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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Jesper Dangaard Brouer <jbrouer@redhat.com>
Cc: Stanislav Fomichev <sdf@google.com>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	bpf <bpf@vger.kernel.org>,
	Network Development <netdev@vger.kernel.org>,
	Martin KaFai Lau <martin.lau@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Alexander Lobakin <alexandr.lobakin@intel.com>,
	Larysa Zaremba <larysa.zaremba@intel.com>,
	xdp-hints@xdp-project.net, anthony.l.nguyen@intel.com, "Song,
	Yoong Siang" <yoong.siang.song@intel.com>,
	"Ong, Boon Leong" <boon.leong.ong@intel.com>,
	intel-wired-lan <intel-wired-lan@lists.osuosl.org>,
	Paolo Abeni <pabeni@redhat.com>,
	Jesse Brandeburg <jesse.brandeburg@intel.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Eric Dumazet <edumazet@google.com>,
	John Fastabend <john.fastabend@gmail.com>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	"David S. Miller" <davem@davemloft.net>
Subject: [xdp-hints] Re: [PATCH bpf-next V2 3/6] selftests/bpf: xdp_hw_metadata RX hash return code info
Date: Wed, 22 Mar 2023 09:07:41 -0700	[thread overview]
Message-ID: <CAADnVQKsxzLTZ2XoLbmKKLAeaSyvf3P+w8V143iZ4cEWWTEUfw@mail.gmail.com> (raw)
In-Reply-To: <080640fc-5835-26f1-2b20-ff079bd59182@redhat.com>

On Wed, Mar 22, 2023 at 9:05 AM Jesper Dangaard Brouer
<jbrouer@redhat.com> wrote:
>
>
>
> On 21/03/2023 19.47, Stanislav Fomichev wrote:
> > On Tue, Mar 21, 2023 at 6:47 AM Jesper Dangaard Brouer
> > <brouer@redhat.com> wrote:
> >>
> >> When driver developers add XDP-hints kfuncs for RX hash it is
> >> practical to print the return code in bpf_printk trace pipe log.
> >>
> >> Print hash value as a hex value, both AF_XDP userspace and bpf_prog,
> >> as this makes it easier to spot poor quality hashes.
> >>
> >> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
> >> ---
> >>   .../testing/selftests/bpf/progs/xdp_hw_metadata.c  |    9 ++++++---
> >>   tools/testing/selftests/bpf/xdp_hw_metadata.c      |    5 ++++-
> >>   2 files changed, 10 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c b/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
> >> index 40c17adbf483..ce07010e4d48 100644
> >> --- a/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
> >> +++ b/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
> >> @@ -77,10 +77,13 @@ int rx(struct xdp_md *ctx)
> >>                  meta->rx_timestamp = 0; /* Used by AF_XDP as not avail signal */
> >>          }
> >>
> >> -       if (!bpf_xdp_metadata_rx_hash(ctx, &meta->rx_hash))
> >> -               bpf_printk("populated rx_hash with %u", meta->rx_hash);
> >> -       else
> >> +       ret = bpf_xdp_metadata_rx_hash(ctx, &meta->rx_hash);
> >> +       if (ret >= 0) {
> >> +               bpf_printk("populated rx_hash with 0x%08X", meta->rx_hash);
> >> +       } else {
> >> +               bpf_printk("rx_hash not-avail errno:%d", ret);
> >>                  meta->rx_hash = 0; /* Used by AF_XDP as not avail signal */
> >> +       }
> >>
> >>          return bpf_redirect_map(&xsk, ctx->rx_queue_index, XDP_PASS);
> >>   }
> >> diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c b/tools/testing/selftests/bpf/xdp_hw_metadata.c
> >> index 400bfe19abfe..f3ec07ccdc95 100644
> >> --- a/tools/testing/selftests/bpf/xdp_hw_metadata.c
> >> +++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c
> >> @@ -3,6 +3,9 @@
> >>   /* Reference program for verifying XDP metadata on real HW. Functional test
> >>    * only, doesn't test the performance.
> >>    *
> >> + * BPF-prog bpf_printk info outout can be access via
> >> + * /sys/kernel/debug/tracing/trace_pipe
> >
> > s/outout/output/
> >
>
> Fixed in V3
>
> > But let's maybe drop it? If you want to make it more usable, let's
> > have a separate patch to enable tracing and periodically dump it to
> > the console instead (as previously discussed).
>
> Cat'ing /sys/kernel/debug/tracing/trace_pipe work for me regardless of
> setting in
> /sys/kernel/debug/tracing/events/bpf_trace/bpf_trace_printk/enable
>
> We likely need a followup patch that adds a BPF config switch that can
> disable bpf_printk calls, because this adds overhead and thus affects
> the timestamps.

No. This is by design.
Do not use bpf_printk* in production.

  reply	other threads:[~2023-03-22 16:07 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-21 13:47 [xdp-hints] [PATCH bpf-next V2 0/6] XDP-hints kfuncs for Intel driver igc Jesper Dangaard Brouer
2023-03-21 13:47 ` [xdp-hints] [PATCH bpf-next V2 1/6] igc: enable and fix RX hash usage by netstack Jesper Dangaard Brouer
2023-03-21 13:47 ` [xdp-hints] [PATCH bpf-next V2 2/6] selftests/bpf: xdp_hw_metadata track more timestamps Jesper Dangaard Brouer
2023-03-21 13:47 ` [xdp-hints] [PATCH bpf-next V2 3/6] selftests/bpf: xdp_hw_metadata RX hash return code info Jesper Dangaard Brouer
2023-03-21 18:47   ` [xdp-hints] " Stanislav Fomichev
2023-03-22 16:05     ` Jesper Dangaard Brouer
2023-03-22 16:07       ` Alexei Starovoitov [this message]
2023-03-22 19:00         ` Stanislav Fomichev
2023-03-22 19:17           ` Alexei Starovoitov
2023-03-22 19:22             ` Stanislav Fomichev
2023-03-22 19:30               ` Alexei Starovoitov
2023-03-22 19:33                 ` Stanislav Fomichev
2023-03-23  8:51                   ` Jesper Dangaard Brouer
2023-03-23 17:35                     ` Alexei Starovoitov
2023-03-23 17:47                       ` Stanislav Fomichev
2023-03-24 12:14                         ` Jesper Dangaard Brouer
2023-03-24 19:40                           ` Stanislav Fomichev
2023-03-21 13:47 ` [xdp-hints] [PATCH bpf-next V2 4/6] igc: add igc_xdp_buff wrapper for xdp_buff in driver Jesper Dangaard Brouer
2023-03-21 13:47 ` [xdp-hints] [PATCH bpf-next V2 5/6] igc: add XDP hints kfuncs for RX timestamp Jesper Dangaard Brouer
2023-03-21 13:47 ` [xdp-hints] [PATCH bpf-next V2 6/6] igc: add XDP hints kfuncs for RX hash Jesper Dangaard Brouer

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