linux/net/ipv4
Eric Dumazet 4e1fddc98d tcp_cubic: fix spurious Hystart ACK train detections for not-cwnd-limited flows
While testing BIG TCP patch series, I was expecting that TCP_RR workloads
with 80KB requests/answers would send one 80KB TSO packet,
then being received as a single GRO packet.

It turns out this was not happening, and the root cause was that
cubic Hystart ACK train was triggering after a few (2 or 3) rounds of RPC.

Hystart was wrongly setting CWND/SSTHRESH to 30, while my RPC
needed a budget of ~20 segments.

Ideally these TCP_RR flows should not exit slow start.

Cubic Hystart should reset itself at each round, instead of assuming
every TCP flow is a bulk one.

Note that even after this patch, Hystart can still trigger, depending
on scheduling artifacts, but at a higher CWND/SSTHRESH threshold,
keeping optimal TSO packet sizes.

Tested:

ip link set dev eth0 gro_ipv6_max_size 131072 gso_ipv6_max_size 131072
nstat -n; netperf -H ... -t TCP_RR  -l 5  -- -r 80000,80000 -K cubic; nstat|egrep "Ip6InReceives|Hystart|Ip6OutRequests"

Before:

   8605
Ip6InReceives                   87541              0.0
Ip6OutRequests                  129496             0.0
TcpExtTCPHystartTrainDetect     1                  0.0
TcpExtTCPHystartTrainCwnd       30                 0.0

After:

