linux_dsm_epyc7002/net/ipv4
Eric Dumazet 218af599fa tcp: internal implementation for pacing
BBR congestion control depends on pacing, and pacing is
currently handled by sch_fq packet scheduler for performance reasons,
and also because implemening pacing with FQ was convenient to truly
avoid bursts.

However there are many cases where this packet scheduler constraint
is not practical.
- Many linux hosts are not focusing on handling thousands of TCP
  flows in the most efficient way.
- Some routers use fq_codel or other AQM, but still would like
  to use BBR for the few TCP flows they initiate/terminate.

This patch implements an automatic fallback to internal pacing.

Pacing is requested either by BBR or use of SO_MAX_PACING_RATE option.

If sch_fq happens to be in the egress path, pacing is delegated to
the qdisc, otherwise pacing is done by TCP itself.

One advantage of pacing from TCP stack is to get more precise rtt
estimations, and less work done from TX completion, since TCP Small
queue limits are not generally hit. Setups with single TX queue but
many cpus might even benefit from this.

Note that unlike sch_fq, we do not take into account header sizes.
Taking care of these headers would add additional complexity for
no practical differences in behavior.

Some performance numbers using 800 TCP_STREAM flows rate limited to
~48 Mbit per second on 40Gbit NIC.

If MQ+pfifo_fast is used on the NIC :

$ sar -n DEV 1 5 | grep eth
14:48:44         eth0 725743.00 2932134.00  46776.76 4335184.68      0.00      0.00      1.00
14:48:45         eth0 725349.00 2932112.00  46751.86 4335158.90      0.00      0.00      0.00
14:48:46         eth0 725101.00 2931153.00  46735.07 4333748.63      0.00      0.00      0.00
14:48:47         eth0 725099.00 2931161.00  46735.11 4333760.44      0.00      0.00      1.00
14:48:48         eth0 725160.00 2931731.00  46738.88 4334606.07      0.00      0.00      0.00
Average:         eth0 725290.40 2931658.20  46747.54 4334491.74      0.00      0.00      0.40
$ vmstat 1 5
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 4  0      0 259825920  45644 2708324    0    0    21     2  247   98  0  0 100  0  0
 4  0      0 259823744  45644 2708356    0    0     0     0 2400825 159843  0 19 81  0  0
 0  0      0 259824208  45644 2708072    0    0     0     0 2407351 159929  0 19 81  0  0
 1  0      0 259824592  45644 2708128    0    0     0     0 2405183 160386  0 19 80  0  0
 1  0      0 259824272  45644 2707868    0    0     0    32 2396361 158037  0 19 81  0  0

Now use MQ+FQ :

lpaa23:~# echo fq >/proc/sys/net/core/default_qdisc
lpaa23:~# tc qdisc replace dev eth0 root mq

$ sar -n DEV 1 5 | grep eth
14:49:57         eth0 678614.00 2727930.00  43739.13 4033279.14      0.00      0.00      0.00
14:49:58         eth0 677620.00 2723971.00  43674.69 4027429.62      0.00      0.00      1.00
14:49:59         eth0 676396.00 2719050.00  43596.83 4020125.02      0.00      0.00      0.00
14:50:00         eth0 675197.00 2714173.00  43518.62 4012938.90      0.00      0.00      1.00
14:50:01         eth0 676388.00 2719063.00  43595.47 4020171.64      0.00      0.00      0.00
Average:         eth0 676843.00 2720837.40  43624.95 4022788.86      0.00      0.00      0.40
$ vmstat 1 5
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 2  0      0 259832240  46008 2710912    0    0    21     2  223  192  0  1 99  0  0
 1  0      0 259832896  46008 2710744    0    0     0     0 1702206 198078  0 17 82  0  0
 0  0      0 259830272  46008 2710596    0    0     0     0 1696340 197756  1 17 83  0  0
 4  0      0 259829168  46024 2710584    0    0    16     0 1688472 197158  1 17 82  0  0
 3  0      0 259830224  46024 2710408    0    0     0     0 1692450 197212  0 18 82  0  0

