From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: "Samudrala, Sridhar" <sridhar.samudrala@intel.com>
Cc: "Toke Høiland-Jørgensen" <toke@redhat.com>,
"Jakub Kicinski" <jakub.kicinski@netronome.com>,
"Karlsson, Magnus" <magnus.karlsson@intel.com>,
"Björn Töpel" <bjorn.topel@intel.com>,
Netdev <netdev@vger.kernel.org>,
"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
intel-wired-lan <intel-wired-lan@lists.osuosl.org>,
"Fijalkowski, Maciej" <maciej.fijalkowski@intel.com>,
"Herbert, Tom" <tom.herbert@intel.com>
Subject: Re: FW: [PATCH bpf-next 2/4] xsk: allow AF_XDP sockets to receive packets directly from a queue
Date: Fri, 18 Oct 2019 19:25:27 -0700 [thread overview]
Message-ID: <20191019022525.w5xbwkav2cpqkfwi@ast-mbp> (raw)
In-Reply-To: <6f281517-3785-ce46-65de-e2f78576783b@intel.com>
On Fri, Oct 18, 2019 at 05:45:26PM -0700, Samudrala, Sridhar wrote:
> On 10/18/2019 5:14 PM, Alexei Starovoitov wrote:
> > On Fri, Oct 18, 2019 at 11:40:07AM -0700, Samudrala, Sridhar wrote:
> > >
> > > Perf report for "AF_XDP default rxdrop" with patched kernel - mitigations ON
> > > ==========================================================================
> > > Samples: 44K of event 'cycles', Event count (approx.): 38532389541
> > > Overhead Command Shared Object Symbol
> > > 15.31% ksoftirqd/28 [i40e] [k] i40e_clean_rx_irq_zc
> > > 10.50% ksoftirqd/28 bpf_prog_80b55d8a76303785 [k] bpf_prog_80b55d8a76303785
> > > 9.48% xdpsock [i40e] [k] i40e_clean_rx_irq_zc
> > > 8.62% xdpsock xdpsock [.] main
> > > 7.11% ksoftirqd/28 [kernel.vmlinux] [k] xsk_rcv
> > > 5.81% ksoftirqd/28 [kernel.vmlinux] [k] xdp_do_redirect
> > > 4.46% xdpsock bpf_prog_80b55d8a76303785 [k] bpf_prog_80b55d8a76303785
> > > 3.83% xdpsock [kernel.vmlinux] [k] xsk_rcv
> >
> > why everything is duplicated?
> > Same code runs in different tasks ?
>
> Yes. looks like these functions run from both the app(xdpsock) context and ksoftirqd context.
>
> >
> > > 2.81% ksoftirqd/28 [kernel.vmlinux] [k] bpf_xdp_redirect_map
> > > 2.78% ksoftirqd/28 [kernel.vmlinux] [k] xsk_map_lookup_elem
> > > 2.44% xdpsock [kernel.vmlinux] [k] xdp_do_redirect
> > > 2.19% ksoftirqd/28 [kernel.vmlinux] [k] __xsk_map_redirect
> > > 1.62% ksoftirqd/28 [kernel.vmlinux] [k] xsk_umem_peek_addr
> > > 1.57% xdpsock [kernel.vmlinux] [k] xsk_umem_peek_addr
> > > 1.32% ksoftirqd/28 [kernel.vmlinux] [k] dma_direct_sync_single_for_cpu
> > > 1.28% xdpsock [kernel.vmlinux] [k] bpf_xdp_redirect_map
> > > 1.15% xdpsock [kernel.vmlinux] [k] dma_direct_sync_single_for_device
> > > 1.12% xdpsock [kernel.vmlinux] [k] xsk_map_lookup_elem
> > > 1.06% xdpsock [kernel.vmlinux] [k] __xsk_map_redirect
> > > 0.94% ksoftirqd/28 [kernel.vmlinux] [k] dma_direct_sync_single_for_device
