bpf.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: "Björn Töpel" <bjorn.topel@gmail.com>,
	netdev@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net
Cc: "Björn Töpel" <bjorn.topel@intel.com>,
	bpf@vger.kernel.org, magnus.karlsson@gmail.com,
	magnus.karlsson@intel.com, sridhar.samudrala@intel.com
Subject: Re: [PATCH bpf-next v2] libbpf: use implicit XSKMAP lookup from AF_XDP XDP program
Date: Mon, 21 Oct 2019 13:50:25 +0200	[thread overview]
Message-ID: <87h842qpvi.fsf@toke.dk> (raw)
In-Reply-To: <20191021105938.11820-1-bjorn.topel@gmail.com>

Björn Töpel <bjorn.topel@gmail.com> writes:

> From: Björn Töpel <bjorn.topel@intel.com>
>
> In commit 43e74c0267a3 ("bpf_xdp_redirect_map: Perform map lookup in
> eBPF helper") the bpf_redirect_map() helper learned to do map lookup,
> which means that the explicit lookup in the XDP program for AF_XDP is
> not needed for post-5.3 kernels.
>
> This commit adds the implicit map lookup with default action, which
> improves the performance for the "rx_drop" [1] scenario with ~4%.
>
> For pre-5.3 kernels, the bpf_redirect_map() returns XDP_ABORTED, and a
> fallback path for backward compatibility is entered, where explicit
> lookup is still performed. This means a slight regression for older
> kernels (an additional bpf_redirect_map() call), but I consider that a
> fair punishment for users not upgrading their kernels. ;-)
>
> v1->v2: Backward compatibility (Toke) [2]
>
> [1] # xdpsock -i eth0 -z -r
> [2] https://lore.kernel.org/bpf/87pnirb3dc.fsf@toke.dk/
>
> Suggested-by: Toke Høiland-Jørgensen <toke@redhat.com>
> Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
> ---
>  tools/lib/bpf/xsk.c | 45 +++++++++++++++++++++++++++++++++++----------
>  1 file changed, 35 insertions(+), 10 deletions(-)
>
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index b0f532544c91..391a126b3fd8 100644
> --- a/tools/lib/bpf/xsk.c
> +++ b/tools/lib/bpf/xsk.c
> @@ -274,33 +274,58 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
>  	/* This is the C-program:
>  	 * SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx)
>  	 * {
> -	 *     int index = ctx->rx_queue_index;
> +	 *     int ret, index = ctx->rx_queue_index;
>  	 *
>  	 *     // A set entry here means that the correspnding queue_id
>  	 *     // has an active AF_XDP socket bound to it.
> +	 *     ret = bpf_redirect_map(&xsks_map, index, XDP_PASS);
> +	 *     ret &= XDP_PASS | XDP_REDIRECT;

Why the masking? Looks a bit weird (XDP return codes are not defined as
bitmask values), and it's not really needed, is it?

-Toke


  reply	other threads:[~2019-10-21 11:50 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-21 10:59 Björn Töpel
2019-10-21 11:50 ` Toke Høiland-Jørgensen [this message]
2019-10-21 12:02   ` Björn Töpel
2019-10-21 12:19     ` Toke Høiland-Jørgensen
2019-10-21 13:37       ` Björn Töpel
2019-10-21 14:35         ` Björn Töpel
2019-10-21 15:43           ` Toke Høiland-Jørgensen
2019-10-22  7:16             ` Björn Töpel

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=87h842qpvi.fsf@toke.dk \
    --to=toke@redhat.com \
    --cc=ast@kernel.org \
    --cc=bjorn.topel@gmail.com \
    --cc=bjorn.topel@intel.com \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=magnus.karlsson@gmail.com \
    --cc=magnus.karlsson@intel.com \
    --cc=netdev@vger.kernel.org \
    --cc=sridhar.samudrala@intel.com \
    --subject='Re: [PATCH bpf-next v2] libbpf: use implicit XSKMAP lookup from AF_XDP XDP program' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).