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charset="UTF-8" X-Rspamd-Queue-Id: 317FE180AD801 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jun 8, 2020 at 4:07 PM Roman Gushchin wrote: > > Instead of having two sets of kmem_caches: one for system-wide and > non-accounted allocations and the second one shared by all accounted > allocations, we can use just one. > > The idea is simple: space for obj_cgroup metadata can be allocated > on demand and filled only for accounted allocations. > > It allows to remove a bunch of code which is required to handle > kmem_cache clones for accounted allocations. There is no more need > to create them, accumulate statistics, propagate attributes, etc. > It's a quite significant simplification. > > Also, because the total number of slab_caches is reduced almost twice > (not all kmem_caches have a memcg clone), some additional memory > savings are expected. On my devvm it additionally saves about 3.5% > of slab memory. > > Suggested-by: Johannes Weiner > Signed-off-by: Roman Gushchin > Reviewed-by: Vlastimil Babka > --- [snip] > static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s, > struct obj_cgroup *objcg, > - size_t size, void **p) > + gfp_t flags, size_t size, > + void **p) > { > struct page *page; > unsigned long off; > size_t i; > > + if (!objcg) > + return; > + > + flags &= ~__GFP_ACCOUNT; > for (i = 0; i < size; i++) { > if (likely(p[i])) { > page = virt_to_head_page(p[i]); > + > + if (!page_has_obj_cgroups(page) && The page is already linked into the kmem_cache, don't you need synchronization for memcg_alloc_page_obj_cgroups(). What's the reason to remove this from charge_slab_page()? > + memcg_alloc_page_obj_cgroups(page, s, flags)) { > + obj_cgroup_uncharge(objcg, obj_full_size(s)); > + continue; > + } > + > off = obj_to_index(s, page, p[i]); > obj_cgroup_get(objcg); > page_obj_cgroups(page)[off] = objcg;