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Thu, 06 Nov 2025 05:20:33 -0800 (PST) From: Donglin Peng To: ast@kernel.org Cc: eddyz87@gmail.com, andrii.nakryiko@gmail.com, zhangxiaoqin@xiaomi.com, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, Donglin Peng , Alan Maguire , Song Liu , Donglin Peng Subject: [PATCH v5 5/7] btf: Optimize type lookup with binary search Date: Thu, 6 Nov 2025 21:19:54 +0800 Message-Id: <20251106131956.1222864-6-dolinux.peng@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20251106131956.1222864-1-dolinux.peng@gmail.com> References: <20251106131956.1222864-1-dolinux.peng@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Donglin Peng Improve btf_find_by_name_kind() performance by adding binary search support for sorted types. Falls back to linear search for compatibility. Cc: Eduard Zingerman Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Alan Maguire Cc: Song Liu Cc: Xiaoqin Zhang Signed-off-by: Donglin Peng Signed-off-by: Donglin Peng --- kernel/bpf/btf.c | 117 +++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 107 insertions(+), 10 deletions(-) diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 0de8fc8a0e0b..66cb739a0598 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -192,6 +192,8 @@ */ #define BTF_MAX_SIZE (16 * 1024 * 1024) +#define BTF_NEED_SORT_CHECK ((u32)-1) + #define for_each_member_from(i, from, struct_type, member) \ for (i = from, member = btf_type_member(struct_type) + from; \ i < btf_type_vlen(struct_type); \ @@ -259,6 +261,7 @@ struct btf { void *nohdr_data; struct btf_header hdr; u32 nr_types; /* includes VOID for base BTF */ + u32 nr_sorted_types; /* exclude VOID for base BTF */ u32 types_size; u32 data_size; refcount_t refcnt; @@ -494,6 +497,11 @@ static bool btf_type_is_modifier(const struct btf_type *t) return false; } +static int btf_start_id(const struct btf *btf) +{ + return btf->start_id + (btf->base_btf ? 0 : 1); +} + bool btf_type_is_void(const struct btf_type *t) { return t == &btf_void; @@ -544,24 +552,110 @@ u32 btf_nr_types(const struct btf *btf) return total; } +/* Performs binary search within specified type ID range to find the leftmost + * BTF type matching the given name. The search assumes types are sorted by + * name in lexicographical order within the specified range. + * + * Return: Type ID of leftmost matching type, or -ENOENT if not found + */ +static s32 btf_find_by_name_kind_bsearch(const struct btf *btf, const char *name, + s32 start_id, s32 end_id) +{ + const struct btf_type *t; + const char *tname; + s32 l, r, m, lmost = -ENOENT; + int ret; + + l = start_id; + r = end_id; + while (l <= r) { + m = l + (r - l) / 2; + t = btf_type_by_id(btf, m); + tname = btf_name_by_offset(btf, t->name_off); + ret = strcmp(tname, name); + if (ret < 0) { + l = m + 1; + } else { + if (ret == 0) + lmost = m; + r = m - 1; + } + } + + return lmost; +} + +/* Searches for a BTF type with the specified name and kind. The function + * first recursively searches in the base BTF (if present), then searches + * in the current BTF using either binary search (if types are sorted) + * or linear search. + * + * Binary search is used when types are name-sorted (nr_sorted_types > 0). + * After finding a name match, it scans forward to find the first type + * that also matches the specified kind. Linear search is used for unsorted + * types, checking each type sequentially. + * + * Return: Type ID of matching type on success, -ENOENT if not found + */ s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind) { + const struct btf *base_btf = btf_base_btf(btf);; const struct btf_type *t; const char *tname; - u32 i, total; + int err = -ENOENT; - total = btf_nr_types(btf); - for (i = 1; i < total; i++) { - t = btf_type_by_id(btf, i); - if (BTF_INFO_KIND(t->info) != kind) - continue; + if (base_btf) { + err = btf_find_by_name_kind(base_btf, name, kind); + if (err > 0) + goto out; + } - tname = btf_name_by_offset(btf, t->name_off); - if (!strcmp(tname, name)) - return i; + if (btf->nr_sorted_types != BTF_NEED_SORT_CHECK) { + /* binary search */ + bool skip_first; + s32 start_id, end_id;; + int ret; + + start_id = btf_start_id(btf); + end_id = start_id + btf->nr_sorted_types - 1; + ret = btf_find_by_name_kind_bsearch(btf, name, start_id, end_id); + if (ret < 0) + goto out; + skip_first = true; + do { + t = btf_type_by_id(btf, ret); + if (BTF_INFO_KIND(t->info) != kind) { + if (skip_first) { + skip_first = false; + continue; + } + } else if (skip_first) { + return ret; + } + tname = btf_name_by_offset(btf, t->name_off); + if (!strcmp(tname, name)) + return ret; + else + break; + } while (++ret <= end_id); + } else { + /* linear search */ + u32 i, total; + + total = btf_nr_types(btf); + for (i = btf_start_id(btf); i < total; i++) { + t = btf_type_by_id(btf, i); + if (BTF_INFO_KIND(t->info) != kind) + continue; + + tname = btf_name_by_offset(btf, t->name_off); + if (!strcmp(tname, name)) + return i; + } } - return -ENOENT; +out: + return err; } s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p) @@ -5791,6 +5885,7 @@ static struct btf *btf_parse(const union bpf_attr *attr, bpfptr_t uattr, u32 uat goto errout; } env->btf = btf; + btf->nr_sorted_types = BTF_NEED_SORT_CHECK; data = kvmalloc(attr->btf_size, GFP_KERNEL | __GFP_NOWARN); if (!data) { @@ -6210,6 +6305,7 @@ static struct btf *btf_parse_base(struct btf_verifier_env *env, const char *name btf->data = data; btf->data_size = data_size; btf->kernel_btf = true; + btf->nr_sorted_types = BTF_NEED_SORT_CHECK; snprintf(btf->name, sizeof(btf->name), "%s", name); err = btf_parse_hdr(env); @@ -6327,6 +6423,7 @@ static struct btf *btf_parse_module(const char *module_name, const void *data, btf->start_id = base_btf->nr_types; btf->start_str_off = base_btf->hdr.str_len; btf->kernel_btf = true; + btf->nr_sorted_types = BTF_NEED_SORT_CHECK; snprintf(btf->name, sizeof(btf->name), "%s", module_name); btf->data = kvmemdup(data, data_size, GFP_KERNEL | __GFP_NOWARN); -- 2.34.1