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Message-ID: <20160406220100.0df04925@redhat.com> Date: Wed, 6 Apr 2016 22:01:00 +0200 From: Jesper Dangaard Brouer <brouer@...hat.com> To: Brenden Blanco <bblanco@...mgrid.com> Cc: davem@...emloft.net, netdev@...r.kernel.org, tom@...bertland.com, alexei.starovoitov@...il.com, Or Gerlitz <ogerlitz@...lanox.com>, daniel@...earbox.net, john.fastabend@...il.com, brouer@...hat.com Subject: Re: [RFC PATCH 5/5] Add sample for adding simple drop program to link On Wed, 6 Apr 2016 21:48:48 +0200 Jesper Dangaard Brouer <brouer@...hat.com> wrote: > I'm testing with this program and these patches, after getting past the > challenge of compiling the samples/bpf files ;-) > > > On Fri, 1 Apr 2016 18:21:58 -0700 Brenden Blanco <bblanco@...mgrid.com> wrote: > > > Add a sample program that only drops packets at the > > BPF_PROG_TYPE_PHYS_DEV hook of a link. With the drop-only program, > > observed single core rate is ~14.6Mpps. > > On my i7-4790K CPU @ 4.00GHz I'm seeing 9.7Mpps (single flow/cpu). > (generator: pktgen_sample03_burst_single_flow.sh) > > # ./netdrvx1 $(</sys/class/net/mlx4p1/ifindex) > sh: /sys/kernel/debug/tracing/kprobe_events: No such file or directory > Success: Loaded file ./netdrvx1_kern.o > proto 17: 9776320 drops/s > > These numbers are quite impressive. Compared to: sending it to local > socket that drop packets 1.7Mpps. Compared to: dropping with iptables > in "raw" table 3.7Mpps. > > If I do multiple flows, via ./pktgen_sample05_flow_per_thread.sh > then I hit this strange 14.5Mpps limit (proto 17: 14505558 drops/s). > And the RX 4x CPUs are starting to NOT use 100% in softirq, they have > some cycles attributed to %idle. (I verified generator is sending at > 24Mpps). > > > > Other tests were run, for instance without the dropcnt increment or > > without reading from the packet header, the packet rate was mostly > > unchanged. > > If I change the program to not touch packet data (don't call > load_byte()) then the performance increase to 14.6Mpps (single > flow/cpu). And the RX CPU is mostly idle... mlx4_en_process_rx_cq() > and page alloc/free functions taking the time. > > > $ perf record -a samples/bpf/netdrvx1 $(</sys/class/net/eth0/ifindex) > > proto 17: 14597724 drops/s > > > > ./pktgen_sample03_burst_single_flow.sh -i $DEV -d $IP -m $MAC -t 4 > > Running... ctrl^C to stop > > Device: eth4@0 > > Result: OK: 6486875(c6485849+d1026) usec, 23689465 (60byte,0frags) > > 3651906pps 1752Mb/sec (1752914880bps) errors: 0 > > Device: eth4@1 > > Result: OK: 6486874(c6485656+d1217) usec, 23689489 (60byte,0frags) > > 3651911pps 1752Mb/sec (1752917280bps) errors: 0 > > Device: eth4@2 > > Result: OK: 6486851(c6485730+d1120) usec, 23687853 (60byte,0frags) > > 3651672pps 1752Mb/sec (1752802560bps) errors: 0 > > Device: eth4@3 > > Result: OK: 6486879(c6485807+d1071) usec, 23688954 (60byte,0frags) > > 3651825pps 1752Mb/sec (1752876000bps) errors: 0 > > > > perf report --no-children: > > 18.36% ksoftirqd/1 [mlx4_en] [k] mlx4_en_process_rx_cq > > 15.98% swapper [kernel.vmlinux] [k] poll_idle > > 12.71% ksoftirqd/1 [mlx4_en] [k] mlx4_en_alloc_frags > > 6.87% ksoftirqd/1 [mlx4_en] [k] mlx4_en_free_frag > > 4.20% ksoftirqd/1 [kernel.vmlinux] [k] get_page_from_freelist > > 4.09% swapper [mlx4_en] [k] mlx4_en_process_rx_cq > > 3.32% ksoftirqd/1 [kernel.vmlinux] [k] sk_load_byte_positive_offset > > 2.39% ksoftirqd/1 [mdio] [k] 0x00000000000074cd > > 2.23% swapper [mlx4_en] [k] mlx4_en_alloc_frags > > 2.20% ksoftirqd/1 [kernel.vmlinux] [k] free_pages_prepare > > 2.08% ksoftirqd/1 [mlx4_en] [k] mlx4_call_bpf > > 1.57% ksoftirqd/1 [kernel.vmlinux] [k] percpu_array_map_lookup_elem > > 1.35% ksoftirqd/1 [mdio] [k] 0x00000000000074fa > > 1.09% ksoftirqd/1 [kernel.vmlinux] [k] free_one_page > > 1.02% ksoftirqd/1 [kernel.vmlinux] [k] bpf_map_lookup_elem > > 0.90% ksoftirqd/1 [kernel.vmlinux] [k] __alloc_pages_nodemask > > 0.88% swapper [kernel.vmlinux] [k] intel_idle > > 0.82% ksoftirqd/1 [mdio] [k] 0x00000000000074be > > 0.80% swapper [mlx4_en] [k] mlx4_en_free_frag > > My picture (single flow/cpu) looks a little bit different: > > + 64.33% ksoftirqd/7 [kernel.vmlinux] [k] __bpf_prog_run > + 9.60% ksoftirqd/7 [mlx4_en] [k] mlx4_en_alloc_frags > + 7.71% ksoftirqd/7 [mlx4_en] [k] mlx4_en_process_rx_cq > + 5.47% ksoftirqd/7 [mlx4_en] [k] mlx4_en_free_frag > + 1.68% ksoftirqd/7 [kernel.vmlinux] [k] get_page_from_freelist > + 1.52% ksoftirqd/7 [mlx4_en] [k] mlx4_call_bpf > + 1.02% ksoftirqd/7 [kernel.vmlinux] [k] free_pages_prepare > + 0.72% ksoftirqd/7 [mlx4_en] [k] mlx4_alloc_pages.isra.20 > + 0.70% ksoftirqd/7 [kernel.vmlinux] [k] __rcu_read_unlock > + 0.65% ksoftirqd/7 [kernel.vmlinux] [k] percpu_array_map_lookup_elem > > On my i7-4790K CPU, I don't have DDIO, thus I assume this high cost in > __bpf_prog_run is due to a cache-miss on the packet data. Before someone else point out the obvious... I forgot to enable JIT. Enable it:: # echo 1 > /proc/sys/net/core/bpf_jit_enable Performance increased to: 10.8Mpps (proto 17: 10819446 drops/s) Samples: 51K of event 'cycles', Event count (approx.): 56775706510 Overhead Command Shared Object Symbol + 55.90% ksoftirqd/7 [kernel.vmlinux] [k] sk_load_byte_positive_offset + 10.71% ksoftirqd/7 [mlx4_en] [k] mlx4_en_alloc_frags + 8.26% ksoftirqd/7 [mlx4_en] [k] mlx4_en_process_rx_cq + 5.94% ksoftirqd/7 [mlx4_en] [k] mlx4_en_free_frag + 2.04% ksoftirqd/7 [kernel.vmlinux] [k] get_page_from_freelist + 2.03% ksoftirqd/7 [kernel.vmlinux] [k] percpu_array_map_lookup_elem + 1.42% ksoftirqd/7 [mlx4_en] [k] mlx4_call_bpf + 1.04% ksoftirqd/7 [kernel.vmlinux] [k] free_pages_prepare + 1.03% ksoftirqd/7 [kernel.vmlinux] [k] __rcu_read_unlock + 0.97% ksoftirqd/7 [mlx4_en] [k] mlx4_alloc_pages.isra.20 + 0.95% ksoftirqd/7 [devlink] [k] 0x0000000000005f87 + 0.58% ksoftirqd/7 [devlink] [k] 0x0000000000005f8f + 0.49% ksoftirqd/7 [kernel.vmlinux] [k] __free_pages_ok + 0.47% ksoftirqd/7 [kernel.vmlinux] [k] __rcu_read_lock + 0.46% ksoftirqd/7 [kernel.vmlinux] [k] free_one_page + 0.38% ksoftirqd/7 [kernel.vmlinux] [k] net_rx_action + 0.36% ksoftirqd/7 [kernel.vmlinux] [k] bpf_map_lookup_elem + 0.36% ksoftirqd/7 [kernel.vmlinux] [k] __mod_zone_page_state + 0.34% ksoftirqd/7 [kernel.vmlinux] [k] __alloc_pages_nodemask + 0.32% ksoftirqd/7 [kernel.vmlinux] [k] _raw_spin_lock + 0.31% ksoftirqd/7 [devlink] [k] 0x0000000000005f0a + 0.29% ksoftirqd/7 [kernel.vmlinux] [k] next_zones_zonelist It is a very likely cache-miss in sk_load_byte_positive_offset(). -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer
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