The perf_event_cgrp_id can be different on other configurations.
To be more portable as CO-RE, it needs to get the cgroup subsys id
using the bpf_core_enum_value() helper.
Suggested-by: Ian Rogers <[email protected]>
Signed-off-by: Namhyung Kim <[email protected]>
---
v3 changes)
* check compiler features for enum value
v2 changes)
* fix off_cpu.bpf.c too
* get perf_subsys_id only once
tools/perf/util/bpf_skel/bperf_cgroup.bpf.c | 11 ++++++++++-
tools/perf/util/bpf_skel/off_cpu.bpf.c | 12 ++++++++----
2 files changed, 18 insertions(+), 5 deletions(-)
diff --git a/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c b/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
index 292c430768b5..8e7520e273db 100644
--- a/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
+++ b/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
@@ -48,6 +48,7 @@ const volatile __u32 num_cpus = 1;
int enabled = 0;
int use_cgroup_v2 = 0;
+int perf_subsys_id = -1;
static inline int get_cgroup_v1_idx(__u32 *cgrps, int size)
{
@@ -58,7 +59,15 @@ static inline int get_cgroup_v1_idx(__u32 *cgrps, int size)
int level;
int cnt;
- cgrp = BPF_CORE_READ(p, cgroups, subsys[perf_event_cgrp_id], cgroup);
+ if (perf_subsys_id == -1) {
+#if __has_builtin(__builtin_preserve_enum_value)
+ perf_subsys_id = bpf_core_enum_value(enum cgroup_subsys_id,
+ perf_event_cgrp_id);
+#else
+ perf_subsys_id = perf_event_cgrp_id;
+#endif
+ }
+ cgrp = BPF_CORE_READ(p, cgroups, subsys[perf_subsys_id], cgroup);
level = BPF_CORE_READ(cgrp, level);
for (cnt = 0; i < MAX_LEVELS; i++) {
diff --git a/tools/perf/util/bpf_skel/off_cpu.bpf.c b/tools/perf/util/bpf_skel/off_cpu.bpf.c
index c4ba2bcf179f..e917ef7b8875 100644
--- a/tools/perf/util/bpf_skel/off_cpu.bpf.c
+++ b/tools/perf/util/bpf_skel/off_cpu.bpf.c
@@ -94,6 +94,8 @@ const volatile bool has_prev_state = false;
const volatile bool needs_cgroup = false;
const volatile bool uses_cgroup_v1 = false;
+int perf_subsys_id = -1;
+
/*
* Old kernel used to call it task_struct->state and now it's '__state'.
* Use BPF CO-RE "ignored suffix rule" to deal with it like below:
@@ -119,11 +121,13 @@ static inline __u64 get_cgroup_id(struct task_struct *t)
{
struct cgroup *cgrp;
- if (uses_cgroup_v1)
- cgrp = BPF_CORE_READ(t, cgroups, subsys[perf_event_cgrp_id], cgroup);
- else
- cgrp = BPF_CORE_READ(t, cgroups, dfl_cgrp);
+ if (!uses_cgroup_v1)
+ return BPF_CORE_READ(t, cgroups, dfl_cgrp, kn, id);
+
+ if (perf_subsys_id == -1)
+ perf_subsys_id = bpf_core_enum_value(enum cgroup_subsys_id, perf_event_cgrp_id);
+ cgrp = BPF_CORE_READ(t, cgroups, subsys[perf_subsys_id], cgroup);
return BPF_CORE_READ(cgrp, kn, id);
}
--
2.37.3.998.g577e59143f-goog
On Thu, Sep 22, 2022 at 1:53 PM Namhyung Kim <[email protected]> wrote:
>
> The perf_event_cgrp_id can be different on other configurations.
> To be more portable as CO-RE, it needs to get the cgroup subsys id
> using the bpf_core_enum_value() helper.
