On 2/12/24 22:38, Suren Baghdasaryan wrote: > Currently slab pages can store only vectors of obj_cgroup pointers in > page->memcg_data. Introduce slabobj_ext structure to allow more data > to be stored for each slab object. Wrap obj_cgroup into slabobj_ext > to support current functionality while allowing to extend slabobj_ext > in the future. > > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx> ... > +static inline bool need_slab_obj_ext(void) > +{ > + /* > + * CONFIG_MEMCG_KMEM creates vector of obj_cgroup objects conditionally > + * inside memcg_slab_post_alloc_hook. No other users for now. > + */ > + return false; > +} > + > +static inline struct slabobj_ext * > +prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p) > +{ > + struct slab *slab; > + > + if (!p) > + return NULL; > + > + if (!need_slab_obj_ext()) > + return NULL; > + > + slab = virt_to_slab(p); > + if (!slab_obj_exts(slab) && > + WARN(alloc_slab_obj_exts(slab, s, flags, false), > + "%s, %s: Failed to create slab extension vector!\n", > + __func__, s->name)) > + return NULL; > + > + return slab_obj_exts(slab) + obj_to_index(s, slab, p); This is called in slab_post_alloc_hook() and the result stored to obj_exts but unused. Maybe introduce this only in a later patch where it becomes relevant? > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -201,6 +201,54 @@ struct kmem_cache *find_mergeable(unsigned int size, unsigned int align, > return NULL; > } > > +#ifdef CONFIG_SLAB_OBJ_EXT > +/* > + * The allocated objcg pointers array is not accounted directly. > + * Moreover, it should not come from DMA buffer and is not readily > + * reclaimable. So those GFP bits should be masked off. > + */ > +#define OBJCGS_CLEAR_MASK (__GFP_DMA | __GFP_RECLAIMABLE | \ > + __GFP_ACCOUNT | __GFP_NOFAIL) > + > +int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s, > + gfp_t gfp, bool new_slab) Since you're moving this function between files anyway, could you please instead move it to mm/slub.c. I expect we'll eventually (maybe even soon) move the rest of performance sensitive kmemcg hooks there as well to make inlining possible. > +{ > + unsigned int objects = objs_per_slab(s, slab); > + unsigned long obj_exts; > + void *vec; > + > + gfp &= ~OBJCGS_CLEAR_MASK; > + vec = kcalloc_node(objects, sizeof(struct slabobj_ext), gfp, > + slab_nid(slab)); > + if (!vec) > + return -ENOMEM; > + > + obj_exts = (unsigned long)vec; > +#ifdef CONFIG_MEMCG > + obj_exts |= MEMCG_DATA_OBJEXTS; > +#endif > + if (new_slab) { > + /* > + * If the slab is brand new and nobody can yet access its > + * obj_exts, no synchronization is required and obj_exts can > + * be simply assigned. > + */ > + slab->obj_exts = obj_exts; > + } else if (cmpxchg(&slab->obj_exts, 0, obj_exts)) { > + /* > + * If the slab is already in use, somebody can allocate and > + * assign slabobj_exts in parallel. In this case the existing > + * objcg vector should be reused. > + */ > + kfree(vec); > + return 0; > + } > + > + kmemleak_not_leak(vec); > + return 0; > +} > +#endif /* CONFIG_SLAB_OBJ_EXT */ > + > static struct kmem_cache *create_cache(const char *name, > unsigned int object_size, unsigned int align, > slab_flags_t flags, unsigned int useroffset, > diff --git a/mm/slub.c b/mm/slub.c > index 2ef88bbf56a3..1eb1050814aa 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -683,10 +683,10 @@ static inline bool __slab_update_freelist(struct kmem_cache *s, struct slab *sla > > if (s->flags & __CMPXCHG_DOUBLE) { > ret = __update_freelist_fast(slab, freelist_old, counters_old, > - freelist_new, counters_new); > + freelist_new, counters_new); > } else { > ret = __update_freelist_slow(slab, freelist_old, counters_old, > - freelist_new, counters_new); > + freelist_new, counters_new); > } > if (likely(ret)) > return true; > @@ -710,13 +710,13 @@ static inline bool slab_update_freelist(struct kmem_cache *s, struct slab *slab, > > if (s->flags & __CMPXCHG_DOUBLE) { > ret = __update_freelist_fast(slab, freelist_old, counters_old, > - freelist_new, counters_new); > + freelist_new, counters_new); > } else { > unsigned long flags; > > local_irq_save(flags); > ret = __update_freelist_slow(slab, freelist_old, counters_old, > - freelist_new, counters_new); > + freelist_new, counters_new); I can see the mixing of tabs and spaces is wrong but perhaps not fix it as part of the series? > local_irq_restore(flags); > } > if (likely(ret)) > @@ -1881,13 +1881,25 @@ static inline enum node_stat_item cache_vmstat_idx(struct kmem_cache *s) > NR_SLAB_RECLAIMABLE_B : NR_SLAB_UNRECLAIMABLE_B; > } > > -#ifdef CONFIG_MEMCG_KMEM > -static inline void memcg_free_slab_cgroups(struct slab *slab) > +#ifdef CONFIG_SLAB_OBJ_EXT > +static inline void free_slab_obj_exts(struct slab *slab) Right, freeing is already here, so makes sense put the allocation here as well. > @@ -3817,6 +3820,7 @@ void slab_post_alloc_hook(struct kmem_cache *s, struct obj_cgroup *objcg, > kmemleak_alloc_recursive(p[i], s->object_size, 1, > s->flags, init_flags); > kmsan_slab_alloc(s, p[i], init_flags); > + obj_exts = prepare_slab_obj_exts_hook(s, flags, p[i]); Yeah here's the hook used. Doesn't it generate a compiler warning? Maybe at least postpone the call until the result is further used. > } > > memcg_slab_post_alloc_hook(s, objcg, flags, size, p);