[RFC bpf-next v8 8/9] bpf: Optimize the performance of find_btf_percpu_datasec

[Donglin Peng <dolinux.peng@gmail.com>]

From: pengdonglin <pengdonglin@xiaomi.com>

Currently, vmlinux and kernel module BTFs are unconditionally
sorted during the build phase, with named types placed at the
end. Thus, anonymous types should be skipped when starting the
search. In my vmlinux BTF, the number of anonymous types is
61,747, which means the loop count can be reduced by 61,747.

Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Alan Maguire <alan.maguire@oracle.com>
Cc: Ihor Solodrai <ihor.solodrai@linux.dev>
Cc: Xiaoqin Zhang <zhangxiaoqin@xiaomi.com>
Signed-off-by: pengdonglin <pengdonglin@xiaomi.com>
---
 include/linux/btf.h   | 1 +
 kernel/bpf/btf.c      | 5 +++++
 kernel/bpf/verifier.c | 7 +------
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index f06976ffb63f..2d28f2b22ae5 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -220,6 +220,7 @@ bool btf_is_module(const struct btf *btf);
 bool btf_is_vmlinux(const struct btf *btf);
 struct module *btf_try_get_module(const struct btf *btf);
 u32 btf_nr_types(const struct btf *btf);
+u32 btf_sorted_start_id(const struct btf *btf);
 struct btf *btf_base_btf(const struct btf *btf);
 bool btf_type_is_i32(const struct btf_type *t);
 bool btf_type_is_i64(const struct btf_type *t);
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 925cb524f3a8..205b9c3bf194 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -550,6 +550,11 @@ u32 btf_nr_types(const struct btf *btf)
 	return total;
 }
 
+u32 btf_sorted_start_id(const struct btf *btf)
+{
+	return btf->sorted_start_id ?: (btf->start_id ?: 1);
+}
+
 /*
  * Assuming that types are sorted by name in ascending order.
  */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 10d24073c692..367699591fb0 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -20576,12 +20576,7 @@ static int find_btf_percpu_datasec(struct btf *btf)
 	 * types to look at only module's own BTF types.
 	 */
 	n = btf_nr_types(btf);
-	if (btf_is_module(btf))
-		i = btf_nr_types(btf_vmlinux);
-	else
-		i = 1;
-
-	for(; i < n; i++) {
+	for (i = btf_sorted_start_id(btf); i < n; i++) {
 		t = btf_type_by_id(btf, i);
 		if (BTF_INFO_KIND(t->info) != BTF_KIND_DATASEC)
 			continue;
-- 
2.34.1