netdev - Re: [PATCH bpf-next v5 2/2] samples: bpf: refactor perf_event user program with libbpf bpf

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Date:   Sun, 22 Mar 2020 08:03:59 +0900
From:   "Daniel T. Lee" <danieltimlee@...il.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v5 2/2] samples: bpf: refactor perf_event user
 program with libbpf bpf_link

Thank you for your time and effort for the review :)

Best,
Daniel

On Sun, Mar 22, 2020 at 4:43 AM Andrii Nakryiko
<andrii.nakryiko@...il.com> wrote:
>
> On Sat, Mar 21, 2020 at 3:04 AM Daniel T. Lee <danieltimlee@...il.com> wrote:
> >
> > The bpf_program__attach of libbpf(using bpf_link) is much more intuitive
> > than the previous method using ioctl.
> >
> > bpf_program__attach_perf_event manages the enable of perf_event and
> > attach of BPF programs to it, so there's no neeed to do this
> > directly with ioctl.
> >
> > In addition, bpf_link provides consistency in the use of API because it
> > allows disable (detach, destroy) for multiple events to be treated as
> > one bpf_link__destroy. Also, bpf_link__destroy manages the close() of
> > perf_event fd.
> >
> > This commit refactors samples that attach the bpf program to perf_event
> > by using libbbpf instead of ioctl. Also the bpf_load in the samples were
> > removed and migrated to use libbbpf API.
> >
> > Signed-off-by: Daniel T. Lee <danieltimlee@...il.com>
> >
> > ---
>
> LGTM.
>
> Acked-by: Andrii Nakryiko <andriin@...com>
>
> > Changes in v2:
> >  - check memory allocation is successful
> >  - clean up allocated memory on error
> >
> > Changes in v3:
> >  - Improve pointer error check (IS_ERR())
> >  - change to calloc for easier destroy of bpf_link
> >  - remove perf_event fd list since bpf_link handles fd
> >  - use newer bpf_object__{open/load} API instead of bpf_prog_load
> >  - perf_event for _SC_NPROCESSORS_ONLN instead of _SC_NPROCESSORS_CONF
> >  - find program with name explicitly instead of bpf_program__next
> >  - unconditional bpf_link__destroy() on cleanup
> >
> > Changes in v4:
> >  - bpf_link *, bpf_object * set NULL on init & err for easier destroy
> >  - close bpf object with bpf_object__close()
> >
> > Changes in v5:
> >  - on error, return error code with exit
> >
> >  samples/bpf/Makefile           |   4 +-
> >  samples/bpf/sampleip_user.c    |  98 +++++++++++++++--------
> >  samples/bpf/trace_event_user.c | 139 ++++++++++++++++++++++-----------
> >  3 files changed, 159 insertions(+), 82 deletions(-)
> >
>
> [...]