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twx-linux/include/net
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Eric Dumazet 416dd649f3 tcp: add net.ipv4.tcp_comp_sack_rtt_percent 
TCP SACK compression has been added in 2018 in commit
5d9f4262b7ea ("tcp: add SACK compression").

It is working great for WAN flows (with large RTT).
Wifi in particular gets a significant boost _when_ ACK are suppressed.

Add a new sysctl so that we can tune the very conservative 5 % value
that has been used so far in this formula, so that small RTT flows
can benefit from this feature.

delay = min ( 5 % of RTT, 1 ms)

This patch adds new tcp_comp_sack_rtt_percent sysctl
to ease experiments and tuning.

Given that we cap the delay to 1ms (tcp_comp_sack_delay_ns sysctl),
set the default value to 33 %.

Quoting Neal Cardwell ( https://lore.kernel.org/netdev/CADVnQymZ1tFnEA1Q=vtECs0=Db7zHQ8=+WCQtnhHFVbEOzjVnQ@mail.gmail.com/ )

The rationale for 33% is basically to try to facilitate pipelining,
where there are always at least 3 ACKs and 3 GSO/TSO skbs per SRTT, so
that the path can maintain a budget for 3 full-sized GSO/TSO skbs "in
flight" at all times:

+ 1 skb in the qdisc waiting to be sent by the NIC next
+ 1 skb being sent by the NIC (being serialized by the NIC out onto the wire)
+ 1 skb being received and aggregated by the receiver machine's
aggregation mechanism (some combination of LRO, GRO, and sack
compression)

Note that this is basically the same magic number (3) and the same
rationales as:

(a) tcp_tso_should_defer() ensuring that we defer sending data for no
longer than cwnd/tcp_tso_win_divisor (where tcp_tso_win_divisor = 3),
and
(b) bbr_quantization_budget() ensuring that cwnd is at least 3 GSO/TSO
skbs to maintain pipelining and full throughput at low RTTs