>
> Suggested-by: Ian Rogers <[email protected]>
> Signed-off-by: Namhyung Kim <[email protected]>
> ---
> v3 changes)
> * check compiler features for enum value
>
> v2 changes)
> * fix off_cpu.bpf.c too
> * get perf_subsys_id only once
>
> tools/perf/util/bpf_skel/bperf_cgroup.bpf.c | 11 ++++++++++-
> tools/perf/util/bpf_skel/off_cpu.bpf.c | 12 ++++++++----
> 2 files changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c b/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
> index 292c430768b5..8e7520e273db 100644
> --- a/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
> +++ b/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
> @@ -48,6 +48,7 @@ const volatile __u32 num_cpus = 1;
>
> int enabled = 0;
> int use_cgroup_v2 = 0;
> +int perf_subsys_id = -1;
>
> static inline int get_cgroup_v1_idx(__u32 *cgrps, int size)
> {
> @@ -58,7 +59,15 @@ static inline int get_cgroup_v1_idx(__u32 *cgrps, int size)
> int level;
> int cnt;
>
> - cgrp = BPF_CORE_READ(p, cgroups, subsys[perf_event_cgrp_id], cgroup);
> + if (perf_subsys_id == -1) {
> +#if __has_builtin(__builtin_preserve_enum_value)
> + perf_subsys_id = bpf_core_enum_value(enum cgroup_subsys_id,
> + perf_event_cgrp_id);
> +#else
> + perf_subsys_id = perf_event_cgrp_id;
> +#endif
> + }
> + cgrp = BPF_CORE_READ(p, cgroups, subsys[perf_subsys_id], cgroup);
> level = BPF_CORE_READ(cgrp, level);
>
> for (cnt = 0; i < MAX_LEVELS; i++) {
> diff --git a/tools/perf/util/bpf_skel/off_cpu.bpf.c b/tools/perf/util/bpf_skel/off_cpu.bpf.c
> index c4ba2bcf179f..e917ef7b8875 100644
> --- a/tools/perf/util/bpf_skel/off_cpu.bpf.c
> +++ b/tools/perf/util/bpf_skel/off_cpu.bpf.c
> @@ -94,6 +94,8 @@ const volatile bool has_prev_state = false;
> const volatile bool needs_cgroup = false;
> const volatile bool uses_cgroup_v1 = false;
>
> +int perf_subsys_id = -1;
> +
> /*
> * Old kernel used to call it task_struct->state and now it's '__state'.
> * Use BPF CO-RE "ignored suffix rule" to deal with it like below:
> @@ -119,11 +121,13 @@ static inline __u64 get_cgroup_id(struct task_struct *t)
> {
> struct cgroup *cgrp;
>
> - if (uses_cgroup_v1)
> - cgrp = BPF_CORE_READ(t, cgroups, subsys[perf_event_cgrp_id], cgroup);
> - else
> - cgrp = BPF_CORE_READ(t, cgroups, dfl_cgrp);
> + if (!uses_cgroup_v1)
> + return BPF_CORE_READ(t, cgroups, dfl_cgrp, kn, id);
> +
> + if (perf_subsys_id == -1)
> + perf_subsys_id = bpf_core_enum_value(enum cgroup_subsys_id, perf_event_cgrp_id);
Should the "#if __has_builtin(__builtin_preserve_enum_value)" test also be here?
It feels a shame that bpf_core_enum_value isn't defined something like:
#if __has_builtin(__builtin_preserve_enum_value)
#define bpf_core_enum_value(enum_type, enum_value) \
__builtin_preserve_enum_value(*(typeof(enum_type) *)enum_value,
BPF_ENUMVAL_VALUE)
#else
#define bpf_core_enum_value(enum_type, enum_value) enum_value
#endif
for backward clang compatibility, but I could see why an error would
be preferable.
Thanks,
Ian
>
> + cgrp = BPF_CORE_READ(t, cgroups, subsys[perf_subsys_id], cgroup);
> return BPF_CORE_READ(cgrp, kn, id);
> }
>
> --
> 2.37.3.998.g577e59143f-goog
>
On Thu, Sep 22, 2022 at 4:55 PM Ian Rogers <[email protected]> wrote:
>
> On Thu, Sep 22, 2022 at 1:53 PM Namhyung Kim <[email protected]> wrote:
> >
> > The perf_event_cgrp_id can be different on other configurations.
> > To be more portable as CO-RE, it needs to get the cgroup subsys id
> > using the bpf_core_enum_value() helper.
