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Wed, 16 Sep 2026 18:56:10 -0700 (PDT) Received: from localhost ([153.61.198.253]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39e390c2984sm387496a91.0.2026.09.16.18.56.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Sep 2026 18:56:10 -0700 (PDT) Content-Type: text/plain; charset=UTF-8 Date: Thu, 17 Sep 2026 01:56:09 +0000 Message-Id: Cc: , , , , , , , , , , Subject: Re: [PATCH bpf-next 1/1] bpf: btf: add btf=off boot parameter to disable and free vmlinux BTF From: "Alexei Starovoitov" To: "Jay Wang" , , , In-Reply-To: <20260917000201.25581-2-wanjay@amazon.com> References: <20260917000201.25581-1-wanjay@amazon.com> <20260917000201.25581-2-wanjay@amazon.com> X-Mailer: mkdraft (claude review draft; edit before sending) Content-Transfer-Encoding: 8bit MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260916_185612_420589_66726012 X-CRM114-Status: GOOD ( 11.95 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Sep 17, 2026 at 12:02 AM Jay Wang wrote: > > Add a "btf=off" early boot parameter, similar to the existing "selinux=0" > parameter, so users who do not want BTF can turn it off at boot; the > section is then freed to save memory. tbh I'm not excited about btf=off. BTF is not debug info anymore. sched_ext, bpf-lsm (systemd uses it), hid-bpf, most of bcc/bpftrace quietly stop working, and we'll be the ones triaging "libbpf: failed to find valid kernel BTF" reports from people who copy-pasted a "save 5MB" tuning guide. This needs more thought. > .../admin-guide/kernel-parameters.txt | 14 +++ > arch/arm64/mm/mmu.c | 108 +++++++++++++++++- > arch/x86/mm/init_64.c | 30 +++++ > arch/x86/mm/pat/set_memory.c | 28 ++++- > include/linux/btf.h | 9 ++ > kernel/bpf/btf.c | 51 ++++++++- > kernel/bpf/sysfs_btf.c | 7 ++ > kernel/bpf/verifier.c | 2 +- This doesn't apply to bpf-next. Consider using Alan's approach and support CONFIG_DEBUG_INFO_BTF=m pw-bot: cr