By default, the kernel btf that we load during loading program will be
freed after the programs are loaded in bpf_object_load(). However, we
still need to use these btf for tracing of multi-link during attaching.
Therefore, we don't free the btfs until the bpf object is closed if any
bpf programs of the type multi-link tracing exist.
Meanwhile, introduce the new api bpf_object__free_btf() to manually free
the btfs after attaching.
Signed-off-by: Menglong Dong <dongmenglong.8@bytedance.com>
---
tools/lib/bpf/libbpf.c | 47 ++++++++++++++++++++++++++++++----------
tools/lib/bpf/libbpf.h | 2 ++
tools/lib/bpf/libbpf.map | 1 +
3 files changed, 38 insertions(+), 12 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 567ad367e7aa..fd5428494a7e 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -8267,6 +8267,39 @@ static int bpf_object_prepare_struct_ops(struct bpf_object *obj)
return 0;
}
+void bpf_object__free_btfs(struct bpf_object *obj)
+{
+ int i;
+
+ /* clean up module BTFs */
+ for (i = 0; i < obj->btf_module_cnt; i++) {
+ close(obj->btf_modules[i].fd);
+ btf__free(obj->btf_modules[i].btf);
+ free(obj->btf_modules[i].name);
+ }
+ free(obj->btf_modules);
+ obj->btf_modules = NULL;
+ obj->btf_module_cnt = 0;
+
+ /* clean up vmlinux BTF */
+ btf__free(obj->btf_vmlinux);
+ obj->btf_vmlinux = NULL;
+}
+
+static void bpf_object_early_free_btf(struct bpf_object *obj)
+{
+ struct bpf_program *prog;
+
+ bpf_object__for_each_program(prog, obj) {
+ if (prog->expected_attach_type == BPF_TRACE_FENTRY_MULTI ||
+ prog->expected_attach_type == BPF_TRACE_FEXIT_MULTI ||
+ prog->expected_attach_type == BPF_MODIFY_RETURN_MULTI)
+ return;
+ }
+
+ bpf_object__free_btfs(obj);
+}
+
static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const char *target_btf_path)
{
int err, i;
@@ -8307,18 +8340,7 @@ static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const ch
/* clean up fd_array */
zfree(&obj->fd_array);
- /* clean up module BTFs */
- for (i = 0; i < obj->btf_module_cnt; i++) {
- close(obj->btf_modules[i].fd);
- btf__free(obj->btf_modules[i].btf);
- free(obj->btf_modules[i].name);
- }
- free(obj->btf_modules);
-
- /* clean up vmlinux BTF */
- btf__free(obj->btf_vmlinux);
- obj->btf_vmlinux = NULL;
-
+ bpf_object_early_free_btf(obj);
obj->loaded = true; /* doesn't matter if successfully or not */
if (err)
@@ -8791,6 +8813,7 @@ void bpf_object__close(struct bpf_object *obj)
usdt_manager_free(obj->usdt_man);
obj->usdt_man = NULL;
+ bpf_object__free_btfs(obj);
bpf_gen__free(obj->gen_loader);
bpf_object__elf_finish(obj);
bpf_object_unload(obj);
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 5723cbbfcc41..c41a909ea4c1 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -299,6 +299,8 @@ LIBBPF_API struct bpf_program *
bpf_object__find_program_by_name(const struct bpf_object *obj,
const char *name);
+LIBBPF_API void bpf_object__free_btfs(struct bpf_object *obj);
+
LIBBPF_API int
libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
enum bpf_attach_type *expected_attach_type);
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 86804fd90dd1..57642b78917f 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -413,4 +413,5 @@ LIBBPF_1.4.0 {
bpf_token_create;
btf__new_split;
btf_ext__raw_data;
+ bpf_object__free_btfs;
} LIBBPF_1.3.0;
--
2.39.2On Mon, Mar 11, 2024 at 2:35 AM Menglong Dong
<dongmenglong.8@bytedance.com> wrote:
>
> By default, the kernel btf that we load during loading program will be
> freed after the programs are loaded in bpf_object_load(). However, we
> still need to use these btf for tracing of multi-link during attaching.
> Therefore, we don't free the btfs until the bpf object is closed if any
> bpf programs of the type multi-link tracing exist.
>
> Meanwhile, introduce the new api bpf_object__free_btf() to manually free
> the btfs after attaching.
