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From: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
To: Larysa Zaremba <larysa.zaremba@intel.com>
Cc: Magnus Karlsson <magnus.karlsson@gmail.com>,
	bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net,
	andrii@kernel.org, martin.lau@linux.dev, song@kernel.org,
	yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org,
	sdf@google.com, haoluo@google.com, jolsa@kernel.org,
	David Ahern <dsahern@gmail.com>, Jakub Kicinski <kuba@kernel.org>,
	Willem de Bruijn <willemb@google.com>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	Anatoly Burakov <anatoly.burakov@intel.com>,
	Alexander Lobakin <alexandr.lobakin@intel.com>,
	Maryam Tahhan <mtahhan@redhat.com>,
	xdp-hints@xdp-project.net, netdev@vger.kernel.org,
	Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Simon Horman <simon.horman@corigine.com>,
	Tariq Toukan <tariqt@mellanox.com>,
	Saeed Mahameed <saeedm@mellanox.com>,
	magnus.karlsson@intel.com
Subject: [xdp-hints] Re: [PATCH bpf-next v6 07/18] ice: Support XDP hints in AF_XDP ZC mode
Date: Wed, 18 Oct 2023 12:43:06 +0200	[thread overview]
Message-ID: <ZS+2urlM5zqcJ6S5@boxer> (raw)
In-Reply-To: <ZS6+fcfjQgIdD+6G@lzaremba-mobl.ger.corp.intel.com>

On Tue, Oct 17, 2023 at 07:03:57PM +0200, Larysa Zaremba wrote:
> On Tue, Oct 17, 2023 at 06:45:02PM +0200, Maciej Fijalkowski wrote:
> > On Tue, Oct 17, 2023 at 06:37:07PM +0200, Magnus Karlsson wrote:
> > > On Tue, 17 Oct 2023 at 18:13, Maciej Fijalkowski
> > > <maciej.fijalkowski@intel.com> wrote:
> > > >
> > > > On Thu, Oct 12, 2023 at 07:05:13PM +0200, Larysa Zaremba wrote:
> > > > > In AF_XDP ZC, xdp_buff is not stored on ring,
> > > > > instead it is provided by xsk_buff_pool.
> > > > > Space for metadata sources right after such buffers was already reserved
> > > > > in commit 94ecc5ca4dbf ("xsk: Add cb area to struct xdp_buff_xsk").
> > > > > This makes the implementation rather straightforward.
> > > > >
> > > > > Update AF_XDP ZC packet processing to support XDP hints.
> > > > >
> > > > > Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
> > > > > ---
> > > > >  drivers/net/ethernet/intel/ice/ice_xsk.c | 34 ++++++++++++++++++++++--
> > > > >  1 file changed, 32 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
> > > > > index ef778b8e6d1b..6ca620b2fbdd 100644
> > > > > --- a/drivers/net/ethernet/intel/ice/ice_xsk.c
> > > > > +++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
> > > > > @@ -752,22 +752,51 @@ static int ice_xmit_xdp_tx_zc(struct xdp_buff *xdp,
> > > > >       return ICE_XDP_CONSUMED;
> > > > >  }
> > > > >
> > > > > +/**
> > > > > + * ice_prepare_pkt_ctx_zc - Prepare packet context for XDP hints
> > > > > + * @xdp: xdp_buff used as input to the XDP program
> > > > > + * @eop_desc: End of packet descriptor
> > > > > + * @rx_ring: Rx ring with packet context
> > > > > + *
> > > > > + * In regular XDP, xdp_buff is placed inside the ring structure,
> > > > > + * just before the packet context, so the latter can be accessed
> > > > > + * with xdp_buff address only at all times, but in ZC mode,
> > > > > + * xdp_buffs come from the pool, so we need to reinitialize
> > > > > + * context for every packet.
> > > > > + *
> > > > > + * We can safely convert xdp_buff_xsk to ice_xdp_buff,
> > > > > + * because there are XSK_PRIV_MAX bytes reserved in xdp_buff_xsk
> > > > > + * right after xdp_buff, for our private use.
> > > > > + * XSK_CHECK_PRIV_TYPE() ensures we do not go above the limit.
> > > > > + */
> > > > > +static void ice_prepare_pkt_ctx_zc(struct xdp_buff *xdp,
> > > > > +                                union ice_32b_rx_flex_desc *eop_desc,
> > > > > +                                struct ice_rx_ring *rx_ring)
> > > > > +{
> > > > > +     XSK_CHECK_PRIV_TYPE(struct ice_xdp_buff);
> > > > > +     ((struct ice_xdp_buff *)xdp)->pkt_ctx = rx_ring->pkt_ctx;
> > > >
> > > > I will be loud thinking over here, but this could be set in
> > > > ice_fill_rx_descs(), while grabbing xdp_buffs from xsk_pool, should
> > > > minimize the performance overhead.
> 
> I am not sure about that. Packet context consists of:
> * VLAN protocol
> * cached time
> 
> Both of those can be updated without stopping traffic, so we cannot set this 
> at setup time.

I was referring to setting the pointer to pkt_ctx. Similarly mlx5 sets
setting pointer to rq during alloc but cqe ptr is set per packet.

Regardless, let us proceed with what you have and later on maybe address
what I was bringing up here.

