From: "Björn Töpel" <bjorn.topel@gmail.com>
To: Jonathan Lemon <jonathan.lemon@gmail.com>
Cc: "Samudrala, Sridhar" <sridhar.samudrala@intel.com>,
"Björn Töpel" <bjorn.topel@intel.com>,
"Karlsson, Magnus" <magnus.karlsson@intel.com>,
Netdev <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
intel-wired-lan <intel-wired-lan@lists.osuosl.org>,
maciej.fijalkowski@intel.com, tom.herbert@intel.com
Subject: Re: [Intel-wired-lan] [PATCH bpf-next 0/5] Add support for SKIP_BPF flag for AF_XDP sockets
Date: Mon, 19 Aug 2019 09:39:28 +0200 [thread overview]
Message-ID: <CAJ+HfNgeSYRuQ8+80zepsAj8f+gdXEqsnbebuvmJggYOBUsj9w@mail.gmail.com> (raw)
In-Reply-To: <331CAEDB-776A-4928-93EF-F45F1339848F@gmail.com>
On Sat, 17 Aug 2019 at 00:08, Jonathan Lemon <jonathan.lemon@gmail.com> wrote:
> On 16 Aug 2019, at 6:32, Björn Töpel wrote:
[...]
> >
> > Today, from a driver perspective, to enable XDP you pass a struct
> > bpf_prog pointer via the ndo_bpf. The program get executed in
> > BPF_PROG_RUN (via bpf_prog_run_xdp) from include/linux/filter.h.
> >
> > I think it's possible to achieve what you're doing w/o *any* driver
> > modification. Pass a special, invalid, pointer to the driver (say
> > (void *)0x1 or smth more elegant), which has a special handling in
> > BPF_RUN_PROG e.g. setting a per-cpu state and return XDP_REDIRECT. The
> > per-cpu state is picked up in xdp_do_redirect and xdp_flush.
> >
> > An approach like this would be general, and apply to all modes
> > automatically.
> >
> > Thoughts?
>
> All the default program does is check that the map entry contains a xsk,
> and call bpf_redirect_map(). So this is pretty much the same as above,
> without any special case handling.
>
> Why would this be so expensive? Is the JIT compilation time being
> counted?
No, not the JIT compilation time, only the fast-path. The gain is from
removing the indirect call (hitting a retpoline) when calling the XDP
program, and reducing code from xdp_do_redirect/xdp_flush.
But, as Jakub pointed out, the XDP batching work by Maciej, might
reduce the retpoline impact quite a bit.
Björn
next prev parent reply other threads:[~2019-08-19 7:39 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-15 3:46 [PATCH bpf-next 0/5] Add support for SKIP_BPF flag for AF_XDP sockets Sridhar Samudrala
2019-08-15 3:46 ` [PATCH bpf-next 1/5] xsk: Convert bool 'zc' field in struct xdp_umem to a u32 bitmap Sridhar Samudrala
2019-08-15 3:46 ` [PATCH bpf-next 2/5] xsk: Introduce XDP_SKIP_BPF bind option Sridhar Samudrala
2019-08-15 3:46 ` [PATCH bpf-next 3/5] i40e: Enable XDP_SKIP_BPF option for AF_XDP sockets Sridhar Samudrala
2019-08-16 9:21 ` kbuild test robot
2019-08-15 3:46 ` [PATCH bpf-next 4/5] ixgbe: " Sridhar Samudrala
2019-08-15 3:46 ` [PATCH bpf-next 5/5] xdpsock_user: Add skip_bpf option Sridhar Samudrala
2019-08-15 11:12 ` [PATCH bpf-next 0/5] Add support for SKIP_BPF flag for AF_XDP sockets Toke Høiland-Jørgensen
2019-08-15 16:25 ` Samudrala, Sridhar
2019-08-15 17:11 ` Toke Høiland-Jørgensen
2019-08-16 6:12 ` Samudrala, Sridhar
2019-08-15 12:51 ` Björn Töpel
2019-08-15 16:46 ` Samudrala, Sridhar
2019-08-16 13:32 ` [Intel-wired-lan] " Björn Töpel
2019-08-16 22:08 ` Jonathan Lemon
2019-08-19 7:39 ` Björn Töpel [this message]
2019-08-15 19:28 ` Jakub Kicinski
2019-08-16 6:25 ` Samudrala, Sridhar
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