Andrew> It hardly seems worth it, really. Better savings would
Andrew> come from doing the same trick to kmem_cache_alloc() then
Andrew> tweaking kmalloc().
Yep, right as usual; here's an updated patch. Do with it as you will --
I won't be hurt if you dump it, since I had fun trying this out.
Reduce kernel text by moving many uses of GFP_KERNEL out of line, by
creating __kmem_cache_alloc_gfp_kernel(), __kmalloc_gfp_kernel() and
__kzalloc_gfp_kernel() wrapper functions. Then kmem_cache_alloc(),
kmalloc() and kzalloc() can be inline functions that just call their
_gfp_kernel version if their flags parameter is a compile-time
constant and is GFP_KERNEL, and call their ordinary version otherwise.
On an x86_64 allyesconfig kernel, I see the following sizes:
text data bss dec hex filename
24202272 7609162 1998512 33809946 203e61a vmlinux-before
24197561 7609474 1998512 33805547 203d4eb vmlinux-after
for a net savings of 4711 bytes of text (at a cost of 312 bytes of
data for some reason). With my usual config, the patched kernel boots
and runs fine.
Signed-off-by: Roland Dreier <[email protected]>
diff --git a/include/linux/slab.h b/include/linux/slab.h
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -61,7 +61,8 @@ extern kmem_cache_t *kmem_cache_create(c
void (*)(void *, kmem_cache_t *, unsigned long));
extern int kmem_cache_destroy(kmem_cache_t *);
extern int kmem_cache_shrink(kmem_cache_t *);
-extern void *kmem_cache_alloc(kmem_cache_t *, unsigned int __nocast);
+extern void *__kmem_cache_alloc(kmem_cache_t *, unsigned int __nocast);
+extern void *__kmem_cache_alloc_gfp_kernel(kmem_cache_t *);
extern void kmem_cache_free(kmem_cache_t *, void *);
extern unsigned int kmem_cache_size(kmem_cache_t *);
extern const char *kmem_cache_name(kmem_cache_t *);
@@ -75,6 +76,15 @@ struct cache_sizes {
};
extern struct cache_sizes malloc_sizes[];
extern void *__kmalloc(size_t, unsigned int __nocast);
+extern void *__kmalloc_gfp_kernel(size_t);
+
+static inline void *kmem_cache_alloc(kmem_cache_t *cache, unsigned int __nocast flags)
+{
+ if (__builtin_constant_p(flags) && flags == GFP_KERNEL)
+ return __kmem_cache_alloc_gfp_kernel(cache);
+
+ return __kmem_cache_alloc(cache, flags);
+}
static inline void *kmalloc(size_t size, unsigned int __nocast flags)
{
@@ -96,10 +106,22 @@ found:
malloc_sizes[i].cs_dmacachep :
malloc_sizes[i].cs_cachep, flags);
}
+
+ if (__builtin_constant_p(flags) && flags == GFP_KERNEL)
+ return __kmalloc_gfp_kernel(size);
return __kmalloc(size, flags);
}
-extern void *kzalloc(size_t, unsigned int __nocast);
+extern void *__kzalloc(size_t, unsigned int __nocast);
+extern void *__kzalloc_gfp_kernel(size_t);
+
+static inline void *kzalloc(size_t size, unsigned int __nocast flags)
+{
+ if (__builtin_constant_p(flags) && flags == GFP_KERNEL)
+ return __kzalloc_gfp_kernel(size);
+
+ return __kzalloc(size, flags);
+}
/**
* kcalloc - allocate memory for an array. The memory is set to zero.
diff --git a/mm/slab.c b/mm/slab.c
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2778,11 +2778,17 @@ static inline void __cache_free(kmem_cac
* Allocate an object from this cache. The flags are only relevant
* if the cache has no available objects.
*/
-void *kmem_cache_alloc(kmem_cache_t *cachep, unsigned int __nocast flags)
+void *__kmem_cache_alloc(kmem_cache_t *cachep, unsigned int __nocast flags)
{
return __cache_alloc(cachep, flags);
}
-EXPORT_SYMBOL(kmem_cache_alloc);
+EXPORT_SYMBOL(__kmem_cache_alloc);
+
+void *__kmem_cache_alloc_gfp_kernel(kmem_cache_t *cachep)
+{
+ return __cache_alloc(cachep, GFP_KERNEL);
+}
+EXPORT_SYMBOL(__kmem_cache_alloc_gfp_kernel);
/**
* kmem_ptr_validate - check if an untrusted pointer might
@@ -2912,6 +2918,12 @@ void *__kmalloc(size_t size, unsigned in
}
EXPORT_SYMBOL(__kmalloc);
+void *__kmalloc_gfp_kernel(size_t size)
+{
+ return __kmalloc(size, GFP_KERNEL);
+}
+EXPORT_SYMBOL(__kmalloc_gfp_kernel);
+
#ifdef CONFIG_SMP
/**
* __alloc_percpu - allocate one copy of the object for every present
@@ -2985,14 +2997,20 @@ EXPORT_SYMBOL(kmem_cache_free);
* @size: how many bytes of memory are required.
* @flags: the type of memory to allocate.
*/
-void *kzalloc(size_t size, unsigned int __nocast flags)
+void *__kzalloc(size_t size, unsigned int __nocast flags)
{
void *ret = kmalloc(size, flags);
if (ret)
memset(ret, 0, size);
return ret;
}
-EXPORT_SYMBOL(kzalloc);
+EXPORT_SYMBOL(__kzalloc);
+
+void *__kzalloc_gfp_kernel(size_t size)
+{
+ return __kzalloc(size, GFP_KERNEL);
+}
+EXPORT_SYMBOL(__kzalloc_gfp_kernel);
/**
* kfree - free previously allocated memory
-
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