
@@ -200,7 +191,15 @@ static inline void *__kmalloc_node(size_t size, gfp_t flags, int node)
{
return __kmalloc(size, flags);
}
-#endif /* !CONFIG_NUMA */
+
+void *kmem_cache_alloc(struct kmem_cache *, gfp_t);
+
+static inline void *kmem_cache_alloc_node(struct kmem_cache *cachep,
+ gfp_t flags, int node)
+{
+ return kmem_cache_alloc(cachep, flags);
+}
+#endif /* !CONFIG_NUMA && !CONFIG_SLOB */

/*
* kmalloc_track_caller is a special version of kmalloc that records the
@@ -247,4 +246,3 @@ extern void *__kmalloc_node_track_caller(size_t, gfp_t, int, void *);

#endif /* __KERNEL__ */
#endif /* _LINUX_SLAB_H */
-
diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h
index 8d81a60..365d036 100644
--- a/include/linux/slab_def.h
+++ b/include/linux/slab_def.h
@@ -25,6 +25,9 @@ struct cache_sizes {
};
extern struct cache_sizes malloc_sizes[];

+void *kmem_cache_alloc(struct kmem_cache *, gfp_t);
+void *__kmalloc(size_t size, gfp_t flags);
+
static inline void *kmalloc(size_t size, gfp_t flags)
{
if (__builtin_constant_p(size)) {
@@ -79,6 +82,7 @@ found:

#ifdef CONFIG_NUMA
extern void *__kmalloc_node(size_t size, gfp_t flags, int node);
+extern void *kmem_cache_alloc_node(struct kmem_cache *, gfp_t flags, int node);

static inline void *kmalloc_node(size_t size, gfp_t flags, int node)
{
diff --git a/include/linux/slob_def.h b/include/linux/slob_def.h
new file mode 100644
index 0000000..a2daf2d
--- /dev/null
+++ b/include/linux/slob_def.h
@@ -0,0 +1,46 @@
+#ifndef __LINUX_SLOB_DEF_H
+#define __LINUX_SLOB_DEF_H
+
+void *kmem_cache_alloc_node(struct kmem_cache *, gfp_t flags, int node);
+
+static inline void *kmem_cache_alloc(struct kmem_cache *cachep, gfp_t flags)
+{
+ return kmem_cache_alloc_node(cachep, flags, -1);
+}
+
+void *__kmalloc_node(size_t size, gfp_t flags, int node);
+
+static inline void *kmalloc_node(size_t size, gfp_t flags, int node)
+{
+ return __kmalloc_node(size, flags, node);
+}
+
+/**
+ * kmalloc - allocate memory
+ * @size: how many bytes of memory are required.
+ * @flags: the type of memory to allocate (see kcalloc).
+ *
+ * kmalloc is the normal method of allocating memory
+ * in the kernel.
+ */
+static inline void *kmalloc(size_t size, gfp_t flags)
+{
+ return __kmalloc_node(size, flags, -1);
+}
+
+static inline void *__kmalloc(size_t size, gfp_t flags)
+{
+ return kmalloc(size, flags);
+}
+
+/**
+ * kzalloc - allocate memory. The memory is set to zero.
+ * @size: how many bytes of memory are required.
+ * @flags: the type of memory to allocate (see kcalloc).
+ */
+static inline void *kzalloc(size_t size, gfp_t flags)
+{
+ return __kzalloc(size, flags);
+}
+
+#endif /* __LINUX_SLOB_DEF_H */
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 0764c82..5b68505 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -153,6 +153,9 @@ static inline struct kmem_cache *kmalloc_slab(size_t size)
#define SLUB_DMA 0
#endif

+void *kmem_cache_alloc(struct kmem_cache *, gfp_t);
+void *__kmalloc(size_t size, gfp_t flags);
+
static inline void *kmalloc(size_t size, gfp_t flags)
{
if (__builtin_constant_p(size) && !(flags & SLUB_DMA)) {
@@ -180,7 +183,8 @@ static inline void *kzalloc(size_t size, gfp_t flags)
}

#ifdef CONFIG_NUMA
-extern void *__kmalloc_node(size_t size, gfp_t flags, int node);
+void *__kmalloc_node(size_t size, gfp_t flags, int node);
+void *kmem_cache_alloc_node(struct kmem_cache *, gfp_t flags, int node);

static inline void *kmalloc_node(size_t size, gfp_t flags, int node)
{
diff --git a/mm/slob.c b/mm/slob.c
index 06e5e72..b99b0ef 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -3,6 +3,8 @@
*
* Matt Mackall <mpm@selenic.com> 12/30/03
*
+ * NUMA support by Paul Mundt, 2007.
+ *
* How SLOB works:
*
* The core of SLOB is a traditional K&R style heap allocator, with
@@ -10,7 +12,7 @@
* allocator is as little as 2 bytes, however typically most architectures
* will require 4 bytes on 32-bit and 8 bytes on 64-bit.
*
- * The slob heap is a linked list of pages from __get_free_page, and
+ * The slob heap is a linked list of pages from alloc_pages(), and
* within each page, there is a singly-linked list of free blocks (slob_t).
* The heap is grown on demand and allocation from the heap is currently
* first-fit.
@@ -18,7 +20,7 @@
* Above this is an implementation of kmalloc/kfree. Blocks returned
* from kmalloc are prepended with a 4-byte header with the kmalloc size.
* If kmalloc is asked for objects of PAGE_SIZE or larger, it calls
- * __get_free_pages directly, allocating compound pages so the page order
+ * alloc_pages() directly, allocating compound pages so the page order
* does not have to be separately tracked, and also stores the exact
* allocation size in page->private so that it can be used to accurately
* provide ksize(). These objects are detected in kfree() because slob_page()
@@ -29,10 +31,23 @@
* 4-byte alignment unless the SLAB_HWCACHE_ALIGN flag is set, in which
* case the low-level allocator will fragment blocks to create the proper
* alignment. Again, objects of page-size or greater are allocated by
- * calling __get_free_pages. As SLAB objects know their size, no separate
+ * calling alloc_pages(). As SLAB objects know their size, no separate
* size bookkeeping is necessary and there is essentially no allocation
* space overhead, and compound pages aren't needed for multi-page
* allocations.
+ *
+ * NUMA support in SLOB is fairly simplistic, pushing most of the real
+ * logic down to the page allocator, and simply doing the node accounting
+ * on the upper levels. In the event that a node id is explicitly
+ * provided, alloc_pages_node() with the specified node id is used
+ * instead. The common case (or when the node id isn't explicitly provided)
+ * will default to the current node, as per numa_node_id().
+ *
+ * Node aware pages are still inserted in to the global freelist, and
+ * these are scanned for by matching against the node id encoded in the
+ * page flags. As a result, block allocations that can be satisfied from
+ * the freelist will only be done so on pages residing on the same node,
+ * in order to prevent random node placement.
*/