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Link: https://patch.msgid.link/20251106115236.3450026-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2025-11-07 18:41:44 -08:00
..
9p netfs, 9p: Implement helpers for new write code 2024-05-01 18:07:37 +01:00
bluetooth Bluetooth: MGMT: Fix OOB access in parse_adv_monitor_pattern() 2025-10-31 12:43:05 -04:00
caif caif: Remove unused cfsrvl_getphyid 2024-10-08 15:33:49 -07:00
iucv net: reformat kdoc return statements 2024-12-09 14:44:59 -08:00
libeth xdp, libeth: make the xdp_init_buff() micro-optimization generic 2025-09-08 10:26:25 -07:00
mana net: mana: Support HW link state events 2025-10-31 15:56:53 -07:00
netfilter netfilter: fix typo in nf_conntrack_l4proto.h comment 2025-10-30 12:52:45 +01:00
netns tcp: add net.ipv4.tcp_comp_sack_rtt_percent 2025-11-07 18:41:44 -08:00
nfc net: nfc: nci: Increase NCI_DATA_TIMEOUT to 3000 ms 2025-09-03 17:02:12 -07:00
page_pool net: add helper to pre-check if PP for an Rx queue will be unreadable 2025-09-04 10:19:17 +02:00
phonet phonet: Convert phonet_routes.lock to spinlock_t. 2024-10-24 16:03:40 +02:00
psp net: psp: don't assume reply skbs will have a socket 2025-10-03 10:23:50 -07:00
sctp net: Convert proto_ops connect() callbacks to use sockaddr_unsized 2025-11-04 19:10:32 -08:00
tc_act net_sched: act_skbmod: use RCU in tcf_skbmod_dump() 2025-08-28 16:46:23 -07:00
6lowpan.h
act_api.h net_sched: act: remove tcfa_qstats 2025-09-02 15:52:24 -07:00
addrconf.h ipv6: Add in6_dev_rcu(). 2025-11-03 17:40:46 -08:00
af_ieee802154.h
af_rxrpc.h rxrpc: Remove deadcode 2025-04-24 17:03:45 -07:00
af_unix.h af_unix: Introduce SO_INQ. 2025-07-08 18:05:25 -07:00
af_vsock.h vsock: fix vsock_proto declaration 2025-07-07 16:55:54 -07:00
ah.h
aligned_data.h udp: move udp_memory_allocated into net_aligned_data 2025-07-02 14:22:02 -07:00
amt.h
arp.h neighbour: switch to standard rcu, instead of rcu_bh 2023-03-21 21:32:18 -07:00
atmclip.h
ax25.h ax25: Remove broken autobind 2025-03-24 10:26:53 +00:00
ax88796.h
bareudp.h
bond_3ad.h bonding: support aggregator selection based on port priority 2025-09-09 10:56:02 +02:00
bond_alb.h bonding: Correct spelling in headers 2024-08-26 09:37:22 -07:00
bond_options.h bonding: add support for per-port LACP actor priority 2025-09-09 10:56:02 +02:00
bonding.h Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-10-01 10:14:49 +02:00
bpf_sk_storage.h
busy_poll.h net: gro: decouple GRO from the NAPI layer 2025-02-27 14:03:14 +01:00
calipso.h move asm/unaligned.h to linux/unaligned.h 2024-10-02 17:23:23 -04:00
cfg80211-wext.h
cfg80211.h Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-11-06 09:27:40 -08:00
cfg802154.h mac802154: fix llsec key resources release in mac802154_llsec_key_del 2024-03-06 21:01:26 +01:00
checksum.h net: Fix checksum update for ILA adj-transport 2025-05-30 19:53:51 -07:00
cipso_ipv4.h move asm/unaligned.h to linux/unaligned.h 2024-10-02 17:23:23 -04:00
cls_cgroup.h net/cls_cgroup: Fix task_get_classid() during qdisc run 2025-09-14 11:55:04 -07:00
codel_impl.h
codel_qdisc.h
codel.h codel: fix kernel-doc notation warnings 2023-07-14 20:39:29 -07:00
compat.h
datalink.h net: datalink: Remove unused declarations 2023-07-27 17:17:32 -07:00
