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Fri, 05 Jun 2026 08:36:11 -0700 (PDT) From: Joshua Hahn To: Johannes Weiner , Michal Hocko Cc: Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: [PATCH 6/6 v3] mm/memcontrol: remove unused memcg_stock code Date: Fri, 5 Jun 2026 08:36:02 -0700 Message-ID: <20260605153603.234296-7-joshua.hahnjy@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260605153603.234296-1-joshua.hahnjy@gmail.com> References: <20260605153603.234296-1-joshua.hahnjy@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Now that all memcg_stock logic has been moved to page_counter_stock, we can remove all code related to handling memcg_stock. Note that obj_stock is untouched and is still needed. FLUSHING_CACHED_CHARGE is preserved so that it can be used by obj_stock as well. Suggested-by: Johannes Weiner Signed-off-by: Joshua Hahn --- mm/memcontrol.c | 186 ------------------------------------------------ 1 file changed, 186 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index d0da2f842e2d4..3e3f8fbd19a48 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1998,25 +1998,7 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg) pr_cont(" are going to be killed due to memory.oom.group set\n"); } -/* - * The value of NR_MEMCG_STOCK is selected to keep the cached memcgs and their - * nr_pages in a single cacheline. This may change in future. - */ -#define NR_MEMCG_STOCK 7 #define FLUSHING_CACHED_CHARGE 0 -struct memcg_stock_pcp { - local_trylock_t lock; - uint8_t nr_pages[NR_MEMCG_STOCK]; - struct mem_cgroup *cached[NR_MEMCG_STOCK]; - - struct work_struct work; - unsigned long flags; - uint8_t drain_idx; -}; - -static DEFINE_PER_CPU_ALIGNED(struct memcg_stock_pcp, memcg_stock) = { - .lock = INIT_LOCAL_TRYLOCK(lock), -}; /* * NR_OBJ_STOCK is sized so the entire hot path of obj_stock_pcp @@ -2065,47 +2047,6 @@ static void drain_obj_stock(struct obj_stock_pcp *stock); static bool obj_stock_flush_required(struct obj_stock_pcp *stock, struct mem_cgroup *root_memcg); -/** - * consume_stock: Try to consume stocked charge on this cpu. - * @memcg: memcg to consume from. - * @nr_pages: how many pages to charge. - * - * Consume the cached charge if enough nr_pages are present otherwise return - * failure. Also return failure for charge request larger than - * MEMCG_CHARGE_BATCH or if the local lock is already taken. - * - * returns true if successful, false otherwise. - */ -static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages) -{ - struct memcg_stock_pcp *stock; - uint8_t stock_pages; - bool ret = false; - int i; - - if (nr_pages > MEMCG_CHARGE_BATCH || - !local_trylock(&memcg_stock.lock)) - return ret; - - stock = this_cpu_ptr(&memcg_stock); - - for (i = 0; i < NR_MEMCG_STOCK; ++i) { - if (memcg != READ_ONCE(stock->cached[i])) - continue; - - stock_pages = READ_ONCE(stock->nr_pages[i]); - if (stock_pages >= nr_pages) { - WRITE_ONCE(stock->nr_pages[i], stock_pages - nr_pages); - ret = true; - } - break; - } - - local_unlock(&memcg_stock.lock); - - return ret; -} - static void memcg_uncharge(struct mem_cgroup *memcg, unsigned int nr_pages) { page_counter_uncharge(&memcg->memory, nr_pages); @@ -2113,51 +2054,6 @@ static void memcg_uncharge(struct mem_cgroup *memcg, unsigned int nr_pages) page_counter_uncharge(&memcg->memsw, nr_pages); } -/* - * Returns stocks cached in percpu and reset cached information. - */ -static void drain_stock(struct memcg_stock_pcp *stock, int i) -{ - struct mem_cgroup *old = READ_ONCE(stock->cached[i]); - uint8_t stock_pages; - - if (!old) - return; - - stock_pages = READ_ONCE(stock->nr_pages[i]); - if (stock_pages) { - memcg_uncharge(old, stock_pages); - WRITE_ONCE(stock->nr_pages[i], 0); - } - - css_put(&old->css); - WRITE_ONCE(stock->cached[i], NULL); -} - -static void drain_stock_fully(struct memcg_stock_pcp *stock) -{ - int i; - - for (i = 0; i < NR_MEMCG_STOCK; ++i) - drain_stock(stock, i); -} - -static void drain_local_memcg_stock(struct work_struct *dummy) -{ - struct memcg_stock_pcp *stock; - - if (WARN_ONCE(!in_task(), "drain in non-task context")) - return; - - local_lock(&memcg_stock.lock); - - stock = this_cpu_ptr(&memcg_stock); - drain_stock_fully(stock); - clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags); - - local_unlock(&memcg_stock.lock); -} - static void drain_local_obj_stock(struct work_struct *dummy) { struct obj_stock_pcp *stock; @@ -2174,88 +2070,6 @@ static void drain_local_obj_stock(struct work_struct *dummy) local_unlock(&obj_stock.lock); } -static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) -{ - struct memcg_stock_pcp *stock; - struct mem_cgroup *cached; - uint8_t stock_pages; - bool success = false; - int empty_slot = -1; - int i; - - /* - * For now limit MEMCG_CHARGE_BATCH to 127 and less. In future if we - * decide to increase it more than 127 then we will need more careful - * handling of nr_pages[] in struct memcg_stock_pcp. - */ - BUILD_BUG_ON(MEMCG_CHARGE_BATCH > S8_MAX); - - VM_WARN_ON_ONCE(mem_cgroup_is_root(memcg)); - - if (nr_pages > MEMCG_CHARGE_BATCH || - !local_trylock(&memcg_stock.lock)) { - /* - * In case of larger than batch refill or unlikely failure to - * lock the percpu memcg_stock.lock, uncharge memcg directly. - */ - memcg_uncharge(memcg, nr_pages); - return; - } - - stock = this_cpu_ptr(&memcg_stock); - for (i = 0; i < NR_MEMCG_STOCK; ++i) { - cached = READ_ONCE(stock->cached[i]); - if (!cached && empty_slot == -1) - empty_slot = i; - if (memcg == READ_ONCE(stock->cached[i])) { - stock_pages = READ_ONCE(stock->nr_pages[i]) + nr_pages; - WRITE_ONCE(stock->nr_pages[i], stock_pages); - if (stock_pages > MEMCG_CHARGE_BATCH) - drain_stock(stock, i); - success = true; - break; - } - } - - if (!success) { - i = empty_slot; - if (i == -1) { - i = stock->drain_idx++; - if (stock->drain_idx == NR_MEMCG_STOCK) - stock->drain_idx = 0; - drain_stock(stock, i); - } - css_get(&memcg->css); - WRITE_ONCE(stock->cached[i], memcg); - WRITE_ONCE(stock->nr_pages[i], nr_pages); - } - - local_unlock(&memcg_stock.lock); -} - -static bool is_memcg_drain_needed(struct memcg_stock_pcp *stock, - struct mem_cgroup *root_memcg) -{ - struct mem_cgroup *memcg; - bool flush = false; - int i; - - rcu_read_lock(); - for (i = 0; i < NR_MEMCG_STOCK; ++i) { - memcg = READ_ONCE(stock->cached[i]); - if (!memcg) - continue; - - if (READ_ONCE(stock->nr_pages[i]) && - mem_cgroup_is_descendant(memcg, root_memcg)) { - flush = true; - break; - } - } - rcu_read_unlock(); - return flush; -} - static void schedule_drain_work(int cpu, struct work_struct *work) { /* -- 2.53.0-Meta