[PATCH 2/2] slub: name kmalloc slabs at creation time

[PATCH 2/2] slub: name kmalloc slabs at creation time

[Iliyan Malchev]

During slub's initialization, most kmalloc slabs are named "kmalloc" at
creation time, and later, once slub is fully initialized, get renamed to
kmalloc-<size>.  The trouble is that slab names passed to option slub_debug
will not get recognized, because they will all be called "kmalloc" at the time
the command-line option is being processed.

This patch reserves a small static array to hold the names of the kmalloc
slabs, and uses a small helper function __uitoa (unsigned integer to ascii) to
format names as appropriately.

Signed-off-by: Iliyan Malchev <malchev@google.com>
---
 mm/slub.c |   35 +++++++++++++++++++++++++++--------
 1 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 8e7a282..a4d02cf 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3070,6 +3070,11 @@ static struct kmem_cache *kmem_cache;
 static struct kmem_cache *kmalloc_dma_caches[SLUB_PAGE_SHIFT];
 #endif
 
+#define KMALLOC_NAME_SUFFIX_MAX	8
+#define KMALLOC_NAME_MAX	(strlen("kmalloc-") + KMALLOC_NAME_SUFFIX_MAX)
+#define KMALLOC_CACHE_NAME_LEN	(SLUB_PAGE_SHIFT - KMALLOC_SHIFT_LOW)
+static char kmalloc_cache_names[KMALLOC_CACHE_NAME_LEN * KMALLOC_NAME_MAX];
+
 static int __init setup_slub_min_order(char *str)
 {
 	get_option(&str, &slub_min_order);
@@ -3544,6 +3549,19 @@ static void __init kmem_cache_bootstrap_fixup(struct kmem_cache *s)
 	}
 }
 
+/* Convert a positive integer to its decimal string representation, starting at
+ * the end of the buffer and going backwards, not exceeding maxlen characters.
+ */
+static __init char *__pos_int_to_string(unsigned int value, char* string,
+					int maxindex, int maxlen)
+{
+	int i = maxindex - 1;
+	string[maxindex] = 0;
+	for (; value && i && maxlen; i--, maxlen--, value /= 10)
+		string[i] = '0' + (value % 10);
+	return string + i + 1;
+}
+
 void __init kmem_cache_init(void)
 {
 	int i;
@@ -3552,6 +3570,7 @@ void __init kmem_cache_init(void)
 	int order;
 	struct kmem_cache *temp_kmem_cache_node;
 	unsigned long kmalloc_size;
+	char *name_start;
 
 	kmem_size = offsetof(struct kmem_cache, node) +
 				nr_node_ids * sizeof(struct kmem_cache_node *);
@@ -3652,8 +3671,15 @@ void __init kmem_cache_init(void)
 		caches++;
 	}
 
+	name_start = kmalloc_cache_names;
 	for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++) {
-		kmalloc_caches[i] = create_kmalloc_cache("kmalloc", 1 << i, 0);
+		char *name = __pos_int_to_string(1 << i, name_start,
+					KMALLOC_NAME_MAX - 1,
+					KMALLOC_NAME_SUFFIX_MAX);
+		name -= 8;
+		strncpy(name, "kmalloc-", 8);
+		name_start += KMALLOC_NAME_MAX;
+		kmalloc_caches[i] = create_kmalloc_cache(name, 1 << i, 0);
 		caches++;
 	}
 
@@ -3670,13 +3696,6 @@ void __init kmem_cache_init(void)
 		BUG_ON(!kmalloc_caches[2]->name);
 	}
 
-	for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++) {
-		char *s = kasprintf(GFP_NOWAIT, "kmalloc-%d", 1 << i);
-
-		BUG_ON(!s);
-		kmalloc_caches[i]->name = s;
-	}
-
 #ifdef CONFIG_SMP
 	register_cpu_notifier(&slab_notifier);
 #endif
-- 
1.7.3.1

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Re: [PATCH 2/2] slub: name kmalloc slabs at creation time

[Christoph Lameter]

On Mon, 8 Aug 2011, Iliyan Malchev wrote:

> This patch reserves a small static array to hold the names of the kmalloc
> slabs, and uses a small helper function __uitoa (unsigned integer to ascii) to
> format names as appropriately

simple_strtoull etc is not satisfactory?

> +/* Convert a positive integer to its decimal string representation, starting at
> + * the end of the buffer and going backwards, not exceeding maxlen characters.
> + */
> +static __init char *__pos_int_to_string(unsigned int value, char* string,
> +					int maxindex, int maxlen)
> +{
> +	int i = maxindex - 1;
> +	string[maxindex] = 0;
> +	for (; value && i && maxlen; i--, maxlen--, value /= 10)
> +		string[i] = '0' + (value % 10);
> +	return string + i + 1;
> +}

Please use the standard string operations of the kernel.

> @@ -3652,8 +3671,15 @@ void __init kmem_cache_init(void)
>  		caches++;
>  	}
>
> +	name_start = kmalloc_cache_names;
>  	for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++) {
> -		kmalloc_caches[i] = create_kmalloc_cache("kmalloc", 1 << i, 0);
> +		char *name = __pos_int_to_string(1 << i, name_start,
> +					KMALLOC_NAME_MAX - 1,
> +					KMALLOC_NAME_SUFFIX_MAX);
> +		name -= 8;

8 is what? The length of "kmalloc-" right?

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