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Subject[PATCH -mmotm 06/30] mm: kmem_alloc_estimate()
From 4a2dff5cf02e9d7f6ee9345c337697c4ab66c6dc Mon Sep 17 00:00:00 2001
From: Xiaotian Feng <dfeng@redhat.com>
Date: Tue, 13 Jul 2010 10:41:22 +0800
Subject: [PATCH 06/30] mm: kmem_alloc_estimate()

Provide a method to get the upper bound on the pages needed to allocate
a given number of objects from a given kmem_cache.

This lays the foundation for a generic reserve framework as presented in
a later patch in this series. This framework needs to convert object demand
(kmalloc() bytes, kmem_cache_alloc() objects) to pages.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Xiaotian Feng <dfeng@redhat.com>
---
include/linux/slab.h | 4 ++
mm/slab.c | 75 +++++++++++++++++++++++++++++++++++++++++++
mm/slob.c | 67 ++++++++++++++++++++++++++++++++++++++
mm/slub.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 233 insertions(+), 0 deletions(-)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 49d1247..b57b9ca 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -108,6 +108,8 @@ unsigned int kmem_cache_size(struct kmem_cache *);
const char *kmem_cache_name(struct kmem_cache *);
int kern_ptr_validate(const void *ptr, unsigned long size);
int kmem_ptr_validate(struct kmem_cache *cachep, const void *ptr);
+unsigned kmem_alloc_estimate(struct kmem_cache *cachep,
+ gfp_t flags, int objects);

/*
* Please use this macro to create slab caches. Simply specify the
@@ -144,6 +146,8 @@ void * __must_check krealloc(const void *, size_t, gfp_t);
void kfree(const void *);
void kzfree(const void *);
size_t ksize(const void *);
+unsigned kmalloc_estimate_objs(size_t, gfp_t, int);
+unsigned kmalloc_estimate_bytes(gfp_t, size_t);

/*
* Allocator specific definitions. These are mainly used to establish optimized
diff --git a/mm/slab.c b/mm/slab.c
index d8cd757..2a0dd0d 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3913,6 +3913,81 @@ const char *kmem_cache_name(struct kmem_cache *cachep)
EXPORT_SYMBOL_GPL(kmem_cache_name);

/*
+ * Calculate the upper bound of pages required to sequentially allocate
+ * @objects objects from @cachep.
+ */
+unsigned kmem_alloc_estimate(struct kmem_cache *cachep,
+ gfp_t flags, int objects)
+{
+ /*
+ * (1) memory for objects,
+ */
+ unsigned nr_slabs = DIV_ROUND_UP(objects, cachep->num);
+ unsigned nr_pages = nr_slabs << cachep->gfporder;
+
+ /*
+ * (2) memory for each per-cpu queue (nr_cpu_ids),
+ * (3) memory for each per-node alien queues (nr_cpu_ids), and
+ * (4) some amount of memory for the slab management structures
+ *
+ * XXX: truely account these
+ */
+ nr_pages += 1 + ilog2(nr_pages);
+
+ return nr_pages;
+}
+
+/*
+ * Calculate the upper bound of pages required to sequentially allocate
+ * @count objects of @size bytes from kmalloc given @flags.
+ */
+unsigned kmalloc_estimate_objs(size_t size, gfp_t flags, int count)
+{
+ struct kmem_cache *s = kmem_find_general_cachep(size, flags);
+ if (!s)
+ return 0;
+
+ return kmem_alloc_estimate(s, flags, count);
+}
+EXPORT_SYMBOL_GPL(kmalloc_estimate_objs);
+
+/*
+ * Calculate the upper bound of pages requires to sequentially allocate @bytes
+ * from kmalloc in an unspecified number of allocations of nonuniform size.
+ */
+unsigned kmalloc_estimate_bytes(gfp_t flags, size_t bytes)
+{
+ unsigned long pages;
+ struct cache_sizes *csizep = malloc_sizes;
+
+ /*
+ * multiply by two, in order to account the worst case slack space
+ * due to the power-of-two allocation sizes.
+ */
+ pages = DIV_ROUND_UP(2 * bytes, PAGE_SIZE);
+
+ /*
+ * add the kmem_cache overhead of each possible kmalloc cache
+ */
+ for (csizep = malloc_sizes; csizep->cs_cachep; csizep++) {
+ struct kmem_cache *s;
+
+#ifdef CONFIG_ZONE_DMA
+ if (unlikely(flags & __GFP_DMA))
+ s = csizep->cs_dmacachep;
+ else
+#endif
+ s = csizep->cs_cachep;
+
+ if (s)
+ pages += kmem_alloc_estimate(s, flags, 0);
+ }
+
+ return pages;
+}
+EXPORT_SYMBOL_GPL(kmalloc_estimate_bytes);
+
+/*
* This initializes kmem_list3 or resizes various caches for all nodes.
*/
static int alloc_kmemlist(struct kmem_cache *cachep, gfp_t gfp)
diff --git a/mm/slob.c b/mm/slob.c
index b84b611..0caf938 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -695,6 +695,73 @@ int slab_is_available(void)
return slob_ready;
}