  8760
Ip6InReceives                   88514              0.0
Ip6OutRequests                  87975              0.0

Fixes: ae27e98a51 ("[TCP] CUBIC v2.3")
Co-developed-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Link: https://lore.kernel.org/r/20211123202535.1843771-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2021-11-24 17:26:05 -08:00
..
bpfilter net: Revert "net: optimize the sockptr_t for unified kernel/user address spaces" 2020-08-10 12:06:44 -07:00
netfilter Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf-next 2021-10-18 14:05:25 +01:00
af_inet.c net: introduce sk_forward_alloc_get() 2021-10-27 18:20:29 -07:00
ah4.c Networking changes for 5.14. 2021-06-30 15:51:09 -07:00
arp.c net: arp: introduce arp_evict_nocarrier sysctl parameter 2021-11-01 19:57:14 -07:00
bpf_tcp_ca.c bpf: Forbid bpf_ktime_get_coarse_ns and bpf_timer_* in tracing progs 2021-11-15 20:35:58 -08:00
cipso_ipv4.c NET: IPV4: fix error "do not initialise globals to 0" 2021-09-19 12:43:56 +01:00
datagram.c net/ipv4/datagram.c: remove superfluous header files from datagram.c 2021-09-29 11:39:33 +01:00
devinet.c net: return correct error code 2021-11-15 14:22:12 +00:00
esp4_offload.c xfrm: remove description from xfrm_type struct 2021-06-09 09:38:52 +02:00
esp4.c ipsec: Remove unneeded extra variable in esp4 esp_ssg_unref() 2021-07-20 16:14:23 +02:00
fib_frontend.c net: Use nlmsg_unicast() instead of netlink_unicast() 2021-07-13 09:28:29 -07:00
fib_lookup.h ipv4: Fix spelling mistakes 2021-06-07 14:08:30 -07:00
fib_notifier.c net: ipv4: remove superfluous header files from fib_notifier.c 2021-09-28 17:32:56 -07:00
fib_rules.c fib: use indirect call wrappers in the most common fib_rules_ops 2020-07-28 17:42:31 -07:00
fib_semantics.c net: ipv4: Fix rtnexthop len when RTA_FLOW is present 2021-09-24 14:07:10 +01:00
fib_trie.c memcg: enable accounting for IP address and routing-related objects 2021-07-20 06:00:38 -07:00
fou.c fou: remove sparse errors 2021-08-31 12:03:33 +01:00
gre_demux.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
gre_offload.c ip_gre: add csum offload support for gre header 2021-01-29 20:39:14 -08:00
icmp.c icmp: fix icmp_ext_echo_iio parsing in icmp_build_probe 2021-10-14 07:54:47 -07:00
igmp.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2021-08-13 06:41:22 -07:00
inet_connection_sock.c tcp: switch orphan_count to bare per-cpu counters 2021-10-15 11:28:34 +01:00
inet_diag.c net: introduce sk_forward_alloc_get() 2021-10-27 18:20:29 -07:00
inet_fragment.c inet: frags: batch fqdir destroy works 2020-12-12 15:08:54 -08:00
inet_hashtables.c tcp: switch orphan_count to bare per-cpu counters 2021-10-15 11:28:34 +01:00
inet_timewait_sock.c net: Use generic ns_common::count 2020-08-19 14:06:36 +02:00
inetpeer.c inetpeer: use div64_ul() and clamp_val() calculate inet_peer_threshold 2021-03-01 13:32:12 -08:00
ip_forward.c
ip_fragment.c
ip_gre.c ip: use dev_addr_set() in tunnels 2021-10-13 09:41:37 -07:00
ip_input.c net: use indirect call helpers for dst_input 2021-02-03 14:51:39 -08:00
ip_options.c net: clean up codestyle for net/ipv4 2020-08-25 06:28:02 -07:00
ip_output.c net: ipv4: Fix the warning for dereference 2021-08-30 12:47:09 +01:00
ip_sockglue.c ipv4: guard IP_MINTTL with a static key 2021-10-25 18:02:14 -07:00
ip_tunnel_core.c net: ip_tunnel: clean up endianness conversions 2021-01-08 19:25:35 -08:00
ip_tunnel.c ip: use dev_addr_set() in tunnels 2021-10-13 09:41:37 -07:00
ip_vti.c ip: use dev_addr_set() in tunnels 2021-10-13 09:41:37 -07:00
ipcomp.c Networking changes for 5.14. 2021-06-30 15:51:09 -07:00
ipconfig.c net: ipconfig: Release the rtnl_lock while waiting for carrier 2021-10-28 14:36:41 +01:00
ipip.c ip: use dev_addr_set() in tunnels 2021-10-13 09:41:37 -07:00
ipmr_base.c
ipmr.c ipmr: Fix indentation issue 2021-07-07 20:52:25 -07:00
Kconfig net: ipv4: remove duplicate "the the" phrase in Kconfig text 2020-08-18 16:02:16 -07:00
Makefile bpf: Clean up sockmap related Kconfigs 2021-02-26 12:28:03 -08:00
metrics.c treewide: rename nla_strlcpy to nla_strscpy. 2020-11-16 08:08:54 -08:00
netfilter.c netfilter: Dissect flow after packet mangling 2021-04-18 22:04:16 +02:00
netlink.c
nexthop.c net: nexthop: fix null pointer dereference when IPv6 is not enabled 2021-11-23 11:39:53 +00:00
ping.c Revert "Revert "ipv4: fix memory leaks in ip_cmsg_send() callers"" 2021-09-14 14:24:31 +01:00
