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Date: Wed, 12 Feb 2025 09:47:03 -0800 Message-Id: <20250212174705.44492-5-alexei.starovoitov@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20250212174705.44492-1-alexei.starovoitov@gmail.com> References: <20250212174705.44492-1-alexei.starovoitov@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net From: Alexei Starovoitov Teach memcg to operate under trylock conditions when spinning locks cannot be used. localtry_trylock might fail and this would lead to charge cache bypass if the calling context doesn't allow spinning (gfpflags_allow_spinning). In those cases charge the memcg counter directly and fail early if that is not possible. This might cause a pre-mature charge failing but it will allow an opportunistic charging that is safe from try_alloc_pages path. Acked-by: Michal Hocko Acked-by: Vlastimil Babka Acked-by: Shakeel Butt Signed-off-by: Alexei Starovoitov --- mm/memcontrol.c | 52 ++++++++++++++++++++++++++++++++++--------------- 1 file changed, 36 insertions(+), 16 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 7b3503d12aaf..f3af615f727c 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1722,7 +1722,7 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg) } struct memcg_stock_pcp { - local_lock_t stock_lock; + localtry_lock_t stock_lock; struct mem_cgroup *cached; /* this never be root cgroup */ unsigned int nr_pages; @@ -1737,7 +1737,7 @@ struct memcg_stock_pcp { #define FLUSHING_CACHED_CHARGE 0 }; static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock) = { - .stock_lock = INIT_LOCAL_LOCK(stock_lock), + .stock_lock = INIT_LOCALTRY_LOCK(stock_lock), }; static DEFINE_MUTEX(percpu_charge_mutex); @@ -1756,7 +1756,8 @@ static bool obj_stock_flush_required(struct memcg_stock_pcp *stock, * * returns true if successful, false otherwise. */ -static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages) +static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages, + gfp_t gfp_mask) { struct memcg_stock_pcp *stock; unsigned int stock_pages; @@ -1766,7 +1767,11 @@ static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages) if (nr_pages > MEMCG_CHARGE_BATCH) return ret; - local_lock_irqsave(&memcg_stock.stock_lock, flags); + if (!localtry_trylock_irqsave(&memcg_stock.stock_lock, flags)) { + if (!gfpflags_allow_spinning(gfp_mask)) + return ret; + localtry_lock_irqsave(&memcg_stock.stock_lock, flags); + } stock = this_cpu_ptr(&memcg_stock); stock_pages = READ_ONCE(stock->nr_pages); @@ -1775,7 +1780,7 @@ static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages) ret = true; } - local_unlock_irqrestore(&memcg_stock.stock_lock, flags); + localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags); return ret; } @@ -1814,14 +1819,14 @@ static void drain_local_stock(struct work_struct *dummy) * drain_stock races is that we always operate on local CPU stock * here with IRQ disabled */ - local_lock_irqsave(&memcg_stock.stock_lock, flags); + localtry_lock_irqsave(&memcg_stock.stock_lock, flags); stock = this_cpu_ptr(&memcg_stock); old = drain_obj_stock(stock); drain_stock(stock); clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags); - local_unlock_irqrestore(&memcg_stock.stock_lock, flags); + localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags); obj_cgroup_put(old); } @@ -1851,9 +1856,20 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) { unsigned long flags; - local_lock_irqsave(&memcg_stock.stock_lock, flags); + if (!localtry_trylock_irqsave(&memcg_stock.stock_lock, flags)) { + /* + * In case of unlikely failure to lock percpu stock_lock + * uncharge memcg directly. + */ + if (mem_cgroup_is_root(memcg)) + return; + page_counter_uncharge(&memcg->memory, nr_pages); + if (do_memsw_account()) + page_counter_uncharge(&memcg->memsw, nr_pages); + return; + } __refill_stock(memcg, nr_pages); - local_unlock_irqrestore(&memcg_stock.stock_lock, flags); + localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags); } /* @@ -2196,9 +2212,13 @@ int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, unsigned long pflags; retry: - if (consume_stock(memcg, nr_pages)) + if (consume_stock(memcg, nr_pages, gfp_mask)) return 0; + if (!gfpflags_allow_spinning(gfp_mask)) + /* Avoid the refill and flush of the older stock */ + batch = nr_pages; + if (!do_memsw_account() || page_counter_try_charge(&memcg->memsw, batch, &counter)) { if (page_counter_try_charge(&memcg->memory, batch, &counter)) @@ -2709,7 +2729,7 @@ static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat, unsigned long flags; int *bytes; - local_lock_irqsave(&memcg_stock.stock_lock, flags); + localtry_lock_irqsave(&memcg_stock.stock_lock, flags); stock = this_cpu_ptr(&memcg_stock); /* @@ -2762,7 +2782,7 @@ static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat, if (nr) __mod_objcg_mlstate(objcg, pgdat, idx, nr); - local_unlock_irqrestore(&memcg_stock.stock_lock, flags); + localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags); obj_cgroup_put(old); } @@ -2772,7 +2792,7 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes) unsigned long flags; bool ret = false; - local_lock_irqsave(&memcg_stock.stock_lock, flags); + localtry_lock_irqsave(&memcg_stock.stock_lock, flags); stock = this_cpu_ptr(&memcg_stock); if (objcg == READ_ONCE(stock->cached_objcg) && stock->nr_bytes >= nr_bytes) { @@ -2780,7 +2800,7 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes) ret = true; } - local_unlock_irqrestore(&memcg_stock.stock_lock, flags); + localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags); return ret; } @@ -2872,7 +2892,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes, unsigned long flags; unsigned int nr_pages = 0; - local_lock_irqsave(&memcg_stock.stock_lock, flags); + localtry_lock_irqsave(&memcg_stock.stock_lock, flags); stock = this_cpu_ptr(&memcg_stock); if (READ_ONCE(stock->cached_objcg) != objcg) { /* reset if necessary */ @@ -2890,7 +2910,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes, stock->nr_bytes &= (PAGE_SIZE - 1); } - local_unlock_irqrestore(&memcg_stock.stock_lock, flags); + localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags); obj_cgroup_put(old); if (nr_pages)