On Wed, Jan 16, 2013 at 03:20:57PM +0000, Christoph Lameter wrote:
> On Wed, 16 Jan 2013, Liu Bo wrote:
>
> > --- a/include/linux/slub_def.h
> > +++ b/include/linux/slub_def.h
> > @@ -93,6 +93,7 @@ struct kmem_cache {
> > gfp_t allocflags; /* gfp flags to use on each alloc */
> > int refcount; /* Refcount for slab cache destroy */
> > void (*ctor)(void *);
> > + void (*decoder)(void *);
>
> The field needs to be moved away from the first hot cachelines in
> kmem_cache.
>
>
> > index 3f3cd97..8c19bfd 100644
> > --- a/mm/slab_common.c
> > +++ b/mm/slab_common.c
> > @@ -193,6 +193,7 @@ kmem_cache_create_memcg(struct mem_cgroup *memcg, const char *name, size_t size,
> > s->object_size = s->size = size;
> > s->align = calculate_alignment(flags, align, size);
> > s->ctor = ctor;
> > + s->decoder = NULL;
> >
> > if (memcg_register_cache(memcg, s, parent_cache)) {
> > kmem_cache_free(kmem_cache, s);
>
> Not necessary since s is filled with zeros on allocation.
>
> > @@ -248,7 +249,7 @@ kmem_cache_create(const char *name, size_t size, size_t align,
> > }
> > EXPORT_SYMBOL(kmem_cache_create);
> >
> > -void kmem_cache_destroy(struct kmem_cache *s)
> > +static void __kmem_cache_destroy(struct kmem_cache *s, void (*decoder)(void *))
> > {
> > /* Destroy all the children caches if we aren't a memcg cache */
> > kmem_cache_destroy_memcg_children(s);
> > @@ -259,6 +260,9 @@ void kmem_cache_destroy(struct kmem_cache *s)
> > if (!s->refcount) {
> > list_del(&s->list);
> >
> > + if (unlikely(decoder))
> > + s->decoder = decoder;
> > +
> > if (!__kmem_cache_shutdown(s)) {
> > mutex_unlock(&slab_mutex);
> > if (s->flags & SLAB_DESTROY_BY_RCU)
>
> Now that is a bit weird since __kmem_cache_destroy now sets a field in
> kmem_cache?
>
> If a kmem_cache has a decoder field set then it is no longer mergeable.
>
> It looks like the decoder field would have to be set on cache creation.
>
> If we do that then the functionality could be more generic. I always
> wanted to have a function that checks the object integrity as well.
>
> The cache validation could then go through all objects and in addition to
> checking the slab meta data integrity could also have the subsystem
> confirm the integrity of the object.
Hmm...right, seems that we have to set the decoder field on creation
part, it brings us lots of API update though.
>
> > index ba2ca53..34b3b75 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -3098,6 +3098,8 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page,
> > for_each_object(p, s, addr, page->objects) {
> >
> > if (!test_bit(slab_index(p, s, addr), map)) {
> > + if (unlikely(s->decoder))
> > + s->decoder(p);
> > printk(KERN_ERR "INFO: Object 0x%p @offset=%tu\n",
> > p, p - addr);
> > print_tracking(s, p);
> >
>
> Hmmm... The function is currently only used on kmem_cache_destroy but that
> may change.
Good point.
list_slab_objects(struct kmem_cache *, struct page *, const char *,
void (*)(void *))
what about this? At least we can interpret the objects as we want.
thanks,
liubo
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