lkml.org 
[lkml]   [2015]   [May]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/2] gfp: add __GFP_NOACCOUNT
On Wed, May 06, 2015 at 01:59:41PM +0200, Michal Hocko wrote:
> On Tue 05-05-15 12:45:42, Vladimir Davydov wrote:
> > Not all kmem allocations should be accounted to memcg. The following
> > patch gives an example when accounting of a certain type of allocations
> > to memcg can effectively result in a memory leak.
>
> > This patch adds the __GFP_NOACCOUNT flag which if passed to kmalloc
> > and friends will force the allocation to go through the root
> > cgroup. It will be used by the next patch.
>
> The name of the flag is way too generic. It is not clear that the
> accounting is KMEMCG related. __GFP_NO_KMEMCG sounds better?
>
> I was going to suggest doing per-cache rather than gfp flag and that
> would actually work just fine for the kmemleak as it uses its own cache
> already. But the ida_simple_get would be trickier because it doesn't use
> any special cache and more over only one user seem to have a problem so
> this doesn't sound like a good fit.

I don't think making this flag per-cache is an option either, but for
another reason - it would not be possible to merge such a kmem cache
with caches without this flag set. As a result, total memory pressure
would increase, even for setups without kmem-active memory cgroups,
which does not sound acceptable to me.

>
> So I do not object to opt-out for kmemcg accounting but I really think
> the name should be changed.

I named it __GFP_NOACCOUNT to match with __GFP_NOTRACK, which is a very
specific flag too (kmemcheck), nevertheless it has a rather generic
name.

Anyways, what else apart from memcg can account kmem so that we have to
mention KMEMCG in the flag name explicitly?

Thanks,
Vladimir


\
 
 \ /
  Last update: 2015-05-06 14:41    [W:0.183 / U:0.352 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site