Re: [PATCH v2 0/3] Use BPF filters for a "perf top -u" workaround

[Ian Rogers]

On Fri, May 24, 2024 at 10:58 AM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> On Wed, May 22, 2024 at 09:38:57PM -0700, Namhyung Kim wrote:
> > On Mon, May 20, 2024 at 6:04 PM Ian Rogers <irogers@xxxxxxxxxx> wrote:
> > >
> > > Allow uid and gid to be terms in BPF filters by first breaking the
> > > connection between filter terms and PERF_SAMPLE_xx values. Calculate
> > > the uid and gid using the bpf_get_current_uid_gid helper, rather than
> > > from a value in the sample. Allow filters to be passed to perf top, this allows:
> > >
> > > $ perf top -e cycles:P --filter "uid == $(id -u)"
> > >
> > > to work as a "perf top -u" workaround, as "perf top -u" usually fails
> > > due to processes/threads terminating between the /proc scan and the
> > > perf_event_open.
> > >
> > > v2. Allow PERF_SAMPLE_xx to be computed from the PBF_TERM_xx value
> > >     using a shift as requested by Namhyung.
> > >
> > > Ian Rogers (3):
> > >   perf bpf filter: Give terms their own enum
> > >   perf bpf filter: Add uid and gid terms
> > >   perf top: Allow filters on events
>
> Hmm.. I'm seeing this.
>
>   $ make build-test
>   ...
>   cd . && make GEN_VMLINUX_H=1 FEATURES_DUMP=/home/namhyung/project/linux/tools/perf/BUILD_TEST_FEATURE_DUMP -j64 O=/tmp/tmp.EeXFOfLPt5 DESTDIR=/tmp/tmp.Y0eiZKvc9D
>   ...
>     CLANG   /tmp/tmp.EeXFOfLPt5/util/bpf_skel/.tmp/sample_filter.bpf.o
>   In file included from util/bpf_skel/sample_filter.bpf.c:8:
>   In file included from util/bpf_skel/sample-filter.h:4:
>   /home/namhyung/project/linux/tools/include/uapi/linux/perf_event.h:29:6: error: redefinition of 'perf_type_id'
>   enum perf_type_id {
>        ^
>   /tmp/tmp.EeXFOfLPt5/util/bpf_skel/.tmp/../vmlinux.h:54086:6: note: previous definition is here
>   enum perf_type_id {
>        ^
>   In file included from util/bpf_skel/sample_filter.bpf.c:8:
>   In file included from util/bpf_skel/sample-filter.h:4:
>   /home/namhyung/project/linux/tools/include/uapi/linux/perf_event.h:30:2: error: redefinition of enumerator 'PERF_TYPE_HARDWARE'
>           PERF_TYPE_HARDWARE                      = 0,
>           ^
>   /tmp/tmp.EeXFOfLPt5/util/bpf_skel/.tmp/../vmlinux.h:54087:2: note: previous definition is here
>           PERF_TYPE_HARDWARE = 0,
>           ^
>   ...
>   make[3]: *** [Makefile.perf:264: sub-make] Error 2
>   make[2]: *** [Makefile:70: all] Error 2
>   make[1]: *** [tests/make:340: make_gen_vmlinux_h_O] Error 1
>   make: *** [Makefile:103: build-test] Error 2

IIRC this only exists for the sake of asserts. I can move the asserts
to placate the generated vmlinux.h. I'll send a v3.

Thanks,
Ian

> Thanks,
> Namhyung
>