[Devel] [PATCH -mm 1/4] sl[au]b: do not charge large allocations to memcg

[Vladimir Davydov]

Hi Michal,

On 03/27/2014 01:53 AM, Michal Hocko wrote:
> On Wed 26-03-14 19:28:04, Vladimir Davydov wrote:
>> We don't track any random page allocation, so we shouldn't track kmalloc
>> that falls back to the page allocator.
> Why did we do that in the first place? d79923fad95b (sl[au]b: allocate
> objects from memcg cache) didn't tell me much.

I don't know, we'd better ask Glauber about that.

> How is memcg_kmem_skip_account removal related?

The comment this patch removes along with the memcg_kmem_skip_account
check explains that pretty well IMO. In short, we only use
memcg_kmem_skip_account to prevent kmalloc's from charging, which is
crucial for recursion-avoidance in memcg_kmem_get_cache. Since we don't
charge pages allocated from a root (not per-memcg) cache, from the first
glance it would be enough to check for memcg_kmem_skip_account only in
memcg_kmem_get_cache and return the root cache if it's set. However, for
we can also kmalloc w/o issuing memcg_kmem_get_cache (kmalloc_large), we
also need this check in memcg_kmem_newpage_charge. This patch removes
kmalloc_large accounting, so we don't need this check anymore.

Thanks.