> >
> > Suggested-by: Ian Rogers <[email protected]>
> > Signed-off-by: Namhyung Kim <[email protected]>
> > ---
> > v3 changes)
> > * check compiler features for enum value
> >
> > v2 changes)
> > * fix off_cpu.bpf.c too
> > * get perf_subsys_id only once
> >
> > tools/perf/util/bpf_skel/bperf_cgroup.bpf.c | 11 ++++++++++-
> > tools/perf/util/bpf_skel/off_cpu.bpf.c | 12 ++++++++----
> > 2 files changed, 18 insertions(+), 5 deletions(-)
> >
> > diff --git a/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c b/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
> > index 292c430768b5..8e7520e273db 100644
> > --- a/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
> > +++ b/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
> > @@ -48,6 +48,7 @@ const volatile __u32 num_cpus = 1;
> >
> > int enabled = 0;
> > int use_cgroup_v2 = 0;
> > +int perf_subsys_id = -1;
> >
> > static inline int get_cgroup_v1_idx(__u32 *cgrps, int size)
> > {
> > @@ -58,7 +59,15 @@ static inline int get_cgroup_v1_idx(__u32 *cgrps, int size)
> > int level;
> > int cnt;
> >
> > - cgrp = BPF_CORE_READ(p, cgroups, subsys[perf_event_cgrp_id], cgroup);
> > + if (perf_subsys_id == -1) {
> > +#if __has_builtin(__builtin_preserve_enum_value)
> > + perf_subsys_id = bpf_core_enum_value(enum cgroup_subsys_id,
> > + perf_event_cgrp_id);
> > +#else
> > + perf_subsys_id = perf_event_cgrp_id;
> > +#endif
> > + }
> > + cgrp = BPF_CORE_READ(p, cgroups, subsys[perf_subsys_id], cgroup);
> > level = BPF_CORE_READ(cgrp, level);
> >
> > for (cnt = 0; i < MAX_LEVELS; i++) {
> > diff --git a/tools/perf/util/bpf_skel/off_cpu.bpf.c b/tools/perf/util/bpf_skel/off_cpu.bpf.c
> > index c4ba2bcf179f..e917ef7b8875 100644
> > --- a/tools/perf/util/bpf_skel/off_cpu.bpf.c
> > +++ b/tools/perf/util/bpf_skel/off_cpu.bpf.c
> > @@ -94,6 +94,8 @@ const volatile bool has_prev_state = false;
> > const volatile bool needs_cgroup = false;
> > const volatile bool uses_cgroup_v1 = false;
> >
> > +int perf_subsys_id = -1;
> > +
> > /*
> > * Old kernel used to call it task_struct->state and now it's '__state'.
> > * Use BPF CO-RE "ignored suffix rule" to deal with it like below:
> > @@ -119,11 +121,13 @@ static inline __u64 get_cgroup_id(struct task_struct *t)
> > {
> > struct cgroup *cgrp;
> >
> > - if (uses_cgroup_v1)
> > - cgrp = BPF_CORE_READ(t, cgroups, subsys[perf_event_cgrp_id], cgroup);
> > - else
> > - cgrp = BPF_CORE_READ(t, cgroups, dfl_cgrp);
> > + if (!uses_cgroup_v1)
> > + return BPF_CORE_READ(t, cgroups, dfl_cgrp, kn, id);
> > +
> > + if (perf_subsys_id == -1)
> > + perf_subsys_id = bpf_core_enum_value(enum cgroup_subsys_id, perf_event_cgrp_id);
>
> Should the "#if __has_builtin(__builtin_preserve_enum_value)" test also be here?
Ouch! Will send v4.
>
> It feels a shame that bpf_core_enum_value isn't defined something like:
>
> #if __has_builtin(__builtin_preserve_enum_value)
> #define bpf_core_enum_value(enum_type, enum_value) \
> __builtin_preserve_enum_value(*(typeof(enum_type) *)enum_value,
> BPF_ENUMVAL_VALUE)
> #else
> #define bpf_core_enum_value(enum_type, enum_value) enum_value
> #endif
Yeah, that would be much easier to use.
Thanks,
Namhyung
>
> for backward clang compatibility, but I could see why an error would
> be preferable.
>
> Thanks,
> Ian
>
> >
> > + cgrp = BPF_CORE_READ(t, cgroups, subsys[perf_subsys_id], cgroup);
> > return BPF_CORE_READ(cgrp, kn, id);
> > }
> >
> > --
> > 2.37.3.998.g577e59143f-goog
> >