As expected, number of interrupts per second is very different.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Van Jacobson <vanj@google.com>
Cc: Jerry Chu <hkchu@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-05-16 15:43:31 -04:00
..
netfilter Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf-next 2017-05-01 10:47:53 -04:00
af_inet.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2017-05-02 16:40:27 -07:00
ah4.c
arp.c neighbour: fix nlmsg_pid in notifications 2017-03-22 10:48:49 -07:00
cipso_ipv4.c netlabel: out of bound access in cipso_v4_validate() 2017-02-04 19:44:22 -05:00
datagram.c
devinet.c net: rtnetlink: plumb extended ack to doit function 2017-04-17 15:35:38 -04:00
esp4_offload.c esp4/6: Fix GSO path for non-GSO SW-crypto packets 2017-04-19 07:48:57 +02:00
esp4.c net/esp4: Fix invalid esph pointer crash 2017-05-01 14:58:50 -04:00
fib_frontend.c net: fib: Decrease one unnecessary rt cache flush in fib_disable_ip 2017-04-27 16:33:30 -04:00
fib_lookup.h
fib_notifier.c ipv4: fib: Remove redundant argument 2017-03-10 09:45:09 -08:00
fib_rules.c ipv4: fib_rules: Dump FIB rules when registering FIB notifier 2017-03-16 10:18:34 -07:00
fib_semantics.c net: ipv4: add support for ECMP hash policy choice 2017-03-21 15:27:19 -07:00
fib_trie.c ipv4: fib: Remove redundant argument 2017-03-10 09:45:09 -08:00
fou.c
gre_demux.c
gre_offload.c
icmp.c net: ipv4: add support for ECMP hash policy choice 2017-03-21 15:27:19 -07:00
igmp.c igmp, mld: Fix memory leak in igmpv3/mld_del_delrec() 2017-02-09 16:43:45 -05:00
inet_connection_sock.c dccp/tcp: do not inherit mc_list from parent 2017-05-09 15:17:49 -04:00
inet_diag.c
inet_fragment.c
inet_hashtables.c treewide: use kv[mz]alloc* rather than opencoded variants 2017-05-08 17:15:13 -07:00
inet_timewait_sock.c
inetpeer.c
ip_forward.c
ip_fragment.c inet: frag: release spinlock before calling icmp_send() 2017-03-22 15:40:45 -07:00
ip_gre.c ip_tunnel: Allow policy-based routing through tunnels 2017-04-21 13:21:31 -04:00
ip_input.c net: Add sysctl to toggle early demux for tcp and udp 2017-03-24 13:17:07 -07:00
ip_options.c
ip_output.c udp: avoid ufo handling on IP payload compression packets 2017-03-09 18:28:42 -08:00
ip_sockglue.c ipv4: get rid of ip_ra_lock 2017-04-30 22:44:04 -04:00
ip_tunnel_core.c netlink: pass extended ACK struct to parsing functions 2017-04-13 13:58:22 -04:00
ip_tunnel.c ip_tunnel: Allow policy-based routing through tunnels 2017-04-21 13:21:31 -04:00
ip_vti.c vti: check nla_put_* return value 2017-05-08 15:10:31 -04:00
ipcomp.c
ipconfig.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-04-06 08:24:51 -07:00
ipip.c ip_tunnel: Allow policy-based routing through tunnels 2017-04-21 13:21:31 -04:00
ipmr.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-04-20 10:35:33 -04:00
Kconfig Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec-next 2017-02-16 21:25:49 -05:00
Makefile ipv4: fib: Move FIB notification code to a separate file 2017-03-10 09:45:09 -08:00
netfilter.c netfilter: use skb_to_full_sk in ip_route_me_harder 2017-02-28 12:49:36 +01:00
