On Fri, 4 Dec 2015 11:17:02 -0600 (CST)
Christoph Lameter <cl@xxxxxxxxx> wrote:
> On Thu, 3 Dec 2015, Jesper Dangaard Brouer wrote:
>
> > +void kmem_cache_free_bulk(struct kmem_cache *orig_s, size_t size, void **p)
>
> orig_s? Thats strange
>
> > +{
> > + struct kmem_cache *s;
>
> s?
The "s" comes from the slub.c code uses "struct kmem_cache *s" everywhere.
> > + size_t i;
> > +
> > + local_irq_disable();
> > + for (i = 0; i < size; i++) {
> > + void *objp = p[i];
> > +
> > + s = cache_from_obj(orig_s, objp);
>
> Does this support freeing objects from a set of different caches?
This is for supporting memcg (CONFIG_MEMCG_KMEM).
Quoting from commit 033745189b1b ("slub: add missing kmem cgroup
support to kmem_cache_free_bulk"):
Incoming bulk free objects can belong to different kmem cgroups, and
object free call can happen at a later point outside memcg context. Thus,
we need to keep the orig kmem_cache, to correctly verify if a memcg object
match against its "root_cache" (s->memcg_params.root_cache).
> > +
> > + debug_check_no_locks_freed(objp, s->object_size);
> > + if (!(s->flags & SLAB_DEBUG_OBJECTS))
> > + debug_check_no_obj_freed(objp, s->object_size);
> > +
> > + __cache_free(s, objp, _RET_IP_);
>
> The function could be further optimized if you take the code from
> __cache_free() and move stuff outside of the loop. The alien cache check
> f.e. and the Pfmemalloc checking may be moved out. The call to
> virt_to_head page may also be avoided if the objects are on the same
> page as the last. So you may be able to function calls for the
> fastpath in the inner loop which may accelerate frees significantly.
Interesting! Maybe we can do a followup patch to pullout last
optimization's. Right now I'm mostly interested in correctness and
clean code. And we are already looking at a 80% speedup with these
patches ;-)
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
Author of http://www.iptv-analyzer.org
LinkedIn: http://www.linkedin.com/in/brouer
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