linux-kernel - Re: [PATCH net-next 14/15 v2] net: Reference bpf_redirect_info via task_struct on PREEMPT

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Message-ID: <20240524135958.I_5-z_K6@linutronix.de>
Date: Fri, 24 May 2024 15:59:58 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Jesper Dangaard Brouer <hawk@...nel.org>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Toke Høiland-Jørgensen <toke@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Boqun Feng <boqun.feng@...il.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Ingo Molnar <mingo@...hat.com>, Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Waiman Long <longman@...hat.com>, Will Deacon <will@...nel.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	Eduard Zingerman <eddyz87@...il.com>, Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>,
	Stanislav Fomichev <sdf@...gle.com>,
	Yonghong Song <yonghong.song@...ux.dev>, bpf <bpf@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH net-next 14/15 v2] net: Reference bpf_redirect_info via
 task_struct on PREEMPT_RT.

On 2024-05-22 09:09:45 [+0200], Jesper Dangaard Brouer wrote:
> For this benchmark, to focus, I would reduce this to:
>   # perf report --sort cpu,symbol --no-children

Keeping the bpf_net_ctx_set()/clear, removing the NULL checks (to align
with Alexei in his last email).
Perf numbers wise, I'm using
	xdp-bench redirect-cpu --cpu 3 --remote-action drop eth1 -e

unpached:

| eth1->?                 9,427,705 rx/s                  0 err,drop/s
|   receive total         9,427,705 pkt/s                 0 drop/s                0 error/s
|     cpu:17              9,427,705 pkt/s                 0 drop/s                0 error/s
|   enqueue to cpu 3      9,427,708 pkt/s                 0 drop/s             8.00 bulk-avg
|     cpu:17->3           9,427,708 pkt/s                 0 drop/s             8.00 bulk-avg
|   kthread total         9,427,710 pkt/s                 0 drop/s          147,276 sched
|     cpu:3               9,427,710 pkt/s                 0 drop/s          147,276 sched
|     xdp_stats                   0 pass/s        9,427,710 drop/s                0 redir/s
|       cpu:3                     0 pass/s        9,427,710 drop/s                0 redir/s
|   redirect_err                  0 error/s
|   xdp_exception                 0 hit/s

Patched:
| eth1->?                 9,557,170 rx/s                  0 err,drop/s
|   receive total         9,557,170 pkt/s                 0 drop/s                0 error/s
|     cpu:9               9,557,170 pkt/s                 0 drop/s                0 error/s
|   enqueue to cpu 3      9,557,170 pkt/s                 0 drop/s             8.00 bulk-avg
|     cpu:9->3            9,557,170 pkt/s                 0 drop/s             8.00 bulk-avg
|   kthread total         9,557,195 pkt/s                 0 drop/s          126,164 sched
|     cpu:3               9,557,195 pkt/s                 0 drop/s          126,164 sched
|     xdp_stats                   0 pass/s        9,557,195 drop/s                0 redir/s
|       cpu:3                     0 pass/s        9,557,195 drop/s                0 redir/s
|   redirect_err                  0 error/s
|   xdp_exception                 0 hit/s

I think this is noise. perf output as suggested (perf report --sort
cpu,symbol --no-children).

unpatched:
|  19.05%  017  [k] bpf_prog_4f0ffbb35139c187_cpumap_l4_hash
|  11.40%  017  [k] ixgbe_poll
|  10.68%  003  [k] cpu_map_kthread_run
|   7.62%  003  [k] intel_idle
|   6.11%  017  [k] xdp_do_redirect
|   6.01%  003  [k] page_frag_free
|   4.72%  017  [k] bq_flush_to_queue
|   3.74%  017  [k] cpu_map_redirect
|   2.35%  003  [k] xdp_return_frame
|   1.55%  003  [k] bpf_prog_57cd311f2e27366b_cpumap_drop
|   1.49%  017  [k] dma_sync_single_for_device
|   1.41%  017  [k] ixgbe_alloc_rx_buffers
|   1.26%  017  [k] cpu_map_enqueue
|   1.24%  017  [k] dma_sync_single_for_cpu
|   1.12%  003  [k] __xdp_return
|   0.83%  017  [k] bpf_trace_run4
|   0.77%  003  [k] __switch_to

patched:
|  18.20%  009  [k] bpf_prog_4f0ffbb35139c187_cpumap_l4_hash
|  11.64%  009  [k] ixgbe_poll
|   7.74%  003  [k] page_frag_free
|   6.69%  003  [k] cpu_map_bpf_prog_run_xdp
|   6.02%  003  [k] intel_idle
|   5.96%  009  [k] xdp_do_redirect
|   4.45%  003  [k] cpu_map_kthread_run
|   3.71%  009  [k] cpu_map_redirect
|   3.23%  009  [k] bq_flush_to_queue
|   2.55%  003  [k] xdp_return_frame
|   1.67%  003  [k] bpf_prog_57cd311f2e27366b_cpumap_drop
|   1.60%  009  [k] _raw_spin_lock
|   1.57%  009  [k] bpf_prog_d7eca17ddc334d36_tp_xdp_cpumap_enqueue
|   1.48%  009  [k] dma_sync_single_for_device
|   1.47%  009  [k] ixgbe_alloc_rx_buffers
|   1.39%  009  [k] dma_sync_single_for_cpu
|   1.33%  009  [k] cpu_map_enqueue
|   1.19%  003  [k] __xdp_return
|   0.66%  003  [k] __switch_to

I'm going to repost the series once the merge window closes unless there
is something you want me to do.

> --Jesper

Sebastian