#include <linux/kernel.h>
@@ -204,6 +219,23 @@ static int slob_last(slob_t *s)
return !((unsigned long)slob_next(s) & ~PAGE_MASK);
}

+static void *slob_new_page(gfp_t gfp, int order, int node)
+{
+ void *page;
+
+#ifdef CONFIG_NUMA
+ if (node != -1)
+ page = alloc_pages_node(node, gfp, order);
+ else
+#endif
+ page = alloc_pages(gfp, order);
+
+ if (!page)
+ return NULL;
+
+ return page_address(page);
+}
+
/*
* Allocate a slob block within a given slob_page sp.
*/
@@ -258,7 +290,7 @@ static void *slob_page_alloc(struct slob_page *sp, size_t size, int align)
/*
* slob_alloc: entry point into the slob allocator.
*/
-static void *slob_alloc(size_t size, gfp_t gfp, int align)
+static void *slob_alloc(size_t size, gfp_t gfp, int align, int node)
{
struct slob_page *sp;
slob_t *b = NULL;
@@ -267,6 +299,15 @@ static void *slob_alloc(size_t size, gfp_t gfp, int align)
spin_lock_irqsave(&slob_lock, flags);
/* Iterate through each partially free page, try to find room */
list_for_each_entry(sp, &free_slob_pages, list) {
+#ifdef CONFIG_NUMA
+ /*
+ * If there's a node specification, search for a partial
+ * page with a matching node id in the freelist.
+ */
+ if (node != -1 && page_to_nid(&sp->page) != node)
+ continue;
+#endif
+
if (sp->units >= SLOB_UNITS(size)) {
b = slob_page_alloc(sp, size, align);
if (b)
@@ -277,7 +318,7 @@ static void *slob_alloc(size_t size, gfp_t gfp, int align)

/* Not enough space: must allocate a new page */
if (!b) {
- b = (slob_t *)__get_free_page(gfp);
+ b = slob_new_page(gfp, 0, node);
if (!b)
return 0;
sp = (struct slob_page *)virt_to_page(b);
@@ -381,22 +422,20 @@ out:
#define ARCH_SLAB_MINALIGN __alignof__(unsigned long)
#endif

-
-void *__kmalloc(size_t size, gfp_t gfp)
+void *__kmalloc_node(size_t size, gfp_t gfp, int node)
{
int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);

if (size < PAGE_SIZE - align) {
unsigned int *m;
- m = slob_alloc(size + align, gfp, align);
+ m = slob_alloc(size + align, gfp, align, node);
if (m)
*m = size;
return (void *)m + align;
} else {
void *ret;

- ret = (void *) __get_free_pages(gfp | __GFP_COMP,
- get_order(size));
+ ret = slob_new_page(gfp | __GFP_COMP, get_order(size), node);
if (ret) {
struct page *page;
page = virt_to_page(ret);
@@ -405,7 +444,7 @@ void *__kmalloc(size_t size, gfp_t gfp)
return ret;
}
}
-EXPORT_SYMBOL(__kmalloc);
+EXPORT_SYMBOL(__kmalloc_node);

/**
* krealloc - reallocate memory. The contents will remain unchanged.
@@ -455,7 +494,6 @@ void kfree(const void *block)
} else
put_page(&sp->page);
}
-
EXPORT_SYMBOL(kfree);

/* can't use ksize for kmem_cache_alloc memory, only kmalloc */
@@ -487,7 +525,7 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size,
{
struct kmem_cache *c;

- c = slob_alloc(sizeof(struct kmem_cache), flags, 0);
+ c = slob_alloc(sizeof(struct kmem_cache), flags, 0, -1);

if (c) {
c->name = name;
@@ -517,21 +555,21 @@ void kmem_cache_destroy(struct kmem_cache *c)
}
EXPORT_SYMBOL(kmem_cache_destroy);

-void *kmem_cache_alloc(struct kmem_cache *c, gfp_t flags)
+void *kmem_cache_alloc_node(struct kmem_cache *c, gfp_t flags, int node)
{
void *b;

if (c->size < PAGE_SIZE)
- b = slob_alloc(c->size, flags, c->align);
+ b = slob_alloc(c->size, flags, c->align, node);
else
- b = (void *)__get_free_pages(flags, get_order(c->size));
+ b = slob_new_page(flags, get_order(c->size), node);

if (c->ctor)
c->ctor(b, c, 0);

return b;
}
-EXPORT_SYMBOL(kmem_cache_alloc);
+EXPORT_SYMBOL(kmem_cache_alloc_node);

void *kmem_cache_zalloc(struct kmem_cache *c, gfp_t flags)
{