dcbevent.h
dcbnl.h
devlink.h devlink: Add a 'num_doorbells' driverinit param 2025-09-17 18:30:51 -07:00
dropreason-core.h tcp: add datapath logic for PSP with inline key exchange 2025-09-18 12:32:06 +02:00
dropreason.h wifi: mac80211: Drop cooked monitor support 2025-02-11 11:58:17 +01:00
dsa_stubs.h net: dsa: Use conduit and user terms 2023-10-24 13:08:14 -07:00
dsa.h net: dsa: add tagging driver for MaxLinear GSW1xx switch family 2025-11-06 14:16:17 -08:00
dscp.h net: add IEEE 802.1q specific helpers 2024-05-08 10:35:09 +01:00
dsfield.h
dst_cache.h net: Correct spelling in headers 2024-08-26 09:37:23 -07:00
dst_metadata.h net: dst_metadata: fix IP_DF bit not extracted from tunnel headers 2025-09-14 14:28:12 -07:00
dst_ops.h net: fix __dst_negative_advice() race 2024-05-29 17:34:49 -07:00
dst.h net: dst: introduce dst->dev_rcu 2025-08-29 19:36:31 -07:00
eee.h net: simplify eeecfg_mac_can_tx_lpi 2024-11-13 18:49:50 -08:00
erspan.h net: Correct spelling in headers 2024-08-26 09:37:23 -07:00
esp.h
espintcp.h inet: preserve const qualifier in inet_csk() 2024-04-01 21:27:08 -07:00
ethoc.h
failover.h
fib_notifier.h net: do not acquire rtnl in fib_seq_sum() 2024-10-11 15:35:05 -07:00
fib_rules.h net: fib_rules: Fix iif / oif matching on L3 master device 2025-04-15 17:54:56 -07:00
firewire.h
flow_dissector.h flow_dissector: cleanup FLOW_DISSECTOR_KEY_ENC_FLAGS 2024-07-15 09:14:39 -07:00
flow_offload.h net: sched: propagate "skip_sw" flag to struct flow_cls_common_offload 2024-10-30 17:33:53 -07:00
flow.h ipv4: Convert ->flowi4_tos to dscp_t. 2025-08-26 17:34:31 -07:00
fou.h bpf,fou: Add bpf_skb_{set,get}_fou_encap kfuncs 2023-04-12 16:40:39 -07:00
fq_impl.h
fq.h net: fq: Remove unused typedef fq_flow_get_default_t 2023-08-08 15:58:23 -07:00
garp.h
gen_stats.h
genetlink.h genetlink: fix typo in comment 2025-09-03 15:16:49 -07:00
geneve.h
gre.h ip_tunnel: convert __be16 tunnel flags to bitmaps 2024-04-01 10:49:28 +01:00
gro_cells.h
gro.h net: gro: remove unnecessary df checks 2025-09-25 12:42:49 +02:00
gso.h net: move gso declarations and functions to their own files 2023-06-10 00:11:41 -07:00
gtp.h gtp: properly parse extension headers 2024-05-07 01:35:55 +02:00
gue.h
handshake.h net/handshake: Add helpers for parsing incoming TLS Alerts 2023-07-28 14:07:59 -07:00
hotdata.h net: add NUMA awareness to skb_attempt_defer_free() 2025-09-30 15:45:53 +02:00
hwbm.h net: Correct spelling in headers 2024-08-26 09:37:23 -07:00
icmp.h ipv4: icmp: Pass IPv4 control block structure as an argument to __icmp_send() 2025-09-11 12:22:38 +02:00
ieee8021q.h net: add IEEE 802.1q specific helpers 2024-05-08 10:35:09 +01:00
ieee80211_radiotap.h wifi: mac80211: add RX flag to report radiotap VHT information 2025-10-30 08:38:51 +01:00
ieee802154_netdev.h mac802154: Handle association requests from peers 2023-11-20 11:43:03 +01:00
if_inet6.h ipv6: anycast: complete RCU handling of struct ifacaddr6 2024-02-26 18:40:34 -08:00
ife.h
inet6_connection_sock.h tcp/dccp: Remove inet_connection_sock_af_ops.addr2sockaddr(). 2025-03-24 12:10:13 -07:00
inet6_hashtables.h tcp: Remove inet6_hash(). 2025-09-22 11:38:43 -07:00
inet_common.h net: Convert proto callbacks from sockaddr to sockaddr_unsized 2025-11-04 19:10:33 -08:00
