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([2620:10d:c092:500::4:5d16]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43970bf9f6csm21443781f8f.7.2026.02.23.05.57.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Feb 2026 05:57:32 -0800 (PST) Message-ID: <260229af-3ea8-43c3-bfd7-fe6b3471e75d@gmail.com> Date: Mon, 23 Feb 2026 13:57:31 +0000 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next v2 0/2] libbpf: Add bpf_program__clone() for individual program loading To: Alexei Starovoitov Cc: bpf , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin Lau , Kernel Team , Eduard , Mykyta Yatsenko References: <20260220-veristat_prepare-v2-0-15bff49022a7@meta.com> Content-Language: en-US From: Mykyta Yatsenko In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2/20/26 22:48, Alexei Starovoitov wrote: > On Fri, Feb 20, 2026 at 11:18 AM Mykyta Yatsenko > wrote: >> This series adds bpf_program__clone() to libbpf and converts veristat to >> use it, replacing the costly per-program object re-opening pattern. >> >> veristat needs to load each BPF program in isolation to collect >> per-program verification statistics. Previously it achieved this by >> opening a fresh bpf_object for every program, disabling autoload on all >> but the target, and loading the whole object. For object files with many >> programs this meant repeating ELF parsing and BTF processing N times. >> >> Patch 1 introduces bpf_program__clone(), which loads a single program >> from a prepared object into the kernel and returns an fd owned by the >> caller. It resolves BTF attach targets, fills in func/line info, >> fd_array, and other load parameters from the prepared object >> automatically, while letting callers override any field via >> bpf_prog_load_opts. >> >> Patch 2 converts veristat to prepare the object once and clone each >> program individually, eliminating redundant work. >> >> Performance >> Tested on selftests: 918 objects, ~4270 programs: >> - Wall time: 36.88s -> 23.18s (37% faster) >> - User time: 20.80s -> 16.07s (23% faster) >> - Kernel time: 12.07s -> 6.06s (50% faster) >> >> Per-program loading also improves coverage: 83 programs that previously >> failed now succeed. > Wait what? How is that possible? Thanks for asking. Take for example verifier_unpriv.bpf.o object, all progs fail to load on the system veristat, the errors are: ``` libbpf: map 'map_prog1_socket': failed to initialize slot [1] to prog 'dummy_prog_loop1_socket' fd=-2: -EBADF ... libbpf: map 'map_prog1_socket': failed to initialize slot [0] to prog 'dummy_prog_42_socket' fd=-2: -EBADF ... etc ``` I understand this is due to the libbpf trying to initialize all PROG_ARRAY maps during object load, regardless if the corresponding program is loading or not (currently only 1 program is enabled at a time, so object that has those PROG_ARRAY has no chance to succeed) This root cause is the only reason for all 83 improvements. This is not intentional, but it sounds like a nice side-effect, so I mention it. Is this something we would like to address in libbpf?