On Fri, Sep 06, 2024 at 10:52:04AM GMT, Vlastimil Babka wrote: > On 9/5/24 20:48, Shakeel Butt wrote: > >> > --- > >> > v3: https://lore.kernel.org/all/20240829175339.2424521-1-shakeel.butt@xxxxxxxxx/ > >> > Changes since v3: > >> > - Add kernel doc for kmem_cache_charge. > >> > > >> > v2: https://lore.kernel.org/all/20240827235228.1591842-1-shakeel.butt@xxxxxxxxx/ > >> > Change since v2: > >> > - Add handling of already charged large kmalloc objects. > >> > - Move the normal kmalloc cache check into a function. > >> > > >> > v1: https://lore.kernel.org/all/20240826232908.4076417-1-shakeel.butt@xxxxxxxxx/ > >> > Changes since v1: > >> > - Correctly handle large allocations which bypass slab > >> > - Rearrange code to avoid compilation errors for !CONFIG_MEMCG builds > >> > > >> > RFC: https://lore.kernel.org/all/20240824010139.1293051-1-shakeel.butt@xxxxxxxxx/ > >> > Changes since the RFC: > >> > - Added check for already charged slab objects. > >> > - Added performance results from neper's tcp_crr > >> > > >> > > >> > include/linux/slab.h | 20 ++++++++++++++ > >> > mm/slab.h | 7 +++++ > >> > mm/slub.c | 49 +++++++++++++++++++++++++++++++++ > >> > net/ipv4/inet_connection_sock.c | 5 ++-- > >> > 4 files changed, 79 insertions(+), 2 deletions(-) > >> > > >> > diff --git a/include/linux/slab.h b/include/linux/slab.h > >> > index eb2bf4629157..68789c79a530 100644 > >> > --- a/include/linux/slab.h > >> > +++ b/include/linux/slab.h > >> > @@ -547,6 +547,26 @@ void *kmem_cache_alloc_lru_noprof(struct kmem_cache *s, struct list_lru *lru, > >> > gfp_t gfpflags) __assume_slab_alignment __malloc; > >> > #define kmem_cache_alloc_lru(...) alloc_hooks(kmem_cache_alloc_lru_noprof(__VA_ARGS__)) > >> > > >> > +/** > >> > + * 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 is the normal method to charge a slab object to the current > > what is "normal method"? This is just a copy-paste from kmalloc() documentation. > > >> > + * memcg. The objp should be pointer returned by the slab allocator functions > >> > + * like kmalloc or kmem_cache_alloc. The memcg charge behavior can be controller > >> > >> s/controller/controlled > > > > Thanks. Vlastimil please fix this when you pick this up. > > 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 > * 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. > */ > Yes, this is much better. > >> > + > >> > + /* 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. > */ > Looks great to me. thanks, Shakeel
