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SubjectRe: [PATCH] vmalloc : optimization, cleanup, bugfixes
Date
On Monday 23 October 2006 11:13, Nick Piggin wrote:
> Eric Dumazet wrote:
> > 3) Bugfixes in vmalloc_user() and vmalloc_32_user()
> > NULL returns from __vmalloc() and __find_vm_area() were not tested.
>
> Hmm, so they weren't. As far as testing the return of __find_vm_area,
> you can just turn that into a BUG_ON(!area), because at that point,
> we've established that the vmalloc succeeded.

OK :)

[PATCH] vmalloc : optimization, cleanup, bugfixes

This patch does three things

1) reorder 'struct vm_struct' to speedup lookups on CPUS with small cache
lines. The fields 'next,addr,size' should be now in the same cache line, to
speedup lookups.

2) One minor cleanup in __get_vm_area_node()

3) Bugfixes in vmalloc_user() and vmalloc_32_user()
NULL returns from __vmalloc() and __find_vm_area() were not tested.


Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
--- linux-2.6/include/linux/vmalloc.h 2006-10-23 10:09:48.000000000 +0200
+++ linux-2.6-ed/include/linux/vmalloc.h 2006-10-23 10:26:37.000000000 +0200
@@ -23,13 +23,14 @@
#endif

struct vm_struct {
+ /* keep next,addr,size together to speedup lookups */
+ struct vm_struct *next;
void *addr;
unsigned long size;
unsigned long flags;
struct page **pages;
unsigned int nr_pages;
unsigned long phys_addr;
- struct vm_struct *next;
};

/*
--- linux-2.6/mm/vmalloc.c 2006-10-23 10:11:43.000000000 +0200
+++ linux-2.6-ed/mm/vmalloc.c 2006-10-23 11:26:47.000000000 +0200
@@ -180,15 +180,13 @@
addr = ALIGN(start, align);
size = PAGE_ALIGN(size);

+ if (unlikely(!size))
+ return NULL;
+
area = kmalloc_node(sizeof(*area), GFP_KERNEL, node);
if (unlikely(!area))
return NULL;

- if (unlikely(!size)) {
- kfree (area);
- return NULL;
- }
-
/*
* We always allocate a guard page.
*/
@@ -528,11 +526,13 @@
void *ret;

ret = __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO, PAGE_KERNEL);
- write_lock(&vmlist_lock);
- area = __find_vm_area(ret);
- area->flags |= VM_USERMAP;
- write_unlock(&vmlist_lock);
-
+ if (ret) {
+ write_lock(&vmlist_lock);
+ area = __find_vm_area(ret);
+ BUG_ON(!area);
+ area->flags |= VM_USERMAP;
+ write_unlock(&vmlist_lock);
+ }
return ret;
}
EXPORT_SYMBOL(vmalloc_user);
@@ -601,11 +601,13 @@
void *ret;

ret = __vmalloc(size, GFP_KERNEL | __GFP_ZERO, PAGE_KERNEL);
- write_lock(&vmlist_lock);
- area = __find_vm_area(ret);
- area->flags |= VM_USERMAP;
- write_unlock(&vmlist_lock);
-
+ if (ret) {
+ write_lock(&vmlist_lock);
+ area = __find_vm_area(ret);
+ BUG_ON(!area);
+ area->flags |= VM_USERMAP;
+ write_unlock(&vmlist_lock);
+ }
return ret;
}
EXPORT_SYMBOL(vmalloc_32_user);
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