proc.c tcp: switch orphan_count to bare per-cpu counters 2021-10-15 11:28:34 +01:00
protocol.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
raw_diag.c net: Use nlmsg_unicast() instead of netlink_unicast() 2021-07-13 09:28:29 -07:00
raw.c Revert "Revert "ipv4: fix memory leaks in ip_cmsg_send() callers"" 2021-09-14 14:24:31 +01:00
route.c net/ipv4/route.c: remove superfluous header files from route.c 2021-09-20 13:09:06 +01:00
syncookies.c net/ipv4/syncookies.c: remove superfluous header files from syncookies.c 2021-09-21 10:48:47 +01:00
sysctl_net_ipv4.c tcp: remove sk_{tr}x_skb_cache 2021-09-23 12:50:26 +01:00
tcp_bbr.c bpf: Enable TCP congestion control kfunc from modules 2021-10-05 17:07:41 -07:00
tcp_bic.c
tcp_bpf.c bpf, sockmap: Fix race in ingress receive verdict with redirect to self 2021-11-09 00:58:26 +01:00
tcp_cdg.c
tcp_cong.c net: Only allow init netns to set default tcp cong to a restricted algo 2021-05-04 11:58:28 -07:00
tcp_cubic.c tcp_cubic: fix spurious Hystart ACK train detections for not-cwnd-limited flows 2021-11-24 17:26:05 -08:00
tcp_dctcp.c bpf: Enable TCP congestion control kfunc from modules 2021-10-05 17:07:41 -07:00
tcp_dctcp.h
tcp_diag.c
tcp_fastopen.c net/ipv4/tcp_fastopen.c: remove superfluous header files from tcp_fastopen.c 2021-09-20 13:09:06 +01:00
tcp_highspeed.c Replace HTTP links with HTTPS ones: IPv* 2020-07-06 13:23:03 -07:00
tcp_htcp.c Replace HTTP links with HTTPS ones: IPv* 2020-07-06 13:23:03 -07:00
tcp_hybla.c
tcp_illinois.c
tcp_input.c tcp: adjust rcv_ssthresh according to sk_reserved_mem 2021-09-30 13:36:46 +01:00
tcp_ipv4.c ipv4: guard IP_MINTTL with a static key 2021-10-25 18:02:14 -07:00
tcp_lp.c ipv4: tcp_lp.c: Couple of typo fixes 2021-03-28 17:31:13 -07:00
tcp_metrics.c fixes-v5.11 2020-12-14 16:40:27 -08:00
tcp_minisocks.c net/ipv4/tcp_minisocks.c: remove superfluous header files from tcp_minisocks.c 2021-09-20 13:09:06 +01:00
tcp_nv.c net/ipv4/tcp_nv.c: remove superfluous header files from tcp_nv.c 2021-09-27 12:47:39 +01:00
tcp_offload.c net, gro: Set inner transport header offset in tcp/udp GRO hook 2021-08-02 10:20:56 +01:00
tcp_output.c tcp: Use BIT() for OPTION_* constants 2021-11-04 11:26:15 +00:00
tcp_rate.c tcp: tracking packets with CE marks in BW rate sample 2021-09-24 14:16:40 +01:00
tcp_recovery.c tcp: more accurately check DSACKs to grow RACK reordering window 2021-07-27 20:07:21 +01:00
tcp_scalable.c net: ipv4: delete repeated words 2020-08-24 17:31:20 -07:00
tcp_timer.c net: sock: introduce sk_error_report 2021-06-29 11:28:21 -07:00
tcp_ulp.c
tcp_vegas.c tcp: use semicolons rather than commas to separate statements 2020-10-13 17:11:52 -07:00
tcp_vegas.h
tcp_veno.c Replace HTTP links with HTTPS ones: IPv* 2020-07-06 13:23:03 -07:00
tcp_westwood.c
tcp_yeah.c tcp_yeah: check struct yeah size at compile time 2021-06-29 11:54:36 -07:00
tcp.c tcp: Fix uninitialized access in skb frags array for Rx 0cp. 2021-11-12 20:13:28 -08:00
tunnel4.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
udp_bpf.c net: Implement ->sock_is_readable() for UDP and AF_UNIX 2021-10-26 12:29:33 -07:00
udp_diag.c net: Use nlmsg_unicast() instead of netlink_unicast() 2021-07-13 09:28:29 -07:00
udp_impl.h net: pass a sockptr_t into ->setsockopt 2020-07-24 15:41:54 -07:00
udp_offload.c fou: remove sparse errors 2021-08-31 12:03:33 +01:00
udp_tunnel_core.c net/ipv4/udp_tunnel_core.c: remove superfluous header files from udp_tunnel_core.c 2021-09-21 10:17:20 +01:00
udp_tunnel_nic.c udp_tunnel: Fix udp_tunnel_nic work-queue type 2021-09-13 12:38:45 +01:00
udp_tunnel_stub.c udp_tunnel: add central NIC RX port offload infrastructure 2020-07-10 13:54:00 -07:00
udp.c udp: Validate checksum in udp_read_sock() 2021-11-16 13:18:23 +01:00
udplite.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
xfrm4_input.c xfrm: state: remove extract_input indirection from xfrm_state_afinfo 2020-05-06 09:40:08 +02:00
xfrm4_output.c xfrm: fix unused variable warning if CONFIG_NETFILTER=n 2020-05-11 15:12:27 +02:00
xfrm4_policy.c
xfrm4_protocol.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
xfrm4_state.c xfrm: remove output_finish indirection from xfrm_state_afinfo 2020-05-06 09:40:08 +02:00
xfrm4_tunnel.c net/ipv4/xfrm4_tunnel.c: remove superfluous header files from xfrm4_tunnel.c 2021-09-23 10:10:00 +02:00