| Message ID | 20220922044023.718774-1-namhyung@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | [v2] perf tools: Get a perf cgroup more portably in BPF | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
Em Wed, Sep 21, 2022 at 09:40:23PM -0700, Namhyung Kim escreveu: > 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 <irogers@google.com> > Signed-off-by: Namhyung Kim <namhyung@kernel.org> Applying, Ian, can I have your Reviewed-by? - Arnaldo > --- > v2 changes) > * fix off_cpu.bpf.c too > * get perf_subsys_id only once > > tools/perf/util/bpf_skel/bperf_cgroup.bpf.c | 6 +++++- > tools/perf/util/bpf_skel/off_cpu.bpf.c | 12 ++++++++---- > 2 files changed, 13 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..9223e4b87fe9 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 +59,10 @@ 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) > + perf_subsys_id = bpf_core_enum_value(enum cgroup_subsys_id, perf_event_cgrp_id); > + > + 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); > } > > -- > 2.37.3.968.ga6b4b080e4-goog
On Wed, Sep 21, 2022 at 9:40 PM Namhyung Kim <namhyung@kernel.org> 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. > I remember using bpf_core_enum_value requires a compiler built-in. So the build will fail on old compiler such as clang-11. See [1]. Maybe we should surround it with #if __has_builtin(__builtin_preserve_enum_value) to be sure. [1] https://www.spinics.net/lists/bpf/msg30859.html > Suggested-by: Ian Rogers <irogers@google.com> > Signed-off-by: Namhyung Kim <namhyung@kernel.org> > --- [...]
Hi Hao, On Thu, Sep 22, 2022 at 12:36 PM Hao Luo <haoluo@google.com> wrote: > > On Wed, Sep 21, 2022 at 9:40 PM Namhyung Kim <namhyung@kernel.org> 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. > > > > I remember using bpf_core_enum_value requires a compiler built-in. So > the build will fail on old compiler such as clang-11. See [1]. Maybe > we should surround it with #if > __has_builtin(__builtin_preserve_enum_value) to be sure. > > [1] https://www.spinics.net/lists/bpf/msg30859.html Thanks for pointing this out. As this is a kind of optimization I think we can fallback to using the existing value if not available. Will send v3. Thanks, Namhyung
diff --git a/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c b/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c index 292c430768b5..9223e4b87fe9 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 +59,10 @@ 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) + perf_subsys_id = bpf_core_enum_value(enum cgroup_subsys_id, perf_event_cgrp_id); + + 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); }
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 <irogers@google.com> Signed-off-by: Namhyung Kim <namhyung@kernel.org> --- v2 changes) * fix off_cpu.bpf.c too * get perf_subsys_id only once tools/perf/util/bpf_skel/bperf_cgroup.bpf.c | 6 +++++- tools/perf/util/bpf_skel/off_cpu.bpf.c | 12 ++++++++---- 2 files changed, 13 insertions(+), 5 deletions(-)