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Mon, 19 Jan 2026 18:32:59 -0800 (PST) From: Qiliang Yuan To: alexei.starovoitov@gmail.com, eddyz87@gmail.com Cc: andrii.nakryiko@gmail.com, andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org, daniel@iogearbox.net, haoluo@google.com, jolsa@kernel.org, kpsingh@kernel.org, linux-kernel@vger.kernel.org, martin.lau@linux.dev, realwujing@gmail.com, sdf@fomichev.me, song@kernel.org, yonghong.song@linux.dev Subject: [PATCH v4] bpf/verifier: optimize ID mapping reset in states_equal Date: Tue, 20 Jan 2026 10:32:34 +0800 Message-Id: <20260120023234.77673-1-realwujing@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Currently, reset_idmap_scratch() performs a 4.7KB memset() in every states_equal() call. Optimize this by using a counter to track used ID mappings, replacing the O(N) memset() with an O(1) reset and bounding the search loop in check_ids(). Acked-by: Eduard Zingerman Signed-off-by: Qiliang Yuan --- include/linux/bpf_verifier.h | 1 + kernel/bpf/verifier.c | 23 ++++++++++++++--------- 2 files changed, 15 insertions(+), 9 deletions(-) diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 130bcbd66f60..8355b585cd18 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -692,6 +692,7 @@ struct bpf_id_pair { =20 struct bpf_idmap { u32 tmp_id_gen; + u32 cnt; struct bpf_id_pair map[BPF_ID_MAP_SIZE]; }; =20 diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 3135643d5695..6ec6d70e5ce7 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -18948,18 +18948,21 @@ static bool check_ids(u32 old_id, u32 cur_id, str= uct bpf_idmap *idmap) if (old_id =3D=3D 0) /* cur_id =3D=3D 0 as well */ return true; =20 - for (i =3D 0; i < BPF_ID_MAP_SIZE; i++) { - if (!map[i].old) { - /* Reached an empty slot; haven't seen this id before */ - map[i].old =3D old_id; - map[i].cur =3D cur_id; - return true; - } + for (i =3D 0; i < idmap->cnt; i++) { if (map[i].old =3D=3D old_id) return map[i].cur =3D=3D cur_id; if (map[i].cur =3D=3D cur_id) return false; } + + /* Reached the end of known mappings; haven't seen this id before */ + if (idmap->cnt < BPF_ID_MAP_SIZE) { + map[idmap->cnt].old =3D old_id; + map[idmap->cnt].cur =3D cur_id; + idmap->cnt++; + return true; + } + /* We ran out of idmap slots, which should be impossible */ WARN_ON_ONCE(1); return false; @@ -19470,8 +19473,10 @@ static bool func_states_equal(struct bpf_verifier_= env *env, struct bpf_func_stat =20 static void reset_idmap_scratch(struct bpf_verifier_env *env) { - env->idmap_scratch.tmp_id_gen =3D env->id_gen; - memset(&env->idmap_scratch.map, 0, sizeof(env->idmap_scratch.map)); + struct bpf_idmap *idmap =3D &env->idmap_scratch; + + idmap->tmp_id_gen =3D env->id_gen; + idmap->cnt =3D 0; } =20 static bool states_equal(struct bpf_verifier_env *env, --=20 2.39.5