> 
> > > >
> > > > But then again you address that with static branch in later patch.
> > > >
> > > > OTOH, I was thinking that we could come with xsk_buff_pool API that would
> > > > let drivers assign this at setup time. Similar what is being done with dma
> > > > mappings.
> > > >
> > > > Magnus, do you think it is worth the hassle? Thoughts?
> > > 
> > > I would measure the overhead of the current assignment and if it is
> > > significant (incurs a cache miss for example), then why not try out
> > > your idea. Usually good not to have to touch things when not needed.
> > 
> > Larysa measured that because I asked for that previously and impact was
> > around 6%. Then look at patch 11/18 how this was addressed.
> > 
> > Other ZC drivers didn't report the impact but i am rather sure they were also
> > affected. So i was thinking whether we should have some generic solution
> > within pool or every ZC driver handles that on its own.
> > 
> > > 
> > > > Or should we advise any other driver that support hints to mimic static
> > > > branch solution?
> > > >
> > > > > +     ice_xdp_meta_set_desc(xdp, eop_desc);
> > > > > +}
> > > > > +
> > > > >  /**
> > > > >   * ice_run_xdp_zc - Executes an XDP program in zero-copy path
> > > > >   * @rx_ring: Rx ring
> > > > >   * @xdp: xdp_buff used as input to the XDP program
> > > > >   * @xdp_prog: XDP program to run
> > > > >   * @xdp_ring: ring to be used for XDP_TX action
> > > > > + * @rx_desc: packet descriptor
> > > > >   *
> > > > >   * Returns any of ICE_XDP_{PASS, CONSUMED, TX, REDIR}
> > > > >   */
> > > > >  static int
> > > > >  ice_run_xdp_zc(struct ice_rx_ring *rx_ring, struct xdp_buff *xdp,
> > > > > -            struct bpf_prog *xdp_prog, struct ice_tx_ring *xdp_ring)
> > > > > +            struct bpf_prog *xdp_prog, struct ice_tx_ring *xdp_ring,
> > > > > +            union ice_32b_rx_flex_desc *rx_desc)
> > > > >  {
> > > > >       int err, result = ICE_XDP_PASS;
> > > > >       u32 act;
> > > > >
> > > > > +     ice_prepare_pkt_ctx_zc(xdp, rx_desc, rx_ring);
> > > > >       act = bpf_prog_run_xdp(xdp_prog, xdp);
> > > > >
> > > > >       if (likely(act == XDP_REDIRECT)) {
> > > > > @@ -907,7 +936,8 @@ int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget)
> > > > >               if (ice_is_non_eop(rx_ring, rx_desc))
> > > > >                       continue;
> > > > >
> > > > > -             xdp_res = ice_run_xdp_zc(rx_ring, first, xdp_prog, xdp_ring);
> > > > > +             xdp_res = ice_run_xdp_zc(rx_ring, first, xdp_prog, xdp_ring,
> > > > > +                                      rx_desc);
> > > > >               if (likely(xdp_res & (ICE_XDP_TX | ICE_XDP_REDIR))) {
> > > > >                       xdp_xmit |= xdp_res;
> > > > >               } else if (xdp_res == ICE_XDP_EXIT) {
> > > > > --
> > > > > 2.41.0
> > > > >

  reply	other threads:[~2023-10-18 10:43 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-12 17:05 [xdp-hints] [PATCH bpf-next v6 00/18] XDP metadata via kfuncs for ice + VLAN hint Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 01/18] ice: make RX hash reading code more reusable Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 02/18] ice: make RX HW timestamp " Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 03/18] ice: Make ptype internal to descriptor info processing Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 04/18] ice: Introduce ice_xdp_buff Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 05/18] ice: Support HW timestamp hint Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 06/18] ice: Support RX hash XDP hint Larysa Zaremba
2023-10-20 15:27   ` [xdp-hints] " Maciej Fijalkowski
2023-10-23 10:04     ` Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 07/18] ice: Support XDP hints in AF_XDP ZC mode Larysa Zaremba
2023-10-17 16:13   ` [xdp-hints] " Maciej Fijalkowski
2023-10-17 16:37     ` Magnus Karlsson
2023-10-17 16:45       ` Maciej Fijalkowski
2023-10-17 17:03         ` Larysa Zaremba
2023-10-18 10:43           ` Maciej Fijalkowski [this message]
2023-10-20 15:29   ` Maciej Fijalkowski
2023-10-23  9:37     ` Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 08/18] xdp: Add VLAN tag hint Larysa Zaremba
2023-10-18 23:59   ` [xdp-hints] " Jakub Kicinski
2023-10-19  8:05     ` Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 09/18] ice: Implement " Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 10/18] ice: use VLAN proto from ring packet context in skb path Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 11/18] ice: put XDP meta sources assignment under a static key condition Larysa Zaremba
2023-10-20 16:32   ` [xdp-hints] " Maciej Fijalkowski
2023-10-23  9:35     ` Larysa Zaremba
2023-10-28 19:55       ` Maciej Fijalkowski
2023-10-31 14:22         ` Larysa Zaremba
2023-11-02 13:23           ` Maciej Fijalkowski
2023-11-02 13:48             ` Larysa Zaremba
2023-10-31 17:32         ` Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 12/18] veth: Implement VLAN tag XDP hint Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 13/18] net: make vlan_get_tag() return -ENODATA instead of -EINVAL Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 14/18] mlx5: implement VLAN tag XDP hint Larysa Zaremba
2023-10-17 12:40   ` [xdp-hints] " Tariq Toukan
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 15/18] selftests/bpf: Allow VLAN packets in xdp_hw_metadata Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 16/18] selftests/bpf: Add flags and VLAN hint to xdp_hw_metadata Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 17/18] selftests/bpf: Use AF_INET for TX in xdp_metadata Larysa Zaremba
2023-10-12 17:05 ` [xdp-hints] [PATCH bpf-next v6 18/18] selftests/bpf: Check VLAN tag and proto " Larysa Zaremba

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