inet_connection_sock.h tcp: Remove timeout arg from reqsk_timeout(). 2025-11-07 18:05:26 -08:00
inet_dscp.h ipv4: Convert ->flowi4_tos to dscp_t. 2025-08-26 17:34:31 -07:00
inet_ecn.h
inet_frag.h inet: frags: change inet_frag_kill() to defer refcount updates 2025-03-18 13:18:36 +01:00
inet_hashtables.h tcp: Update bind bucket state on port release 2025-09-23 10:12:15 +02:00
inet_sock.h sctp: Remove sctp_copy_sock() and sctp_copy_descendant(). 2025-10-27 18:04:59 -07:00
inet_timewait_sock.h tcp: Update bind bucket state on port release 2025-09-23 10:12:15 +02:00
inetpeer.h inetpeer: remove create argument of inet_getpeer() 2024-12-17 19:37:00 -08:00
ioam6.h net: ioam6: multicast event 2024-02-28 11:19:41 +00:00
ip6_checksum.h
ip6_fib.h ipv6: Defer fib6_purge_rt() in fib6_add_rt2node() to fib6_add(). 2025-04-24 09:29:56 +02:00
ip6_route.h ipv6: make ipv6_pinfo.daddr_cache a boolean 2025-09-18 10:17:09 +02:00
ip6_tunnel.h ipv6: adopt skb_dst_dev() and skb_dst_dev_net[_rcu]() helpers 2025-07-02 14:32:30 -07:00
ip_fib.h ipv4: Convert ->flowi4_tos to dscp_t. 2025-08-26 17:34:31 -07:00
ip_tunnels.h net/ip6_tunnel: Prevent perpetual tunnel growth 2025-10-13 17:43:46 -07:00
ip_vs.h ipvs: Fix estimator kthreads preferred affinity 2025-08-13 08:34:33 +02:00
ip.h net: Convert proto callbacks from sockaddr to sockaddr_unsized 2025-11-04 19:10:33 -08:00
ipcomp.h xfrm: ipcomp: Use crypto_acomp interface 2025-03-21 17:36:49 +08:00
ipconfig.h
ipv6_frag.h inet: frags: change inet_frag_kill() to defer refcount updates 2025-03-18 13:18:36 +01:00
ipv6_stubs.h net: Convert proto callbacks from sockaddr to sockaddr_unsized 2025-11-04 19:10:33 -08:00
ipv6.h net: Convert proto callbacks from sockaddr to sockaddr_unsized 2025-11-04 19:10:33 -08:00
iw_handler.h Revert "wifi: cfg80211: unexport wireless_nlevent_flush()" 2024-10-09 08:53:01 +02:00
kcm.h net: kcm: Fix race condition in kcm_unattach() 2025-08-13 18:18:33 -07:00
l3mdev.h net: fib_rules: Fix iif / oif matching on L3 master device 2025-04-15 17:54:56 -07:00
lag.h
lapb.h net: lapb: increase LAPB_HEADER_LEN 2024-12-06 17:43:08 -08:00
llc_c_ac.h net: llc: Remove unused function declarations 2023-08-04 15:33:17 -07:00
llc_c_ev.h net: llc: Remove unused function declarations 2023-08-04 15:33:17 -07:00
llc_c_st.h llc: Constify struct llc_conn_state_trans 2024-07-15 08:51:01 -07:00
llc_conn.h llc: Check netns in llc_estab_match() and llc_listener_match(). 2023-07-20 10:46:28 +02:00
llc_if.h
llc_pdu.h net: Correct spelling in headers 2024-08-26 09:37:23 -07:00
llc_s_ac.h
llc_s_ev.h
llc_s_st.h llc: Constify struct llc_sap_state_trans 2024-07-15 08:51:19 -07:00
llc_sap.h
llc.h
lwtunnel.h net: dst: annotate data-races around dst->output 2025-07-02 14:32:30 -07:00
mac80211.h wifi: mac80211: add RX flag to report radiotap VHT information 2025-10-30 08:38:51 +01:00
mac802154.h move asm/unaligned.h to linux/unaligned.h 2024-10-02 17:23:23 -04:00
macsec.h net: macsec: Add endianness annotations in salt struct 2025-01-20 12:20:42 +00:00
mctp.h net: mctp: Allow limiting binds to a peer address 2025-07-15 12:08:39 +02:00
mctpdevice.h net: mctp: Expose transport binding identifier via IFLA attribute 2024-11-09 09:04:54 -08:00
mip6.h
mld.h
mpls_iptunnel.h
