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0cef6a4c34
linux/net/ipv4
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Eric Dumazet 0cef6a4c34 tcp: give prequeue mode some care 
TCP prequeue goal is to defer processing of incoming packets
to user space thread currently blocked in a recvmsg() system call.

Intent is to spend less time processing these packets on behalf
of softirq handler, as softirq handler is unfair to normal process
scheduler decisions, as it might interrupt threads that do not
even use networking.

Current prequeue implementation has following issues :

1) It only checks size of the prequeue against sk_rcvbuf

   It was fine 15 years ago when sk_rcvbuf was in the 64KB vicinity.
   But we now have ~8MB values to cope with modern networking needs.
   We have to add sk_rmem_alloc in the equation, since out of order
   packets can definitely use up to sk_rcvbuf memory themselves.

2) Even with a fixed memory truesize check, prequeue can be filled
   by thousands of packets. When prequeue needs to be flushed, either
   from sofirq context (in tcp_prequeue() or timer code), or process
   context (in tcp_prequeue_process()), this adds a latency spike
   which is often not desirable.
   I added a fixed limit of 32 packets, as this translated to a max
   flush time of 60 us on my test hosts.

   Also note that all packets in prequeue are not accounted for tcp_mem,
   since they are not charged against sk_forward_alloc at this point.
   This is probably not a big deal.

