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From: Shakeel Butt To: Alexei Starovoitov Cc: bpf@vger.kernel.org, andrii@kernel.org, memxor@gmail.com, akpm@linux-foundation.org, peterz@infradead.org, vbabka@suse.cz, bigeasy@linutronix.de, rostedt@goodmis.org, houtao1@huawei.com, hannes@cmpxchg.org, mhocko@suse.com, willy@infradead.org, tglx@linutronix.de, jannh@google.com, tj@kernel.org, linux-mm@kvack.org, kernel-team@fb.com Subject: Re: [PATCH bpf-next v5 4/7] memcg: Use trylock to access memcg stock_lock. Message-ID: References: <20250115021746.34691-1-alexei.starovoitov@gmail.com> <20250115021746.34691-5-alexei.starovoitov@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250115021746.34691-5-alexei.starovoitov@gmail.com> X-Migadu-Flow: FLOW_OUT X-Stat-Signature: ricsh9bocz6ye6ozzikyb5ske4cgxm8b X-Rspam-User: X-Rspamd-Queue-Id: B0572140012 X-Rspamd-Server: rspam03 X-HE-Tag: 1736986350-10478 X-HE-Meta: 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 owjIEpuV 7267r6+WJ+a0qgKILXN2h0kcAd3JkDrunrfg9Us52slLQlxDVCEAwMvrDwyYgG26rb3NVMOQSnbAegfCs/pWWXaqab5e8t3wN6ePHB860gr0bAcLi9Uceo4Q9xOPHPtCCWw4j9IT9spCOCTY85glu3jdohV8mc7gwUR8wBFWILnRF1XJU+7bGfrvMc+aND/uW5Q31sPnTeDxdq5HEOf0U+RhkiCxO0JfjWxaUtzXiCWHAYCvSrA0L4zpY9KIK6X/8RFftrGLyFkRQ62hKnvsTp0T2I3OJGJTOHa2PaqzLlv7PY3giw4SN9SusvjCAFA8JJVwEs+YEZL6+9Fds/dQ/nD/FwFokbZSm7rySX7rPfjHiiPApMdG/P5DurtAvuGucyvZA 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: List-Subscribe: List-Unsubscribe: On Tue, Jan 14, 2025 at 06:17:43PM -0800, Alexei Starovoitov wrote: > From: Alexei Starovoitov > > Teach memcg to operate under trylock conditions when spinning locks > cannot be used. > > local_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 > Signed-off-by: Alexei Starovoitov Acked-by: Shakeel Butt > @@ -1851,7 +1856,14 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) > { > unsigned long flags; > > - local_lock_irqsave(&memcg_stock.stock_lock, flags); > + if (!local_trylock_irqsave(&memcg_stock.stock_lock, flags)) { > + /* > + * In case of unlikely failure to lock percpu stock_lock > + * uncharge memcg directly. > + */ > + mem_cgroup_cancel_charge(memcg, nr_pages); mem_cgroup_cancel_charge() has been removed by a patch in mm-tree. Maybe we can either revive mem_cgroup_cancel_charge() or simply inline it here. > + return; > + } > __refill_stock(memcg, nr_pages); > local_unlock_irqrestore(&memcg_stock.stock_lock, flags); > }