mpls.h
mptcp.h mptcp: sched: remove mptcp_sched_data 2025-04-15 08:21:46 -07:00
mrp.h
ncsi.h
ndisc.h net: replace ND_PRINTK with dynamic debug 2025-07-10 15:27:32 -07:00
neighbour_tables.h neighbour: Create netdev->neighbour association 2024-11-09 13:22:57 -08:00
neighbour.h neighbour: Convert rwlock of struct neigh_table to spinlock. 2025-10-24 17:57:20 -07:00
net_debug.h Kbuild updates for v6.13 2024-11-30 13:41:50 -08:00
net_failover.h
net_namespace.h namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
net_ratelimit.h
net_shaper.h net-shapers: implement NL get operation 2024-10-10 08:30:22 -07:00
net_trackers.h
netdev_lock.h Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-05-22 09:42:41 -07:00
netdev_netlink.h net: add granular lock for the netdev netlink socket 2025-03-12 13:32:35 -07:00
netdev_queues.h net: add helper to pre-check if PP for an Rx queue will be unreadable 2025-09-04 10:19:17 +02:00
netdev_rx_queue.h net: designate XSK pool pointers in queues as "ops protected" 2025-04-09 17:01:51 -07:00
netevent.h
netkit.h bpf, netkit: Add indirect call wrapper for fetching peer dev 2023-11-20 10:15:16 -08:00
netlabel.h Networking changes for 6.13. 2024-11-21 08:28:08 -08:00
netlink.h netlink: introduce type-checking attribute iteration for nlmsg 2025-07-02 15:39:04 -07:00
netmem.h net: netmem: remove NET_IOV_MAX from net_iov_type enum 2025-10-28 17:41:46 -07:00
netprio_cgroup.h
netrom.h
nexthop.h ipv6: Protect nh->f6i_list with spinlock and flag. 2025-04-24 09:29:56 +02:00
nl802154.h nl802154: fix some kernel-doc warnings 2025-10-20 17:13:40 -07:00
nsh.h net: NSH: fix kernel-doc notation warning 2023-07-14 20:39:29 -07:00
pfcp.h net: pfcp: fix typo in message_priority field name 2025-06-13 18:17:08 -07:00
pie.h pie: fix kernel-doc notation warning 2023-07-14 20:39:30 -07:00
ping.h net: Convert proto callbacks from sockaddr to sockaddr_unsized 2025-11-04 19:10:33 -08:00
pkt_cls.h net: sched: refine software bypass handling in tc_run 2025-01-20 09:21:27 +00:00
pkt_sched.h net/sched: Remove unused typedef psched_tdiff_t 2025-10-27 18:05:54 -07:00
pptp.h
proto_memory.h net: Allow opt-out from global protocol memory accounting. 2025-10-16 12:04:47 -07:00
protocol.h ipv6: move tcp_ipv6_hash_secret and udp_ipv6_hash_secret to net_hotdata 2024-03-07 21:12:43 -08:00
psample.h net: psample: fix flag being set in wrong skb 2024-07-11 18:11:31 -07:00
psnap.h
psp.h psp: base PSP device support 2025-09-18 12:32:06 +02:00
raw.h net: use NUMA drop counters for softnet_data.dropped 2025-09-14 11:35:17 -07:00
rawv6.h ipv6: raw: constify raw_v6_match() socket argument 2023-03-17 08:56:37 +00:00
red.h net: sched: Correct spelling in headers 2024-08-26 09:37:23 -07:00
regulatory.h net: Correct spelling in headers 2024-08-26 09:37:23 -07:00
request_sock.h tcp: Call tcp_syn_ack_timeout() directly. 2025-11-07 18:05:25 -08:00
rose.h net: rose: convert 'use' field to refcount_t 2025-08-27 07:43:08 -07:00
route.h net: use dst_dev_rcu() in sk_setup_caps() 2025-08-29 19:36:32 -07:00
rpl.h ipv6: rpl: Remove pskb(_may)?_pull() in ipv6_rpl_srh_rcv(). 2023-06-19 11:32:58 -07:00
rps.h net: Add rfs_needed() helper 2025-09-03 15:08:20 -07:00
rsi_91x.h rsi: remove kernel-doc comment marker 2023-07-14 20:39:30 -07:00