>
> Signed-off-by: Menglong Dong <dongmenglong.8@bytedance.com>
> ---
> tools/lib/bpf/libbpf.c | 47 ++++++++++++++++++++++++++++++----------
> tools/lib/bpf/libbpf.h | 2 ++
> tools/lib/bpf/libbpf.map | 1 +
> 3 files changed, 38 insertions(+), 12 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 567ad367e7aa..fd5428494a7e 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -8267,6 +8267,39 @@ static int bpf_object_prepare_struct_ops(struct bpf_object *obj)
> return 0;
> }
>
> +void bpf_object__free_btfs(struct bpf_object *obj)
> +{
> + int i;
> +
> + /* clean up module BTFs */
> + for (i = 0; i < obj->btf_module_cnt; i++) {
> + close(obj->btf_modules[i].fd);
> + btf__free(obj->btf_modules[i].btf);
> + free(obj->btf_modules[i].name);
> + }
> + free(obj->btf_modules);
> + obj->btf_modules = NULL;
> + obj->btf_module_cnt = 0;
> +
> + /* clean up vmlinux BTF */
> + btf__free(obj->btf_vmlinux);
> + obj->btf_vmlinux = NULL;
> +}
> +
> +static void bpf_object_early_free_btf(struct bpf_object *obj)
> +{
> + struct bpf_program *prog;
> +
> + bpf_object__for_each_program(prog, obj) {
> + if (prog->expected_attach_type == BPF_TRACE_FENTRY_MULTI ||
> + prog->expected_attach_type == BPF_TRACE_FEXIT_MULTI ||
> + prog->expected_attach_type == BPF_MODIFY_RETURN_MULTI)
> + return;
> + }
> +
> + bpf_object__free_btfs(obj);
> +}
> +
> static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const char *target_btf_path)
> {
> int err, i;
> @@ -8307,18 +8340,7 @@ static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const ch
> /* clean up fd_array */
> zfree(&obj->fd_array);
>
> - /* clean up module BTFs */
> - for (i = 0; i < obj->btf_module_cnt; i++) {
> - close(obj->btf_modules[i].fd);
> - btf__free(obj->btf_modules[i].btf);
> - free(obj->btf_modules[i].name);
> - }
> - free(obj->btf_modules);
> -
> - /* clean up vmlinux BTF */
> - btf__free(obj->btf_vmlinux);
> - obj->btf_vmlinux = NULL;
> -
> + bpf_object_early_free_btf(obj);
> obj->loaded = true; /* doesn't matter if successfully or not */
>
> if (err)
> @@ -8791,6 +8813,7 @@ void bpf_object__close(struct bpf_object *obj)
> usdt_manager_free(obj->usdt_man);
> obj->usdt_man = NULL;
>
> + bpf_object__free_btfs(obj);
> bpf_gen__free(obj->gen_loader);
> bpf_object__elf_finish(obj);
> bpf_object_unload(obj);
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 5723cbbfcc41..c41a909ea4c1 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -299,6 +299,8 @@ LIBBPF_API struct bpf_program *
> bpf_object__find_program_by_name(const struct bpf_object *obj,
> const char *name);
>
> +LIBBPF_API void bpf_object__free_btfs(struct bpf_object *obj);
> +
It shouldn't be exported.
libbpf should clean it up when bpf_object is freed.
On Tue, Mar 12, 2024 at 9:55 AM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Mon, Mar 11, 2024 at 2:35 AM Menglong Dong
> <dongmenglong.8@bytedance.com> wrote:
> >
> > By default, the kernel btf that we load during loading program will be
> > freed after the programs are loaded in bpf_object_load(). However, we
> > still need to use these btf for tracing of multi-link during attaching.
> > Therefore, we don't free the btfs until the bpf object is closed if any
> > bpf programs of the type multi-link tracing exist.
> >
> > Meanwhile, introduce the new api bpf_object__free_btf() to manually free
> > the btfs after attaching.
