From: Donglin Peng <pengdonglin@xiaomi.com>
This patch introduces binary search optimization for BTF type lookups
when the BTF instance contains sorted types.
The optimization significantly improves performance when searching for
types in large BTF instances with sorted types. For unsorted BTF, the
implementation falls back to the original linear search.
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: Donglin Peng <pengdonglin@xiaomi.com>
---
tools/lib/bpf/btf.c | 90 +++++++++++++++++++++++++++++++++------------
1 file changed, 66 insertions(+), 24 deletions(-)
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index bf75f770d29a..60ff8eafea83 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -92,6 +92,8 @@ struct btf {
* - for split BTF counts number of types added on top of base BTF.
*/
__u32 nr_types;
+ /* the start IDs of named types in sorted BTF */
+ int named_start_id;
/* if not NULL, points to the base BTF on top of which the current
* split BTF is based
*/
@@ -897,46 +899,83 @@ int btf__resolve_type(const struct btf *btf, __u32 type_id)
return type_id;
}
-__s32 btf__find_by_name(const struct btf *btf, const char *type_name)
+static __s32 btf_find_type_by_name_bsearch(const struct btf *btf, const char *name,
+ __s32 start_id)
{
- __u32 i, nr_types = btf__type_cnt(btf);
-
- if (!strcmp(type_name, "void"))
- return 0;
-
- for (i = 1; i < nr_types; i++) {
- const struct btf_type *t = btf__type_by_id(btf, i);
- const char *name = btf__name_by_offset(btf, t->name_off);
-
- if (name && !strcmp(type_name, name))
- return i;
+ const struct btf_type *t;
+ const char *tname;
+ __s32 l, r, m;
+
+ l = start_id;
+ r = btf__type_cnt(btf) - 1;
+ while (l <= r) {
+ m = l + (r - l) / 2;
+ t = btf_type_by_id(btf, m);
+ tname = btf__str_by_offset(btf, t->name_off);
+ if (strcmp(tname, name) >= 0) {
+ if (l == r)
+ return r;
+ r = m;
+ } else {
+ l = m + 1;
+ }
}
- return libbpf_err(-ENOENT);
+ return btf__type_cnt(btf);
}
static __s32 btf_find_by_name_kind(const struct btf *btf, int start_id,
- const char *type_name, __u32 kind)
+ const char *type_name, __s32 kind)
{
- __u32 i, nr_types = btf__type_cnt(btf);
+ const struct btf_type *t;
+ const char *tname;
+ __s32 idx;
+
+ if (start_id < btf->start_id) {
+ idx = btf_find_by_name_kind(btf->base_btf, start_id,
+ type_name, kind);
+ if (idx >= 0)
+ return idx;
+ start_id = btf->start_id;
+ }
- if (kind == BTF_KIND_UNKN || !strcmp(type_name, "void"))
+ if (kind == BTF_KIND_UNKN || strcmp(type_name, "void") == 0)
return 0;
- for (i = start_id; i < nr_types; i++) {
- const struct btf_type *t = btf__type_by_id(btf, i);
- const char *name;
+ if (btf->named_start_id > 0 && type_name[0]) {
+ start_id = max(start_id, btf->named_start_id);
+ idx = btf_find_type_by_name_bsearch(btf, type_name, start_id);
+ for (; idx < btf__type_cnt(btf); idx++) {
+ t = btf__type_by_id(btf, idx);
+ tname = btf__str_by_offset(btf, t->name_off);
+ if (strcmp(tname, type_name) != 0)
+ return libbpf_err(-ENOENT);
+ if (kind < 0 || btf_kind(t) == kind)
+ return idx;
+ }
+ } else {
+ __u32 i, total;
- if (btf_kind(t) != kind)
- continue;
- name = btf__name_by_offset(btf, t->name_off);
- if (name && !strcmp(type_name, name))
- return i;
+ total = btf__type_cnt(btf);
+ for (i = start_id; i < total; i++) {
+ t = btf_type_by_id(btf, i);
+ if (kind > 0 && btf_kind(t) != kind)
+ continue;
+ tname = btf__str_by_offset(btf, t->name_off);
+ if (strcmp(tname, type_name) == 0)
+ return i;
+ }
}
return libbpf_err(-ENOENT);
}
+/* 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 *type_name,
__u32 kind)
{
@@ -1006,6 +1045,7 @@ static struct btf *btf_new_empty(struct btf *base_btf)
btf->fd = -1;
btf->ptr_sz = sizeof(void *);
btf->swapped_endian = false;
+ btf->named_start_id = 0;
if (base_btf) {
btf->base_btf = base_btf;
@@ -1057,6 +1097,7 @@ static struct btf *btf_new(const void *data, __u32 size, struct btf *base_btf, b
btf->start_id = 1;
btf->start_str_off = 0;
btf->fd = -1;
+ btf->named_start_id = 0;
if (base_btf) {
btf->base_btf = base_btf;
@@ -1715,6 +1756,7 @@ static void btf_invalidate_raw_data(struct btf *btf)
free(btf->raw_data_swapped);
btf->raw_data_swapped = NULL;
}
+ btf->named_start_id = 0;
}
/* Ensure BTF is ready to be modified (by splitting into a three memory
--
2.34.1> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> index bf75f770d29a..60ff8eafea83 100644
> --- a/tools/lib/bpf/btf.c
> +++ b/tools/lib/bpf/btf.c
[ ... ]
> @@ -897,46 +899,83 @@ int btf__resolve_type(const struct btf *btf, __u32 type_id)
> return type_id;
> }
>
> -__s32 btf__find_by_name(const struct btf *btf, const char *type_name)
> -{
> - __u32 i, nr_types = btf__type_cnt(btf);
> -
> - if (!strcmp(type_name, "void"))
> - return 0;
> -
> - for (i = 1; i < nr_types; i++) {
^
The original btf__find_by_name() started iteration from ID 1, which meant
it would search through ALL types including those in base BTF for split
BTF scenarios. The btf__type_by_id() call would transparently access
base BTF types when i < btf->start_id.