rstreason.h net: Retire DCCP socket. 2025-04-11 18:58:10 -07:00
rtnetlink.h rtnetlink: Remove "net" from newlink params 2025-02-21 15:28:03 -08:00
rtnh.h
sch_generic.h net: dev_queue_xmit() llist adoption 2025-10-16 16:25:10 -07:00
scm.h af_unix/scm: fix whitespace errors 2025-07-04 09:32:35 +02:00
secure_seq.h net: Retire DCCP socket. 2025-04-11 18:58:10 -07:00
seg6_hmac.h ipv6: sr: Prepare HMAC key ahead of time 2025-08-26 18:11:29 -07:00
seg6_local.h seg6: Use nested-BH locking for seg6_bpf_srh_states. 2024-06-24 16:41:23 -07:00
seg6.h ipv6: sr: restruct ifdefines 2024-05-30 18:29:38 -07:00
selftests.h net: selftests: export packet creation helpers for driver use 2025-11-06 13:38:11 +01:00
slhc_vj.h
smc.h dibs: Move event handling to dibs layer 2025-09-23 11:13:22 +02:00
snmp.h net: snmp: remove SNMP_MIB_SENTINEL 2025-09-08 18:06:21 -07:00
sock_reuseport.h net: core: annotate socks of struct sock_reuseport with __counted_by 2024-08-02 17:16:59 -07:00
sock.h net: Convert proto callbacks from sockaddr to sockaddr_unsized 2025-11-04 19:10:33 -08:00
Space.h net: appletalk: remove cops support 2023-10-04 11:49:20 -07:00
stp.h
strparser.h strparser: Remove unused __strp_unpause 2025-05-05 16:48:12 -07:00
switchdev.h net: bridge: switchdev: Skip MDB replays of deferred events on offload 2024-02-16 09:36:37 +00:00
tc_wrapper.h Merge branch 'x86/bugs' into x86/core, to pick up pending changes before dependent patches 2024-02-14 10:49:37 +01:00
tcp_ao.h tcp: Free TCP-AO/TCP-MD5 info/keys without RCU 2025-09-11 19:05:56 -07:00
tcp_ecn.h tcp: accecn: AccECN option failure handling 2025-09-18 08:47:52 +02:00
tcp_states.h tcp: Dump bound-only sockets in inet_diag. 2023-12-04 14:45:26 -08:00
tcp.h tcp: Apply max RTO to non-TFO SYN+ACK. 2025-11-07 18:05:26 -08:00
tcx.h bpf: Remove location field in tcx_link 2025-07-11 11:00:57 -07:00
timewait_sock.h tcp: Remove timewait_sock_ops.twsk_destructor(). 2025-08-25 17:53:35 -07:00
tipc.h
tls_prot.h net/tls: Add TLS Alert definitions 2023-07-28 14:07:59 -07:00
tls_toe.h
tls.h Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-10-31 06:46:03 -07:00
transp_v6.h inet6: Remove unused function declaration udpv6_connect() 2023-08-01 15:06:27 -07:00
tso.h
tun_proto.h
udp_tunnel.h udp_tunnel: fix deadlock in udp_tunnel_nic_set_port_priv() 2025-06-24 16:31:36 -07:00
udp.h net: Convert proto callbacks from sockaddr to sockaddr_unsized 2025-11-04 19:10:33 -08:00
udplite.h udplite: fix various data-races 2023-09-14 16:16:36 +02:00
vsock_addr.h net: Convert proto_ops connect() callbacks to use sockaddr_unsized 2025-11-04 19:10:32 -08:00
vxlan.h vxlan: Support MC routing in the underlay 2025-06-17 18:18:46 -07:00
wext.h
x25.h net/x25: Remove unused x25_terminate_link() 2025-07-14 17:19:13 -07:00
x25device.h
xdp_priv.h
xdp_sock_drv.h xsk: Move NETDEV_XDP_ACT_ZC into generic header 2025-11-06 16:46:11 -08:00
xdp_sock.h net: xsk: introduce XDP_MAX_TX_SKB_BUDGET setsockopt 2025-07-10 14:48:29 +02:00
xdp.h bpf-next-for-netdev 2025-09-24 10:22:37 -07:00
xfrm.h Revert "xfrm: destroy xfrm_state synchronously on net exit path" 2025-07-08 13:28:29 +02:00
xsk_buff_pool.h xsk: use a smaller new lock for shared pool case 2025-11-04 16:10:53 +01:00