ping.c ping: implement proper locking 2017-03-24 20:50:28 -07:00
proc.c net/tcp_fastopen: Add snmp counter for blackhole detection 2017-04-24 14:27:17 -04:00
protocol.c net: Add sysctl to toggle early demux for tcp and udp 2017-03-24 13:17:07 -07:00
raw_diag.c
raw.c ipv4, ipv6: ensure raw socket message is big enough to hold an IP header 2017-05-04 11:02:46 -04:00
route.c Revert "ipv4: restore rt->fi for reference counting" 2017-05-08 22:35:32 -04:00
syncookies.c tcp: randomize timestamps on syncookies 2017-05-05 12:00:11 -04:00
sysctl_net_ipv4.c net/tcp_fastopen: Disable active side TFO in certain scenarios 2017-04-24 14:27:17 -04:00
tcp_bbr.c tcp: internal implementation for pacing 2017-05-16 15:43:31 -04:00
tcp_bic.c
tcp_cdg.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/clock.h> 2017-03-02 08:42:27 +01:00
tcp_cong.c tcp: memset ca_priv data to 0 properly 2017-04-26 14:58:32 -04:00
tcp_cubic.c tcp_cubic: fix typo in module param description 2017-04-20 16:16:44 -04:00
tcp_dctcp.c
tcp_diag.c
tcp_fastopen.c net/tcp_fastopen: Add snmp counter for blackhole detection 2017-04-24 14:27:17 -04:00
tcp_highspeed.c
tcp_htcp.c
tcp_hybla.c
tcp_illinois.c
tcp_input.c tcp: avoid fragmenting peculiar skbs in SACK 2017-05-11 21:35:20 -04:00
tcp_ipv4.c Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-05-10 10:30:46 -07:00
tcp_lp.c tcp: fix wraparound issue in tcp_lp 2017-05-02 15:07:02 -04:00
tcp_metrics.c treewide: use kv[mz]alloc* rather than opencoded variants 2017-05-08 17:15:13 -07:00
tcp_minisocks.c tcp: do not inherit fastopen_req from parent 2017-05-04 11:00:04 -04:00
tcp_nv.c
tcp_offload.c
tcp_output.c tcp: internal implementation for pacing 2017-05-16 15:43:31 -04:00
tcp_probe.c tcp: Revert "tcp: tcp_probe: use spin_lock_bh()" 2017-02-21 13:26:03 -05:00
tcp_rate.c tcp: do not pass timestamp to tcp_rate_gen() 2017-04-26 14:44:38 -04:00
tcp_recovery.c tcp: tcp_rack_reo_timeout() must update tp->tcp_mstamp 2017-04-27 11:46:15 -04:00
tcp_scalable.c
tcp_timer.c tcp: internal implementation for pacing 2017-05-16 15:43:31 -04:00
tcp_vegas.c
tcp_vegas.h
tcp_veno.c
tcp_westwood.c tcp_westwood: fix tcp_westwood_info() style mistakes 2017-03-16 20:23:28 -07:00
tcp_yeah.c
tcp.c tcp: fix access to sk->sk_state in tcp_poll() 2017-04-30 22:24:16 -04:00
tunnel4.c
udp_diag.c
udp_impl.h
udp_offload.c udp: disable inner UDP checksum offloads in IPsec case 2017-04-24 13:48:54 -04:00
udp_tunnel.c
udp.c udp: keep the sk_receive_queue held when splicing 2017-05-16 15:41:30 -04:00
udplite.c
xfrm4_input.c esp: Add a software GRO codepath 2017-02-15 11:04:11 +01:00
xfrm4_mode_beet.c
xfrm4_mode_transport.c xfrm: Add encapsulation header offsets while SKB is not encrypted 2017-04-14 10:07:39 +02:00
xfrm4_mode_tunnel.c xfrm: Add encapsulation header offsets while SKB is not encrypted 2017-04-14 10:07:39 +02:00
xfrm4_output.c xfrm: Add an IPsec hardware offloading API 2017-04-14 10:06:10 +02:00
xfrm4_policy.c xfrm: policy: make policy backend const 2017-02-09 10:22:19 +01:00
xfrm4_protocol.c xfrm: input: constify xfrm_input_afinfo 2017-02-09 10:22:17 +01:00
xfrm4_state.c
xfrm4_tunnel.c