> > > 0.75% ksoftirqd/28 [kernel.vmlinux] [k] __x86_indirect_thunk_rax
> > > 0.66% ksoftirqd/28 [i40e] [k] i40e_clean_programming_status
> > > 0.64% ksoftirqd/28 [kernel.vmlinux] [k] net_rx_action
> > > 0.64% swapper [kernel.vmlinux] [k] intel_idle
> > > 0.62% ksoftirqd/28 [i40e] [k] i40e_napi_poll
> > > 0.57% xdpsock [kernel.vmlinux] [k] dma_direct_sync_single_for_cpu
> > >
> > > Perf report for "AF_XDP direct rxdrop" with patched kernel - mitigations ON
> > > ==========================================================================
> > > Samples: 46K of event 'cycles', Event count (approx.): 38387018585
> > > Overhead Command Shared Object Symbol
> > > 21.94% ksoftirqd/28 [i40e] [k] i40e_clean_rx_irq_zc
> > > 14.36% xdpsock xdpsock [.] main
> > > 11.53% ksoftirqd/28 [kernel.vmlinux] [k] xsk_rcv
> > > 11.32% xdpsock [i40e] [k] i40e_clean_rx_irq_zc
> > > 4.02% xdpsock [kernel.vmlinux] [k] xsk_rcv
> > > 2.91% ksoftirqd/28 [kernel.vmlinux] [k] xdp_do_redirect
> > > 2.45% ksoftirqd/28 [kernel.vmlinux] [k] xsk_umem_peek_addr
> > > 2.19% xdpsock [kernel.vmlinux] [k] xsk_umem_peek_addr
> > > 2.08% ksoftirqd/28 [kernel.vmlinux] [k] bpf_direct_xsk
> > > 2.07% ksoftirqd/28 [kernel.vmlinux] [k] dma_direct_sync_single_for_cpu
> > > 1.53% ksoftirqd/28 [kernel.vmlinux] [k] dma_direct_sync_single_for_device
> > > 1.39% xdpsock [kernel.vmlinux] [k] dma_direct_sync_single_for_device
> > > 1.22% ksoftirqd/28 [kernel.vmlinux] [k] xdp_get_xsk_from_qid
> > > 1.12% ksoftirqd/28 [i40e] [k] i40e_clean_programming_status
> > > 0.96% ksoftirqd/28 [i40e] [k] i40e_napi_poll
> > > 0.95% ksoftirqd/28 [kernel.vmlinux] [k] net_rx_action
> > > 0.89% xdpsock [kernel.vmlinux] [k] xdp_do_redirect
> > > 0.83% swapper [i40e] [k] i40e_clean_rx_irq_zc
> > > 0.70% swapper [kernel.vmlinux] [k] intel_idle
> > > 0.66% xdpsock [kernel.vmlinux] [k] dma_direct_sync_single_for_cpu
> > > 0.60% xdpsock [kernel.vmlinux] [k] bpf_direct_xsk
> > > 0.50% ksoftirqd/28 [kernel.vmlinux] [k] xsk_umem_discard_addr
> > >
> > > Based on the perf reports comparing AF_XDP default and direct rxdrop, we can say that
> > > AF_XDP direct rxdrop codepath is avoiding the overhead of going through these functions
> > > bpf_prog_xxx
> > > bpf_xdp_redirect_map
> > > xsk_map_lookup_elem
> > > __xsk_map_redirect
> > > With AF_XDP direct, xsk_rcv() is directly called via bpf_direct_xsk() in xdp_do_redirect()
> >
> > I don't think you're identifying the overhead correctly.
> > xsk_map_lookup_elem is 1%
> > but bpf_xdp_redirect_map() suppose to call __xsk_map_lookup_elem()
> > which is a different function:
> > ffffffff81493fe0 T __xsk_map_lookup_elem
> > ffffffff81492e80 t xsk_map_lookup_elem
> >
> > 10% for bpf_prog_80b55d8a76303785 is huge.
