Messages in this thread | | | Date | Wed, 6 May 2015 15:24:31 +0300 | From | Vladimir Davydov <> | Subject | Re: [PATCH 1/2] gfp: add __GFP_NOACCOUNT |
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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
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