> >
> > Signed-off-by: Menglong Dong <dongmenglong.8@bytedance.com>
> > ---
> > tools/lib/bpf/libbpf.c | 47 ++++++++++++++++++++++++++++++----------
> > tools/lib/bpf/libbpf.h | 2 ++
> > tools/lib/bpf/libbpf.map | 1 +
> > 3 files changed, 38 insertions(+), 12 deletions(-)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 567ad367e7aa..fd5428494a7e 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -8267,6 +8267,39 @@ static int bpf_object_prepare_struct_ops(struct bpf_object *obj)
> > return 0;
> > }
> >
> > +void bpf_object__free_btfs(struct bpf_object *obj)
> > +{
> > + int i;
> > +
> > + /* clean up module BTFs */
> > + for (i = 0; i < obj->btf_module_cnt; i++) {
> > + close(obj->btf_modules[i].fd);
> > + btf__free(obj->btf_modules[i].btf);
> > + free(obj->btf_modules[i].name);
> > + }
> > + free(obj->btf_modules);
> > + obj->btf_modules = NULL;
> > + obj->btf_module_cnt = 0;
> > +
> > + /* clean up vmlinux BTF */
> > + btf__free(obj->btf_vmlinux);
> > + obj->btf_vmlinux = NULL;
> > +}
> > +
> > +static void bpf_object_early_free_btf(struct bpf_object *obj)
> > +{
> > + struct bpf_program *prog;
> > +
> > + bpf_object__for_each_program(prog, obj) {
> > + if (prog->expected_attach_type == BPF_TRACE_FENTRY_MULTI ||
> > + prog->expected_attach_type == BPF_TRACE_FEXIT_MULTI ||
> > + prog->expected_attach_type == BPF_MODIFY_RETURN_MULTI)
> > + return;
> > + }
> > +
> > + bpf_object__free_btfs(obj);
> > +}
> > +
> > static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const char *target_btf_path)
> > {
> > int err, i;
> > @@ -8307,18 +8340,7 @@ static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const ch
> > /* clean up fd_array */
> > zfree(&obj->fd_array);
> >
> > - /* clean up module BTFs */
> > - for (i = 0; i < obj->btf_module_cnt; i++) {
> > - close(obj->btf_modules[i].fd);
> > - btf__free(obj->btf_modules[i].btf);
> > - free(obj->btf_modules[i].name);
> > - }
> > - free(obj->btf_modules);
> > -
> > - /* clean up vmlinux BTF */
> > - btf__free(obj->btf_vmlinux);
> > - obj->btf_vmlinux = NULL;
> > -
> > + bpf_object_early_free_btf(obj);
> > obj->loaded = true; /* doesn't matter if successfully or not */
> >
> > if (err)
> > @@ -8791,6 +8813,7 @@ void bpf_object__close(struct bpf_object *obj)
> > usdt_manager_free(obj->usdt_man);
> > obj->usdt_man = NULL;
> >
> > + bpf_object__free_btfs(obj);
> > bpf_gen__free(obj->gen_loader);
> > bpf_object__elf_finish(obj);
> > bpf_object_unload(obj);
> > diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> > index 5723cbbfcc41..c41a909ea4c1 100644
> > --- a/tools/lib/bpf/libbpf.h
> > +++ b/tools/lib/bpf/libbpf.h
> > @@ -299,6 +299,8 @@ LIBBPF_API struct bpf_program *
> > bpf_object__find_program_by_name(const struct bpf_object *obj,
> > const char *name);
> >
> > +LIBBPF_API void bpf_object__free_btfs(struct bpf_object *obj);
> > +
>
> It shouldn't be exported.
> libbpf should clean it up when bpf_object is freed.
Yes, libbpf will clean up the btfs when bpf_object is freed in
this commit. And I'm trying to offer a way to early free the btfs
by the users manual to reduce the memory usage. Or, the
btfs that we opened will keep existing until we close the
bpf_object.
This is optional, I can remove it if you prefer.
Thanks!
Menglong Dong
On Mon, Mar 11, 2024 at 7:05 PM 梦龙董 <dongmenglong.8@bytedance.com> wrote: > > > > > > > +LIBBPF_API void bpf_object__free_btfs(struct bpf_object *obj); > > > + > > > > It shouldn't be exported. > > libbpf should clean it up when bpf_object is freed. > > Yes, libbpf will clean up the btfs when bpf_object is freed in > this commit. And I'm trying to offer a way to early free the btfs > by the users manual to reduce the memory usage. Or, the > btfs that we opened will keep existing until we close the > bpf_object. > > This is optional, I can remove it if you prefer. Let's not extend libbpf api unless we really need to. bpf_program__attach_trace_multi_opts() and *skel*__attach() can probably free them. I don't see a use case where you'd want to keep them afterwards.
On Tue, Mar 12, 2024 at 10:13 AM Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote: > > On Mon, Mar 11, 2024 at 7:05 PM 梦龙董 <dongmenglong.8@bytedance.com> wrote: > > > > > > > > > > +LIBBPF_API void bpf_object__free_btfs(struct bpf_object *obj); > > > > + > > > > > > It shouldn't be exported. > > > libbpf should clean it up when bpf_object is freed. > > > > Yes, libbpf will clean up the btfs when bpf_object is freed in > > this commit. And I'm trying to offer a way to early free the btfs > > by the users manual to reduce the memory usage. Or, the > > btfs that we opened will keep existing until we close the > > bpf_object. > > > > This is optional, I can remove it if you prefer. > > Let's not extend libbpf api unless we really need to. > bpf_program__attach_trace_multi_opts() and > *skel*__attach() can probably free them. That's a good idea! Should we add a "bool free_btf" field to struct bpf_trace_multi_opts? bpf_program__attach_trace_multi_opts() can be called multi times for a bpf_object, which has multi bpf program of type tracing multi-link. Or, can we free the btfs automatically if we found all tracing multi-link programs are attached? Thanks! Menglong Dong > I don't see a use case where you'd want to keep them afterwards.
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