On Thu, Mar 18, 2021 at 4:08 AM Muchun Song <songmuchun@xxxxxxxxxxxxx> wrote:
>
[...]
>
> +static inline struct mem_cgroup *get_obj_cgroup_memcg(struct obj_cgroup *objcg)
I would prefer get_mem_cgroup_from_objcg().
> +{
> + struct mem_cgroup *memcg;
> +
> + rcu_read_lock();
> +retry:
> + memcg = obj_cgroup_memcg(objcg);
> + if (unlikely(!css_tryget(&memcg->css)))
> + goto retry;
> + rcu_read_unlock();
> +
> + return memcg;
> +}
> +
> #ifdef CONFIG_MEMCG_KMEM
> int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
> gfp_t gfp, bool new_page)
> @@ -3070,15 +3088,8 @@ static int obj_cgroup_charge_pages(struct obj_cgroup *objcg, gfp_t gfp,
> struct mem_cgroup *memcg;
> int ret;
>
> - rcu_read_lock();
> -retry:
> - memcg = obj_cgroup_memcg(objcg);
> - if (unlikely(!css_tryget(&memcg->css)))
> - goto retry;
> - rcu_read_unlock();
> -
> + memcg = get_obj_cgroup_memcg(objcg);
> ret = __memcg_kmem_charge(memcg, gfp, nr_pages);
Why not manually inline __memcg_kmem_charge() here? This is the only user.
Similarly manually inline __memcg_kmem_uncharge() into
obj_cgroup_uncharge_pages() and call obj_cgroup_uncharge_pages() in
obj_cgroup_release().
> -
> css_put(&memcg->css);
>
> return ret;
> @@ -3143,18 +3154,18 @@ static void __memcg_kmem_uncharge(struct mem_cgroup *memcg, unsigned int nr_page
> */
> int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order)
> {
> - struct mem_cgroup *memcg;
> + struct obj_cgroup *objcg;
> int ret = 0;
>
> - memcg = get_mem_cgroup_from_current();
This was the only use of get_mem_cgroup_from_current(). Why not remove it?
> - if (memcg && !mem_cgroup_is_root(memcg)) {
> - ret = __memcg_kmem_charge(memcg, gfp, 1 << order);
> + objcg = get_obj_cgroup_from_current();
> + if (objcg) {
> + ret = obj_cgroup_charge_pages(objcg, gfp, 1 << order);
> if (!ret) {
> - page->memcg_data = (unsigned long)memcg |
> + page->memcg_data = (unsigned long)objcg |
> MEMCG_DATA_KMEM;
> return 0;
> }
> - css_put(&memcg->css);
> + obj_cgroup_put(objcg);
> }
> return ret;
> }
[...]
> static void uncharge_page(struct page *page, struct uncharge_gather *ug)
> {
> unsigned long nr_pages;
> + struct mem_cgroup *memcg;
> + struct obj_cgroup *objcg;
>
> VM_BUG_ON_PAGE(PageLRU(page), page);
>
> - if (!page_memcg(page))
> - return;
> -
> /*
> * Nobody should be changing or seriously looking at
> - * page_memcg(page) at this point, we have fully
> + * page memcg or objcg at this point, we have fully
> * exclusive access to the page.
> */
> + if (PageMemcgKmem(page)) {
> + objcg = __page_objcg(page);
> + memcg = get_obj_cgroup_memcg(objcg);
Can you add a comment that this get matches the put at the end of the
function and kmem pages do not hold memcg references anymore.
> + } else {
> + memcg = __page_memcg(page);
> + }
> +
> + if (!memcg)
> + return;
>
> - if (ug->memcg != page_memcg(page)) {
> + if (ug->memcg != memcg) {
> if (ug->memcg) {
> uncharge_batch(ug);
> uncharge_gather_clear(ug);
> }
> - ug->memcg = page_memcg(page);
> + ug->memcg = memcg;
> ug->dummy_page = page;
>
> /* pairs with css_put in uncharge_batch */
> - css_get(&ug->memcg->css);
> + css_get(&memcg->css);
> }
>
> nr_pages = compound_nr(page);
> - ug->nr_pages += nr_pages;
>
> - if (PageMemcgKmem(page))
> + if (PageMemcgKmem(page)) {
> + ug->nr_memory += nr_pages;
> ug->nr_kmem += nr_pages;
> - else
> +
> + page->memcg_data = 0;
> + obj_cgroup_put(objcg);
> + } else {
> + /* LRU pages aren't accounted at the root level */
> + if (!mem_cgroup_is_root(memcg))
> + ug->nr_memory += nr_pages;
> ug->pgpgout++;
>
> - page->memcg_data = 0;
> - css_put(&ug->memcg->css);
> + page->memcg_data = 0;
> + }
> +
> + css_put(&memcg->css);
> }
>
> /**
> --
> 2.11.0
>