Note that this might increase LINUX_MIB_TCPPREQUEUEDROPPED counts,
which is misnamed, as packets are not dropped at all, but rather pushed
to the stack (where they can be either consumed or dropped)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-04-28 17:14:35 -04:00
..
netfilter Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf-next 2016-04-24 00:12:08 -04:00
af_inet.c GSO: Support partial segmentation offload 2016-04-14 16:23:41 -04:00
ah4.c ah4: Fix error return in ah_input(). 2015-08-25 13:38:50 -07:00
arp.c net: rename NET_{ADD|INC}_STATS_BH() 2016-04-27 22:48:24 -04:00
cipso_ipv4.c net: introduce lockdep_is_held and update various places to use it 2016-04-07 16:44:14 -04:00
datagram.c net: Set sk_txhash from a random number 2015-07-29 22:44:04 -07:00
devinet.c ipv4: Don't do expensive useless work during inetdev destroy. 2016-03-13 23:28:35 -04:00
esp4.c esp4: Switch to new AEAD interface 2015-05-28 11:23:20 +08:00
fib_frontend.c ipv4/fib: don't warn when primary address is missing if in_dev is dead 2016-04-24 23:26:29 -04:00
fib_lookup.h ipv4: consider TOS in fib_select_default 2015-07-24 22:46:11 -07:00
fib_rules.c net: ipv6: use common fib_default_rule_pref 2015-09-09 14:19:50 -07:00
fib_semantics.c net: ipv4: Consider failed nexthops in multipath routes 2016-04-11 15:16:13 -04:00
fib_trie.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-02-01 15:56:08 -08:00
fou.c ip_tunnel_core: iptunnel_handle_offloads returns int and doesn't free skb 2016-04-16 19:09:13 -04:00
gre_demux.c gre: Remove support for sharing GRE protocol hook. 2015-08-10 14:03:54 -07:00
gre_offload.c GRE: Add support for GRO/GSO of IPv6 GRE traffic 2016-04-16 19:09:13 -04:00
icmp.c net: icmp: rename ICMPMSGIN_INC_STATS_BH() 2016-04-27 22:48:23 -04:00
igmp.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-03-08 12:34:12 -05:00
inet_connection_sock.c net: rename IP_INC_STATS_BH() 2016-04-27 22:48:23 -04:00
inet_diag.c sock_diag: align nlattr properly when needed 2016-04-26 12:00:48 -04:00
inet_fragment.c inet: kill unused skb_free op 2016-01-05 22:25:57 -05:00
inet_hashtables.c net: rename NET_{ADD|INC}_STATS_BH() 2016-04-27 22:48:24 -04:00
inet_timewait_sock.c net: rename NET_{ADD|INC}_STATS_BH() 2016-04-27 22:48:24 -04:00
inetpeer.c net: Add helper function to compare inetpeer addresses 2015-08-28 13:32:36 -07:00
ip_forward.c net: rename IP_ADD_STATS_BH() 2016-04-27 22:48:24 -04:00
ip_fragment.c net: rename IP_INC_STATS_BH() 2016-04-27 22:48:23 -04:00
ip_gre.c ip_tunnel_core: iptunnel_handle_offloads returns int and doesn't free skb 2016-04-16 19:09:13 -04:00
ip_input.c net: rename NET_{ADD|INC}_STATS_BH() 2016-04-27 22:48:24 -04:00
ip_options.c net: ipv4: Convert IP network timestamps to be y2038 safe 2016-03-01 17:18:44 -05:00
ip_output.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-03-08 12:34:12 -05:00
ip_sockglue.c net: better drop monitoring in ip{6}_recv_error() 2016-04-25 15:48:10 -04:00
ip_tunnel_core.c libnl: nla_put_be64(): align on a 64-bit area 2016-04-23 20:13:24 -04:00
ip_tunnel.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-03-08 12:34:12 -05:00
ip_vti.c ip_tunnel: Move stats update to iptunnel_xmit() 2015-12-25 23:32:23 -05:00
ipcomp.c ipv4: coding style: comparison for equality with NULL 2015-04-03 12:11:15 -04:00
ipconfig.c ipv4: ipconfig: avoid unused ic_proto_used symbol 2016-01-29 19:39:09 -08:00
ipip.c ip_tunnel_core: iptunnel_handle_offloads returns int and doesn't free skb 2016-04-16 19:09:13 -04:00
ipmr.c ipmr: align RTA_MFC_STATS on 64-bit 2016-04-21 14:22:13 -04:00
Kconfig ipv4: Remove inet_lro library 2016-02-17 16:15:46 -05:00
Makefile ipv4: Remove inet_lro library 2016-02-17 16:15:46 -05:00
netfilter.c ipv4: Pass struct net into ip_route_me_harder 2015-09-29 20:21:32 +02:00
ping.c sock: enable timestamping using control messages 2016-04-04 15:50:30 -04:00