> - const struct btf_type *t = btf__type_by_id(btf, i);
> - const char *name = btf__name_by_offset(btf, t->name_off);
> -
> - if (name && !strcmp(type_name, name))
> - return i;
> - }
> -
> - return libbpf_err(-ENOENT);
> -}
[ ... ]
> +/* 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);
^^^^^^^^^^^^^^^
Is this intended to change the split BTF lookup behavior? The new
implementation passes btf->start_id as the start_id parameter, which
means for split BTF the search will only cover types in the current BTF
instance, not the base BTF.
In btf_find_by_name_kind(), the base BTF is only searched when
start_id < btf->start_id, but here start_id == btf->start_id so that
condition is never true.
Compare with btf__find_by_name_kind() which still passes 1 as start_id:
__s32 btf__find_by_name_kind(const struct btf *btf, ...)
{
return btf_find_by_name_kind(btf, 1, type_name, kind);
}
This creates an inconsistency where btf__find_by_name_kind() searches
base BTF but btf__find_by_name() does not. Was this behavior change
intentional? If so, perhaps the commit message should mention it.
> +}
> +
> __s32 btf__find_by_name_kind_own(const struct btf *btf, const char *type_name,
> __u32 kind)
> {
> return btf_find_by_name_kind(btf, btf->start_id, type_name, kind);
> }
[ ... ]
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/20804442135
On Thu, Jan 8, 2026 at 11:46 AM <bot+bpf-ci@kernel.org> wrote:
>
> > diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> > index bf75f770d29a..60ff8eafea83 100644
> > --- a/tools/lib/bpf/btf.c
> > +++ b/tools/lib/bpf/btf.c
>
> [ ... ]
>
> > @@ -897,46 +899,83 @@ int btf__resolve_type(const struct btf *btf, __u32 type_id)
> > return type_id;
> > }
> >
> > -__s32 btf__find_by_name(const struct btf *btf, const char *type_name)
> > -{
> > - __u32 i, nr_types = btf__type_cnt(btf);
> > -
> > - if (!strcmp(type_name, "void"))
> > - return 0;
> > -
> > - for (i = 1; i < nr_types; i++) {
> ^
> The original btf__find_by_name() started iteration from ID 1, which meant
> it would search through ALL types including those in base BTF for split
> BTF scenarios. The btf__type_by_id() call would transparently access
> base BTF types when i < btf->start_id.
>
> > - const struct btf_type *t = btf__type_by_id(btf, i);
> > - const char *name = btf__name_by_offset(btf, t->name_off);
> > -
> > - if (name && !strcmp(type_name, name))
> > - return i;
> > - }
> > -
> > - return libbpf_err(-ENOENT);
> > -}
>
> [ ... ]
>
> > +/* 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);
> ^^^^^^^^^^^^^^^
> Is this intended to change the split BTF lookup behavior? The new
Thanks, my bad. We should pass 1, not btf->start_id.
> implementation passes btf->start_id as the start_id parameter, which
> means for split BTF the search will only cover types in the current BTF
> instance, not the base BTF.
>
> In btf_find_by_name_kind(), the base BTF is only searched when
> start_id < btf->start_id, but here start_id == btf->start_id so that
> condition is never true.
>
> Compare with btf__find_by_name_kind() which still passes 1 as start_id:
>
> __s32 btf__find_by_name_kind(const struct btf *btf, ...)
> {
> return btf_find_by_name_kind(btf, 1, type_name, kind);
> }
>
> This creates an inconsistency where btf__find_by_name_kind() searches
> base BTF but btf__find_by_name() does not. Was this behavior change
> intentional? If so, perhaps the commit message should mention it.
>
> > +}
> > +
> > __s32 btf__find_by_name_kind_own(const struct btf *btf, const char *type_name,
> > __u32 kind)
> > {
> > return btf_find_by_name_kind(btf, btf->start_id, type_name, kind);
> > }
>
> [ ... ]
>
>
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
>
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/20804442135
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