Re: [PATCH v3 19/28] slab: per-memcg accounting of slab caches

[Glauber Costa]

On 05/29/2012 08:07 PM, Glauber Costa wrote:
> On 05/29/2012 06:52 PM, Christoph Lameter wrote:
> > On Fri, 25 May 2012, Glauber Costa wrote:
> >
> > > > This patch charges allocation of a slab object to a particular
> > > > memcg.
> > Ok so a requirement is to support tracking of individual slab
> > objects to cgroups? That is going to be quite expensive since it will
> > touch the hotpaths.
>
> No, we track pages. But all the objects in the page belong to the same
> cgroup.

Also, please note the following:

The code that relays us to the right cache, is wrapped inside a static 
branch. Whoever is not using more than the root cgroup, will not suffer 
a single bit.

If you are, but your process is in the right cgroup, you will 
unfortunately pay function call penalty(*), but the code will make and 
effort to detect that as early as possible and resume.


(*) Not even then if you fall in the following categories, that are 
resolved inline:

+       if (!current->mm)
+               return cachep;
+       if (in_interrupt())
+               return cachep;
+       if (gfp & __GFP_NOFAIL)
+               return cachep;

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