proc.c ipv4: Namespaceify ip_default_ttl sysctl knob 2016-02-16 20:42:54 -05:00
protocol.c net: Export inet_offloads and inet6_offloads 2014-09-19 17:15:31 -04:00
raw.c sock: enable timestamping using control messages 2016-04-04 15:50:30 -04:00
route.c net: rename IP_INC_STATS_BH() 2016-04-27 22:48:23 -04:00
syncookies.c net: rename NET_{ADD|INC}_STATS_BH() 2016-04-27 22:48:24 -04:00
sysctl_net_ipv4.c net: ipv4: Consider failed nexthops in multipath routes 2016-04-11 15:16:13 -04:00
tcp_bic.c tcp: add tcp_in_slow_start helper 2015-07-09 14:22:52 -07:00
tcp_cdg.c net: rename NET_{ADD|INC}_STATS_BH() 2016-04-27 22:48:24 -04:00
tcp_cong.c tcp: remove tcp_ecn_make_synack() socket argument 2015-09-25 13:00:38 -07:00
tcp_cubic.c net: rename NET_{ADD|INC}_STATS_BH() 2016-04-27 22:48:24 -04:00
tcp_dctcp.c tcp: allow dctcp alpha to drop to zero 2015-10-23 02:46:52 -07:00
tcp_diag.c net: diag: Support destroying TCP sockets. 2015-12-15 23:26:52 -05:00
tcp_fastopen.c net: rename NET_{ADD|INC}_STATS_BH() 2016-04-27 22:48:24 -04:00
tcp_highspeed.c tcp: add tcp_in_slow_start helper 2015-07-09 14:22:52 -07:00
tcp_htcp.c tcp: add tcp_in_slow_start helper 2015-07-09 14:22:52 -07:00
tcp_hybla.c tcp: do not slow start when cwnd equals ssthresh 2015-07-09 14:22:52 -07:00
tcp_illinois.c tcp: add tcp_in_slow_start helper 2015-07-09 14:22:52 -07:00
tcp_input.c tcp: Handle eor bit when coalescing skb 2016-04-28 16:14:19 -04:00
tcp_ipv4.c tcp: give prequeue mode some care 2016-04-28 17:14:35 -04:00
tcp_lp.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_metrics.c libnl: nla_put_msecs(): align on a 64-bit area 2016-04-23 20:13:24 -04:00
tcp_minisocks.c net: rename NET_{ADD|INC}_STATS_BH() 2016-04-27 22:48:24 -04:00
tcp_offload.c GSO: Support partial segmentation offload 2016-04-14 16:23:41 -04:00
tcp_output.c tcp: Handle eor bit when fragmenting a skb 2016-04-28 16:14:19 -04:00
tcp_probe.c net: ipv4: tcp_probe: Replace timespec with timespec64 2016-03-01 17:18:44 -05:00
tcp_recovery.c net: rename NET_{ADD|INC}_STATS_BH() 2016-04-27 22:48:24 -04:00
tcp_scalable.c tcp: add tcp_in_slow_start helper 2015-07-09 14:22:52 -07:00
tcp_timer.c net: rename NET_{ADD|INC}_STATS_BH() 2016-04-27 22:48:24 -04:00
tcp_vegas.c tcp: add tcp_in_slow_start helper 2015-07-09 14:22:52 -07:00
tcp_vegas.h tcp: prepare CC get_info() access from getsockopt() 2015-04-29 17:10:38 -04:00
tcp_veno.c tcp: add tcp_in_slow_start helper 2015-07-09 14:22:52 -07:00
tcp_westwood.c tcp_westwood: fix tcp_westwood_info() 2015-05-05 19:50:09 -04:00
tcp_yeah.c tcp_yeah: don't set ssthresh below 2 2016-01-11 17:25:16 -05:00
tcp.c tcp: Make use of MSG_EOR in tcp_sendmsg 2016-04-28 16:14:18 -04:00
tunnel4.c
udp_diag.c udp: no longer use SLAB_DESTROY_BY_RCU 2016-04-04 22:11:19 -04:00
udp_impl.h net: Remove iocb argument from sendmsg and recvmsg 2015-03-02 13:06:31 -05:00
udp_offload.c GSO: Support partial segmentation offload 2016-04-14 16:23:41 -04:00
udp_tunnel.c udp: Add socket based GRO and config 2016-04-07 16:53:29 -04:00
udp.c net: udp: rename UDP_INC_STATS_BH() 2016-04-27 22:48:23 -04:00
udplite.c net: Eliminate no_check from protosw 2014-05-23 16:28:53 -04:00
xfrm4_input.c netfilter: Pass net into okfn 2015-09-17 17:18:37 -07:00
xfrm4_mode_beet.c ipv4: ERROR: code indent should use tabs where possible 2013-12-26 13:43:21 -05:00
xfrm4_mode_transport.c
xfrm4_mode_tunnel.c ipv4: hash net ptr into fragmentation bucket selection 2015-03-25 14:07:04 -04:00
xfrm4_output.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2015-10-24 06:54:12 -07:00
xfrm4_policy.c Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec 2015-12-22 16:26:31 -05:00
xfrm4_protocol.c xfrm4: Remove duplicate semicolon 2014-06-30 07:49:47 +02:00
xfrm4_state.c inet: make no_pmtu_disc per namespace and kill ipv4_config 2013-12-18 16:58:20 -05:00
xfrm4_tunnel.c