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Tue, 16 Dec 2025 15:43:22 -0800 (PST) Message-ID: <9fbd1b7714fcd549d5d9c1aea47d50d93297ca26.camel@gmail.com> Subject: Re: [PATCH bpf-next v9 04/10] libbpf: Optimize type lookup with binary search for sorted BTF From: Eduard Zingerman To: Donglin Peng , ast@kernel.org, andrii.nakryiko@gmail.com Cc: zhangxiaoqin@xiaomi.com, ihor.solodrai@linux.dev, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, pengdonglin , Alan Maguire Date: Tue, 16 Dec 2025 15:43:19 -0800 In-Reply-To: References: <20251208062353.1702672-1-dolinux.peng@gmail.com> <20251208062353.1702672-5-dolinux.peng@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-2.fc42) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2025-12-16 at 15:38 -0800, Eduard Zingerman wrote: > On Mon, 2025-12-08 at 14:23 +0800, Donglin Peng wrote: >=20 > [...] >=20 > Lgtm, one question below. >=20 > > static __s32 btf_find_by_name_kind(const struct btf *btf, int start_id= , > > const char *type_name, __u32 kind) > > { > > - __u32 i, nr_types =3D btf__type_cnt(btf); > > + const struct btf_type *t; > > + const char *tname; > > + __s32 idx; > > + > > + if (start_id < btf->start_id) { > > + idx =3D btf_find_by_name_kind(btf->base_btf, start_id, > > + type_name, kind); > > + if (idx >=3D 0) > > + return idx; > > + start_id =3D btf->start_id; > > + } > > =20 > > - if (kind =3D=3D BTF_KIND_UNKN || !strcmp(type_name, "void")) > > + if (kind =3D=3D BTF_KIND_UNKN || strcmp(type_name, "void") =3D=3D 0) > > return 0; > > =20 > > - for (i =3D start_id; i < nr_types; i++) { > > - const struct btf_type *t =3D btf__type_by_id(btf, i); > > - const char *name; > > + if (btf->sorted_start_id > 0) { ^^^^^^^^^^^^^^^^^^^^^^^^ Also, previous implementation worked for anonymous types, but this one will not work because of the 'max(start_id, btf->sorted_start_id)', right? Maybe check that type is not anonymous in the condition above? > > + __s32 end_id =3D btf__type_cnt(btf) - 1; > > + > > + /* skip anonymous types */ > > + start_id =3D max(start_id, btf->sorted_start_id); > > + idx =3D btf_find_by_name_bsearch(btf, type_name, start_id, end_id); > > + if (unlikely(idx < 0)) > > + return libbpf_err(-ENOENT); > > + > > + if (unlikely(kind =3D=3D -1)) > > + return idx; > > + > > + t =3D btf_type_by_id(btf, idx); > > + if (likely(BTF_INFO_KIND(t->info) =3D=3D kind)) > > + return idx; > > + > > + for (idx++; idx <=3D end_id; idx++) { > > + t =3D btf__type_by_id(btf, idx); > > + tname =3D btf__str_by_offset(btf, t->name_off); > > + if (strcmp(tname, type_name) !=3D 0) > > + return libbpf_err(-ENOENT); > > + if (btf_kind(t) =3D=3D kind) > ^^^^^^^^^^^^^^^^^^^ > Is kind !=3D -1 check missing here? >=20 > > + return idx; > > + } > > + } else { > > + __u32 i, total; > > =20 > > - if (btf_kind(t) !=3D kind) > > - continue; > > - name =3D btf__name_by_offset(btf, t->name_off); > > - if (name && !strcmp(type_name, name)) > > - return i; > > + total =3D btf__type_cnt(btf); > > + for (i =3D start_id; i < total; i++) { > > + t =3D btf_type_by_id(btf, i); > > + if (kind !=3D -1 && btf_kind(t) !=3D kind) > > + continue; > > + tname =3D btf__str_by_offset(btf, t->name_off); > > + if (tname && strcmp(tname, type_name) =3D=3D 0) >=20 > Nit: no need for `tname &&` part, as we found out. >=20 > > + return i; > > + } > > } > > =20 > > return libbpf_err(-ENOENT); > > } > > =20 > > +/* the kind value of -1 indicates that kind matching should be skipped= */ > > +__s32 btf__find_by_name(const struct btf *btf, const char *type_name) > > +{ > > + return btf_find_by_name_kind(btf, btf->start_id, type_name, -1); > > +} > > + > > __s32 btf__find_by_name_kind_own(const struct btf *btf, const char *ty= pe_name, > > __u32 kind) > > { >=20 > [...]