> > It's the actual code of the program _without_ any helpers.
> > How does the program actually look?
>
> It is the xdp program that is loaded via xsk_load_xdp_prog() in tools/lib/bpf/xsk.c
> https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/tools/lib/bpf/xsk.c#n268
I see. Looks like map_gen_lookup was never implemented for xskmap.
How about adding it first the way array_map_gen_lookup() is implemented?
This will easily give 2x perf gain.
next prev parent reply other threads:[~2019-10-19 2:25 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-08 6:16 [PATCH bpf-next 0/4] Enable direct receive on AF_XDP sockets Sridhar Samudrala
2019-10-08 6:16 ` [PATCH bpf-next 1/4] bpf: introduce bpf_get_prog_id and bpf_set_prog_id helper functions Sridhar Samudrala
2019-10-08 6:16 ` [PATCH bpf-next 2/4] xsk: allow AF_XDP sockets to receive packets directly from a queue Sridhar Samudrala
2019-10-08 6:58 ` Toke Høiland-Jørgensen
2019-10-08 8:47 ` Björn Töpel
2019-10-08 8:48 ` Björn Töpel
2019-10-08 9:04 ` Toke Høiland-Jørgensen
2019-10-08 8:05 ` Björn Töpel
2019-10-09 16:32 ` Samudrala, Sridhar
2019-10-09 1:20 ` Alexei Starovoitov
[not found] ` <3ED8E928C4210A4289A677D2FEB48235140134CE@fmsmsx111.amr.corp.intel.com>
2019-10-09 16:53 ` FW: " Samudrala, Sridhar
2019-10-09 17:17 ` Alexei Starovoitov
2019-10-09 19:12 ` Samudrala, Sridhar
2019-10-10 1:06 ` Alexei Starovoitov
2019-10-18 18:40 ` Samudrala, Sridhar
2019-10-18 19:22 ` Toke Høiland-Jørgensen
2019-10-19 0:14 ` Alexei Starovoitov
2019-10-19 0:45 ` Samudrala, Sridhar
2019-10-19 2:25 ` Alexei Starovoitov [this message]
2019-10-20 10:14 ` Toke Høiland-Jørgensen
2019-10-20 17:12 ` [Intel-wired-lan] " Björn Töpel
2019-10-21 20:10 ` Samudrala, Sridhar
2019-10-21 22:34 ` Alexei Starovoitov
2019-10-22 19:06 ` Samudrala, Sridhar
2019-10-23 17:42 ` Alexei Starovoitov
2019-10-24 18:12 ` Samudrala, Sridhar
2019-10-25 7:42 ` Björn Töpel
2019-10-31 22:38 ` Samudrala, Sridhar
2019-10-31 23:15 ` Alexei Starovoitov
2019-11-01 0:21 ` Jakub Kicinski
2019-11-01 18:31 ` Samudrala, Sridhar
2019-11-04 2:08 ` dan
2019-10-25 9:07 ` Björn Töpel
2019-10-08 6:16 ` [PATCH bpf-next 3/4] libbpf: handle AF_XDP sockets created with XDP_DIRECT bind flag Sridhar Samudrala
2019-10-08 8:05 ` Björn Töpel
2019-10-08 6:16 ` [PATCH bpf-next 4/4] xdpsock: add an option to create AF_XDP sockets in XDP_DIRECT mode Sridhar Samudrala
2019-10-08 8:05 ` Björn Töpel
2019-10-08 8:05 ` [PATCH bpf-next 0/4] Enable direct receive on AF_XDP sockets Björn Töpel
2019-10-09 16:19 ` Samudrala, Sridhar
2019-10-09 0:49 ` Jakub Kicinski
2019-10-09 6:29 ` Samudrala, Sridhar
2019-10-09 16:53 ` Jakub Kicinski
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