[..] > I felt it could be improved more, so ended up with this. Thoughts? > > /** > * kmem_cache_charge - memcg charge an already allocated slab memory > * @objp: address of the slab object to memcg charge > * @gfpflags: describe the allocation context > * > * kmem_cache_charge allows charging a slab object to the current memcg, > * primarily in cases where charging at allocation time might not be possible > * because the target memcg is not known (i.e. softirq context) > * > * The objp should be pointer returned by the slab allocator functions like > * kmalloc (with __GFP_ACCOUNT in flags) or kmem_cache_alloc. The memcg charge Aren't allocations done with kmalloc(__GFP_ACCOUNT) already accounted? Why would we need to call kmem_cache_charge() for those? I am assuming what you are referring to is kmalloc() allocations that are not fulfilled from KMALLOC_NORMAL caches, but I am not sure how to capture this here. > * behavior can be controlled through gfpflags parameter, which affects how the > * necessary internal metadata can be allocated. Including __GFP_NOFAIL denotes > * that overcharging is requested instead of failure, but is not applied for the > * internal metadata allocation. > * > * There are several cases where it will return true even if the charging was > * not done: > * More specifically: > * > * 1. For !CONFIG_MEMCG or cgroup_disable=memory systems. > * 2. Already charged slab objects. > * 3. For slab objects from KMALLOC_NORMAL caches - allocated by kmalloc() > * without __GFP_ACCOUNT > * 4. Allocating internal metadata has failed > * > * Return: true if charge was successful otherwise false. > */ > > >> > + > >> > + /* Ignore KMALLOC_NORMAL cache to avoid circular dependency. */ > >> > >> Is it possible to point to the commit that has the explanation here? > >> The one you pointed me to before? Otherwise it's not really obvious > >> where the circular dependency comes from (at least to me). > >> > > > > Not sure about the commit reference. We can add more text here. > > Vlastimil, how much detail do you prefer? > > What about: > > /* > * Ignore KMALLOC_NORMAL cache to avoid possible circular dependency > * of slab_obj_exts being allocated from the same slab and thus the slab > * becoming effectively unfreeable. > */ > > > > thanks, > > Shakeel >
