2007-02-22 12:40:25

by Pekka Enberg

Subject: [PATCH 1/2] slab: introduce krealloc

From: Pekka Enberg <[email protected]>

This introduce krealloc() that reallocates memory while keeping the
contents unchanged. The allocator avoids reallocation if the new size
fits the currently used cache. I also added a simple non-optimized
version for mm/slob.c for compatibility.

Cc: Josef Sipek <[email protected]>
Cc: Matt Mackall <[email protected]>
Cc: Christoph Lameter <[email protected]>
Signed-off-by: Pekka Enberg <[email protected]>
---
include/linux/slab.h | 1 +
mm/slab.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
mm/slob.c | 33 +++++++++++++++++++++++++++++++++
3 files changed, 81 insertions(+)

Index: 2.6/include/linux/slab.h
===================================================================
--- 2.6.orig/include/linux/slab.h 2007-02-22 11:33:15.000000000 +0200
+++ 2.6/include/linux/slab.h 2007-02-22 11:33:39.000000000 +0200
@@ -72,6 +72,7 @@
*/
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 *);
unsigned int ksize(const void *);

Index: 2.6/mm/slab.c
===================================================================
--- 2.6.orig/mm/slab.c 2007-02-22 11:33:15.000000000 +0200
+++ 2.6/mm/slab.c 2007-02-22 11:33:28.000000000 +0200
@@ -3737,6 +3737,53 @@
#endif

/**
+ * krealloc - reallocate memory. The contents will remain unchanged.
+ *
+ * @p: object to reallocate memory for.
+ * @new_size: how many bytes of memory are required.
+ * @flags: the type of memory to allocate.
+ *
+ * The contents of the object pointed to are preserved up to the
+ * lesser of the new and old sizes. If @p is %NULL, krealloc()
+ * behaves exactly like kmalloc(). If @size is 0 and @p is not a
+ * %NULL pointer, the object pointed to is freed.
+ */
+void *krealloc(const void *p, size_t new_size, gfp_t flags)
+{
+ struct kmem_cache *cache, *new_cache;
+ void *ret;
+
+ if (unlikely(!p))
+ return kmalloc_track_caller(new_size, flags);
+
+ if (unlikely(!new_size)) {
+ kfree(p);
+ return NULL;
+ }
+
+ cache = virt_to_cache(p);
+ new_cache = __find_general_cachep(new_size, flags);
+
+ /*
+ * If new size fits in the current cache, bail out.
+ */
+ if (likely(cache == new_cache))
+ return (void *)p;
+
+ /*
+ * We are on the slow-path here so do not use __cache_alloc
+ * because it bloats kernel text.
+ */
+ ret = kmalloc_track_caller(new_size, flags);
+ if (ret) {
+ memcpy(ret, p, min(new_size, ksize(p)));
+ kfree(p);
+ }
+ return ret;
+}
+EXPORT_SYMBOL(krealloc);
+
+/**
* kmem_cache_free - Deallocate an object
* @cachep: The cache the allocation was from.
* @objp: The previously allocated object.
Index: 2.6/mm/slob.c
===================================================================
--- 2.6.orig/mm/slob.c 2007-02-22 11:33:15.000000000 +0200
+++ 2.6/mm/slob.c 2007-02-22 11:33:28.000000000 +0200
@@ -190,6 +190,39 @@
}
EXPORT_SYMBOL(__kmalloc);

+/**
+ * krealloc - reallocate memory. The contents will remain unchanged.
+ *
+ * @p: object to reallocate memory for.
+ * @new_size: how many bytes of memory are required.
+ * @flags: the type of memory to allocate.
+ *
+ * The contents of the object pointed to are preserved up to the
+ * lesser of the new and old sizes. If @p is %NULL, krealloc()
+ * behaves exactly like kmalloc(). If @size is 0 and @p is not a
+ * %NULL pointer, the object pointed to is freed.
+ */
+void *krealloc(const void *p, size_t new_size, gfp_t flags)
+{
+ void *ret;
+
+ if (unlikely(!p))
+ return kmalloc_track_caller(new_size, flags);
+
+ if (unlikely(!new_size)) {
+ kfree(p);
+ return NULL;
+ }
+
+ ret = kmalloc_track_caller(new_size, flags);
+ if (ret) {
+ memcpy(ret, p, min(new_size, ksize(p)));
+ kfree(p);
+ }
+ return ret;
+}
+EXPORT_SYMBOL(krealloc);
+
void kfree(const void *block)
{
bigblock_t *bb, **last = &bigblocks;

2007-02-22 15:20:09

by Christoph Lameter

Subject: Re: [PATCH 1/2] slab: introduce krealloc

On Thu, 22 Feb 2007, Pekka J Enberg wrote:

> This introduce krealloc() that reallocates memory while keeping the
> contents unchanged. The allocator avoids reallocation if the new size
> fits the currently used cache. I also added a simple non-optimized
> version for mm/slob.c for compatibility.

Acked-by: Christoph Lameter <[email protected]>

2007-02-22 15:34:19

by Matt Mackall

Subject: Re: [PATCH 1/2] slab: introduce krealloc

On Thu, Feb 22, 2007 at 02:40:22PM +0200, Pekka J Enberg wrote:
> From: Pekka Enberg <[email protected]>
>
> This introduce krealloc() that reallocates memory while keeping the
> contents unchanged. The allocator avoids reallocation if the new size
> fits the currently used cache. I also added a simple non-optimized
> version for mm/slob.c for compatibility.
>
> Cc: Josef Sipek <[email protected]>
> Cc: Matt Mackall <[email protected]>
> Cc: Christoph Lameter <[email protected]>
> Signed-off-by: Pekka Enberg <[email protected]>

Acked-by: Matt Mackall <[email protected]>

--
Mathematics is the supreme nostalgia of our time.

2007-02-22 18:19:26

by Josef Sipek

Subject: Re: [PATCH 1/2] slab: introduce krealloc

On Thu, Feb 22, 2007 at 02:40:22PM +0200, Pekka J Enberg wrote:
> From: Pekka Enberg <[email protected]>
>
> This introduce krealloc() that reallocates memory while keeping the
> contents unchanged. The allocator avoids reallocation if the new size
> fits the currently used cache. I also added a simple non-optimized
> version for mm/slob.c for compatibility.

Acked-by: Josef 'Jeff' Sipek <[email protected]>