OpenVZ Forum


Home » Mailing lists » Devel » [PATCH v3 00/16] slab accounting for memcg
Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache [message #48017 is a reply to message #48001] Mon, 24 September 2012 17:58 Go to previous messageGo to previous message
Tejun Heo is currently offline  Tejun Heo
Messages: 184
Registered: November 2006
Senior Member
On Mon, Sep 24, 2012 at 12:17:37PM +0400, Glauber Costa wrote:
> On 09/22/2012 12:52 AM, Tejun Heo wrote:
> > Missed some stuff.
> >
> > On Tue, Sep 18, 2012 at 06:12:00PM +0400, Glauber Costa wrote:
> >> +static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
> >> + struct kmem_cache *cachep)
> >> +{
> > ...
> >> + memcg->slabs[idx] = new_cachep;
> > ...
> >> +struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep,
> >> + gfp_t gfp)
> >> +{
> > ...
> >> + return memcg->slabs[idx];
> >
> > I think you need memory barriers for the above pair.
> >
> > Thanks.
> >
>
> Why is that?
>
> We'll either see a value, or NULL. If we see NULL, we assume the cache
> is not yet created. Not a big deal.

Because when you see !NULL cache pointer you want to be able to see
the cache fully initialized. You need wmb between cache creation and
pointer assignment and at least read_barrier_depends() between
fetching the cache pointer and dereferencing it.

Thanks.

--
tejun
 
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Previous Topic: [PATCH 0/5] nfs: few cleanup patches inspired by sparse
Next Topic: [PATCH v3 04/13] kmem accounting basic infrastructure
Goto Forum:
  


Current Time: Wed Oct 02 16:25:27 GMT 2024

Total time taken to generate the page: 0.05283 seconds