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b=GaITvt0Rown3AjtLBBDxmAvuo0S+miNC1uAxtia4nwtN6tjM7xs6mvcM4nUmCu1J8 cHcrlDWl6He/7M0MtpxBDCojkIOJpXDGXB+SSeLlTFPl3HxulgrdwgxzYW6qSPMkxM JfRlbNwRUnhZ29gj8GkwJNTyshRRHCTOt1NiiTiI= Date: Mon, 10 Mar 2025 19:04:27 -0700 From: Andrew Morton To: Alexei Starovoitov Cc: bpf@vger.kernel.org, andrii@kernel.org, memxor@gmail.com, peterz@infradead.org, vbabka@suse.cz, bigeasy@linutronix.de, rostedt@goodmis.org, houtao1@huawei.com, hannes@cmpxchg.org, shakeel.butt@linux.dev, 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 v9 2/6] mm, bpf: Introduce try_alloc_pages() for opportunistic page allocation Message-Id: <20250310190427.32ce3ba9adb3771198fe2a5c@linux-foundation.org> In-Reply-To: <20250222024427.30294-3-alexei.starovoitov@gmail.com> References: <20250222024427.30294-1-alexei.starovoitov@gmail.com> <20250222024427.30294-3-alexei.starovoitov@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: E7BA380016 X-Stat-Signature: rycj51tw9wktjumdmqih8a388um43jrq X-Rspamd-Server: rspam09 X-HE-Tag: 1741658669-256955 X-HE-Meta: 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 iL4gjQ3B 4JlCBp9b7NQ++7up4L6ipLZidiK6K/oxcfAeho6R1hlnfvvhmDzgfoNabl+ysoAUEhH4EcSV271wWBLv3XRDiRwCqlXdespXpwX+A4gkTN2v6KMxjIjTBvntASUsmE5HCcBu89aCBREdxDv/TQi5qh4Z1uWaPY/Zydlpv3UhhkNp81pjMu5gtMkH1L9TCpA+vlOMqkDi49QBSeZ9U9kLNJUWvo6MHFbp/tbH4u6Ue7rO+Z3K8yA0LlW3xz4pLzq+m1mb8tFxn/Z5GAQ/V+WblFQDOct0FGmpJ6tkDvhkITWWSDnIzIIA3hqAjiuhYXEBoARCIua0rJSS6ZOLVRtCDQgqTXukhCLjZvNkg+Nhof/S0nbckTlVfjWctNmz5lECdph53F79wgX9MVgg= 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 Fri, 21 Feb 2025 18:44:23 -0800 Alexei Starovoitov wrote: > Tracing BPF programs execute from tracepoints and kprobes where > running context is unknown, but they need to request additional > memory. The prior workarounds were using pre-allocated memory and > BPF specific freelists to satisfy such allocation requests. The "prior workarounds" sound entirely appropriate. Because the performance and maintainability of Linux's page allocator is about 1,000,040 times more important than relieving BPF of having to carry a "workaround". IOW, I don't see any way in which this patchset even remotely meets any sane cost/benefit comparison. Feel free to explain why I am wrong, in great detail?