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[109.81.89.64]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-aab9606893esm547480166b.71.2024.12.18.03.32.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Dec 2024 03:32:36 -0800 (PST) Date: Wed, 18 Dec 2024 12:32:35 +0100 From: Michal Hocko To: alexei.starovoitov@gmail.com 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, shakeel.butt@linux.dev, 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 v3 2/6] mm, bpf: Introduce free_pages_nolock() Message-ID: References: <20241218030720.1602449-1-alexei.starovoitov@gmail.com> <20241218030720.1602449-3-alexei.starovoitov@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241218030720.1602449-3-alexei.starovoitov@gmail.com> On Tue 17-12-24 19:07:15, alexei.starovoitov@gmail.com wrote: > From: Alexei Starovoitov > > Introduce free_pages_nolock() that can free pages without taking locks. > It relies on trylock and can be called from any context. > Since spin_trylock() cannot be used in RT from hard IRQ or NMI > it uses lockless link list to stash the pages which will be freed > by subsequent free_pages() from good context. Yes, this makes sense. Have you tried a simpler implementation that would just queue on the lockless link list unconditionally? That would certainly reduce the complexity. Essentially something similar that we do in vfree_atomic (well, except the queue_work which is likely too heavy for the usecase and potentialy not reentrant). -- Michal Hocko SUSE Labs