Commit 8c3070e1 authored by Donglin Peng's avatar Donglin Peng Committed by Andrii Nakryiko
Browse files

btf: Optimize type lookup with binary search 



Improve btf_find_by_name_kind() performance by adding binary search
support for sorted types. Falls back to linear search for compatibility.

Signed-off-by: default avatarDonglin Peng <pengdonglin@xiaomi.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260109130003.3313716-7-dolinux.peng@gmail.com
parent 33ecca57

include/linux/btf.h

+1 −0
Original line number Diff line number Diff line
@@ -219,6 +219,7 @@ 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_named_start_id(const struct btf *btf, bool own);

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);

kernel/bpf/btf.c

+81 −9
Original line number Diff line number Diff line
@@ -259,6 +259,7 @@ struct btf { 
	void *nohdr_data;

	struct btf_header hdr;

	u32 nr_types; /* includes VOID for base BTF */

	u32 named_start_id;

	u32 types_size;

	u32 data_size;

	refcount_t refcnt;
@@ -494,6 +495,11 @@ 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;
@@ -544,21 +550,84 @@ u32 btf_nr_types(const struct btf *btf) 
	return total;

}



/*

 * btf_named_start_id - Get the named starting ID for the BTF

 * @btf: Pointer to the target BTF object

 * @own: Flag indicating whether to query only the current BTF (true = current BTF only,

 *       false = recursively traverse the base BTF chain)

 *

 * Return value rules:

 * 1. For a sorted btf, return its named_start_id

 * 2. Else for a split BTF, return its start_id

 * 3. Else for a base BTF, return 1

 */

u32 btf_named_start_id(const struct btf *btf, bool own)

{

	const struct btf *base_btf = btf;



	while (!own && base_btf->base_btf)

		base_btf = base_btf->base_btf;



	return base_btf->named_start_id ?: (base_btf->start_id ?: 1);

}



static s32 btf_find_by_name_kind_bsearch(const struct btf *btf, const char *name)

{

	const struct btf_type *t;

	const char *tname;

	s32 l, r, m;



	l = btf_named_start_id(btf, true);

	r = btf_nr_types(btf) - 1;

	while (l <= r) {

		m = l + (r - l) / 2;

		t = btf_type_by_id(btf, m);

		tname = btf_name_by_offset(btf, t->name_off);

		if (strcmp(tname, name) >= 0) {

			if (l == r)

				return r;

			r = m;

		} else {

			l = m + 1;

		}

	}



	return btf_nr_types(btf);

}



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;

	s32 id, total;



	if (base_btf) {

		id = btf_find_by_name_kind(base_btf, name, kind);

		if (id > 0)

			return id;

	}



	total = btf_nr_types(btf);

	for (i = 1; i < total; i++) {

		t = btf_type_by_id(btf, i);

	if (btf->named_start_id > 0 && name[0]) {

		id = btf_find_by_name_kind_bsearch(btf, name);

		for (; id < total; id++) {

			t = btf_type_by_id(btf, id);

			tname = btf_name_by_offset(btf, t->name_off);

			if (strcmp(tname, name) != 0)

				return -ENOENT;

			if (BTF_INFO_KIND(t->info) == kind)

				return id;

		}

	} else {

		for (id = btf_start_id(btf); id < total; id++) {

			t = btf_type_by_id(btf, id);

			if (BTF_INFO_KIND(t->info) != kind)

				continue;



			tname = btf_name_by_offset(btf, t->name_off);

		if (!strcmp(tname, name))

			return i;

			if (strcmp(tname, name) == 0)

				return id;

		}

	}



	return -ENOENT;
@@ -5791,6 +5860,7 @@ static struct btf *btf_parse(const union bpf_attr *attr, bpfptr_t uattr, u32 uat 
		goto errout;

	}

	env->btf = btf;

	btf->named_start_id = 0;



	data = kvmalloc(attr->btf_size, GFP_KERNEL | __GFP_NOWARN);

	if (!data) {
@@ -6210,6 +6280,7 @@ 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->named_start_id = 0;

	snprintf(btf->name, sizeof(btf->name), "%s", name);



	err = btf_parse_hdr(env);
@@ -6327,6 +6398,7 @@ 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->named_start_id = 0;

	snprintf(btf->name, sizeof(btf->name), "%s", module_name);



	btf->data = kvmemdup(data, data_size, GFP_KERNEL | __GFP_NOWARN);