+static __slob_estimate(unsigned size, unsigned align, unsigned objects)
+{
+ unsigned nr_pages;
+
+ size = SLOB_UNIT * SLOB_UNITS(size + align - 1);
+
+ if (size <= PAGE_SIZE) {
+ nr_pages = DIV_ROUND_UP(objects, PAGE_SIZE / size);
+ } else {
+ nr_pages = objects << get_order(size);
+ }
+
+ return nr_pages;
+}
+
+/*
+ * Calculate the upper bound of pages required to sequentially allocate
+ * @objects objects from @cachep.
+ */
+unsigned kmem_alloc_estimate(struct kmem_cache *c, gfp_t flags, int objects)
+{
+ unsigned size = c->size;
+
+ if (c->flags & SLAB_DESTROY_BY_RCU)
+ size += sizeof(struct slob_rcu);
+
+ return __slob_estimate(size, c->align, objects);
+}
+
+/*
+ * Calculate the upper bound of pages required to sequentially allocate
+ * @count objects of @size bytes from kmalloc given @flags.
+ */
+unsigned kmalloc_estimate_objs(size_t size, gfp_t flags, int count)
+{
+ unsigned align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
+
+ return __slob_estimate(size, align, count);
+}
+EXPORT_SYMBOL_GPL(kmalloc_estimate_objs);
+
+/*
+ * Calculate the upper bound of pages requires to sequentially allocate @bytes
+ * from kmalloc in an unspecified number of allocations of nonuniform size.
+ */
+unsigned kmalloc_estimate_bytes(gfp_t flags, size_t bytes)
+{
+ unsigned long pages;
+
+ /*
+ * Multiply by two, in order to account the worst case slack space
+ * due to the power-of-two allocation sizes.
+ *
+ * While not true for slob, it cannot do worse than that for sequential
+ * allocations.
+ */
+ pages = DIV_ROUND_UP(2 * bytes, PAGE_SIZE);
+
+ /*
+ * Our power of two series starts at PAGE_SIZE, so add one page.
+ */
+ pages++;
+
+ return pages;
+}
+EXPORT_SYMBOL_GPL(kmalloc_estimate_bytes);
+
void __init kmem_cache_init(void)
{
slob_ready = 1;
diff --git a/mm/slub.c b/mm/slub.c
index 7a5d6dc..056545e 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2435,6 +2435,42 @@ const char *kmem_cache_name(struct kmem_cache *s)
}
EXPORT_SYMBOL(kmem_cache_name);

+/*
+ * Calculate the upper bound of pages required to sequentially allocate
+ * @objects objects from @cachep.
+ *
+ * We should use s->min_objects because those are the least efficient.
+ */
+unsigned kmem_alloc_estimate(struct kmem_cache *s, gfp_t flags, int objects)
+{
+ unsigned long pages;
+ struct kmem_cache_order_objects x;
+
+ if (WARN_ON(!s) || WARN_ON(!oo_objects(s->min)))
+ return 0;
+
+ x = s->min;
+ pages = DIV_ROUND_UP(objects, oo_objects(x)) << oo_order(x);
+
+ /*
+ * Account the possible additional overhead if the slab holds more that
+ * one object. Use s->max_objects because that's the worst case.
+ */
+ x = s->oo;
+ if (oo_objects(x) > 1) {
+ /*
+ * Account the possible additional overhead if per cpu slabs
+ * are currently empty and have to be allocated. This is very
+ * unlikely but a possible scenario immediately after
+ * kmem_cache_shrink.
+ */
+ pages += num_possible_cpus() << oo_order(x);
+ }
+
+ return pages;
+}
+EXPORT_SYMBOL_GPL(kmem_alloc_estimate);
+
static void list_slab_objects(struct kmem_cache *s, struct page *page,
const char *text)
{
@@ -2868,6 +2904,57 @@ void kfree(const void *x)
EXPORT_SYMBOL(kfree);

/*
+ * Calculate the upper bound of pages required to sequentially allocate
+ * @count objects of @size bytes from kmalloc given @flags.
+ */
+unsigned kmalloc_estimate_objs(size_t size, gfp_t flags, int count)
+{
+ struct kmem_cache *s = get_slab(size, flags);
+ if (!s)
+ return 0;
+
+ return kmem_alloc_estimate(s, flags, count);
+
+}
+EXPORT_SYMBOL_GPL(kmalloc_estimate_objs);
+
+/*
+ * Calculate the upper bound of pages requires to sequentially allocate @bytes
+ * from kmalloc in an unspecified number of allocations of nonuniform size.
+ */
+unsigned kmalloc_estimate_bytes(gfp_t flags, size_t bytes)
+{
+ int i;
+ unsigned long pages;
+
+ /*
+ * multiply by two, in order to account the worst case slack space
+ * due to the power-of-two allocation sizes.
+ */
+ pages = DIV_ROUND_UP(2 * bytes, PAGE_SIZE);
+
+ /*
+ * add the kmem_cache overhead of each possible kmalloc cache
+ */
+ for (i = 1; i < PAGE_SHIFT; i++) {
+ struct kmem_cache *s;
+
+#ifdef CONFIG_ZONE_DMA
+ if (unlikely(flags & SLUB_DMA))
+ s = dma_kmalloc_cache(i, flags);
+ else
+#endif
+ s = &kmalloc_caches[i];
+
+ if (s)
+ pages += kmem_alloc_estimate(s, flags, 0);
+ }
+
+ return pages;
+}
+EXPORT_SYMBOL_GPL(kmalloc_estimate_bytes);
+
+/*
* kmem_cache_shrink removes empty slabs from the partial lists and sorts
* the remaining slabs by the number of items in use. The slabs with the
* most items in use come first. New allocations will then fill those up
--
1.7.1.1


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