On Sun, Feb 07, 2016 at 08:27:34PM +0300, Vladimir Davydov wrote: > Allocation of radix_tree_node objects can be easily triggered from > userspace, so we should account them to memory cgroup. Besides, we need > them accounted for making shadow node shrinker per memcg (see > mm/workingset.c). > > A tricky thing about accounting radix_tree_node objects is that they are > mostly allocated through radix_tree_preload(), so we can't just set > SLAB_ACCOUNT for radix_tree_node_cachep - that would likely result in a > lot of unrelated cgroups using objects from each other's caches. > > One way to overcome this would be making radix tree preloads per memcg, > but that would probably look cumbersome and overcomplicated. > > Instead, we make radix_tree_node_alloc() first try to allocate from the > cache with __GFP_ACCOUNT, no matter if the caller has preloaded or not, > and only if it fails fall back on using per cpu preloads. This should > make most allocations accounted. > > Signed-off-by: Vladimir Davydov <vdavy...@virtuozzo.com>
Acked-by: Johannes Weiner <han...@cmpxchg.org> I'm not too stoked about the extra slab call. But the preload call allocates nodes for the worst-case insertion, so you are absolutely right that charging there would not make sense for cgroup ownership. And I can't think of anything better to do here.
