1. 09 5月, 2014 2 次提交
  2. 14 1月, 2014 1 次提交
    • H
      ipv4: introduce ip_dst_mtu_maybe_forward and protect forwarding path against pmtu spoofing · f87c10a8
      Hannes Frederic Sowa 提交于
      While forwarding we should not use the protocol path mtu to calculate
      the mtu for a forwarded packet but instead use the interface mtu.
      
      We mark forwarded skbs in ip_forward with IPSKB_FORWARDED, which was
      introduced for multicast forwarding. But as it does not conflict with
      our usage in unicast code path it is perfect for reuse.
      
      I moved the functions ip_sk_accept_pmtu, ip_sk_use_pmtu and ip_skb_dst_mtu
      along with the new ip_dst_mtu_maybe_forward to net/ip.h to fix circular
      dependencies because of IPSKB_FORWARDED.
      
      Because someone might have written a software which does probe
      destinations manually and expects the kernel to honour those path mtus
      I introduced a new per-namespace "ip_forward_use_pmtu" knob so someone
      can disable this new behaviour. We also still use mtus which are locked on a
      route for forwarding.
      
      The reason for this change is, that path mtus information can be injected
      into the kernel via e.g. icmp_err protocol handler without verification
      of local sockets. As such, this could cause the IPv4 forwarding path to
      wrongfully emit fragmentation needed notifications or start to fragment
      packets along a path.
      
      Tunnel and ipsec output paths clear IPCB again, thus IPSKB_FORWARDED
      won't be set and further fragmentation logic will use the path mtu to
      determine the fragmentation size. They also recheck packet size with
      help of path mtu discovery and report appropriate errors.
      
      Cc: Eric Dumazet <eric.dumazet@gmail.com>
      Cc: David Miller <davem@davemloft.net>
      Cc: John Heffner <johnwheffner@gmail.com>
      Cc: Steffen Klassert <steffen.klassert@secunet.com>
      Signed-off-by: NHannes Frederic Sowa <hannes@stressinduktion.org>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      f87c10a8
  3. 27 12月, 2013 1 次提交
  4. 19 12月, 2013 1 次提交
  5. 07 12月, 2013 1 次提交
    • E
      tcp: auto corking · f54b3111
      Eric Dumazet 提交于
      With the introduction of TCP Small Queues, TSO auto sizing, and TCP
      pacing, we can implement Automatic Corking in the kernel, to help
      applications doing small write()/sendmsg() to TCP sockets.
      
      Idea is to change tcp_push() to check if the current skb payload is
      under skb optimal size (a multiple of MSS bytes)
      
      If under 'size_goal', and at least one packet is still in Qdisc or
      NIC TX queues, set the TCP Small Queue Throttled bit, so that the push
      will be delayed up to TX completion time.
      
      This delay might allow the application to coalesce more bytes
      in the skb in following write()/sendmsg()/sendfile() system calls.
      
      The exact duration of the delay is depending on the dynamics
      of the system, and might be zero if no packet for this flow
      is actually held in Qdisc or NIC TX ring.
      
      Using FQ/pacing is a way to increase the probability of
      autocorking being triggered.
      
      Add a new sysctl (/proc/sys/net/ipv4/tcp_autocorking) to control
      this feature and default it to 1 (enabled)
      
      Add a new SNMP counter : nstat -a | grep TcpExtTCPAutoCorking
      This counter is incremented every time we detected skb was under used
      and its flush was deferred.
      
      Tested:
      
      Interesting effects when using line buffered commands under ssh.
      
      Excellent performance results in term of cpu usage and total throughput.
      
      lpq83:~# echo 1 >/proc/sys/net/ipv4/tcp_autocorking
      lpq83:~# perf stat ./super_netperf 4 -t TCP_STREAM -H lpq84 -- -m 128
      9410.39
      
       Performance counter stats for './super_netperf 4 -t TCP_STREAM -H lpq84 -- -m 128':
      
            35209.439626 task-clock                #    2.901 CPUs utilized
                   2,294 context-switches          #    0.065 K/sec
                     101 CPU-migrations            #    0.003 K/sec
                   4,079 page-faults               #    0.116 K/sec
          97,923,241,298 cycles                    #    2.781 GHz                     [83.31%]
          51,832,908,236 stalled-cycles-frontend   #   52.93% frontend cycles idle    [83.30%]
          25,697,986,603 stalled-cycles-backend    #   26.24% backend  cycles idle    [66.70%]
         102,225,978,536 instructions              #    1.04  insns per cycle
                                                   #    0.51  stalled cycles per insn [83.38%]
          18,657,696,819 branches                  #  529.906 M/sec                   [83.29%]
              91,679,646 branch-misses             #    0.49% of all branches         [83.40%]
      
            12.136204899 seconds time elapsed
      
      lpq83:~# echo 0 >/proc/sys/net/ipv4/tcp_autocorking
      lpq83:~# perf stat ./super_netperf 4 -t TCP_STREAM -H lpq84 -- -m 128
      6624.89
      
       Performance counter stats for './super_netperf 4 -t TCP_STREAM -H lpq84 -- -m 128':
            40045.864494 task-clock                #    3.301 CPUs utilized
                     171 context-switches          #    0.004 K/sec
                      53 CPU-migrations            #    0.001 K/sec
                   4,080 page-faults               #    0.102 K/sec
         111,340,458,645 cycles                    #    2.780 GHz                     [83.34%]
          61,778,039,277 stalled-cycles-frontend   #   55.49% frontend cycles idle    [83.31%]
          29,295,522,759 stalled-cycles-backend    #   26.31% backend  cycles idle    [66.67%]
         108,654,349,355 instructions              #    0.98  insns per cycle
                                                   #    0.57  stalled cycles per insn [83.34%]
          19,552,170,748 branches                  #  488.244 M/sec                   [83.34%]
             157,875,417 branch-misses             #    0.81% of all branches         [83.34%]
      
            12.130267788 seconds time elapsed
      Signed-off-by: NEric Dumazet <edumazet@google.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      f54b3111
  6. 05 11月, 2013 1 次提交
    • Y
      tcp: properly handle stretch acks in slow start · 9f9843a7
      Yuchung Cheng 提交于
      Slow start now increases cwnd by 1 if an ACK acknowledges some packets,
      regardless the number of packets. Consequently slow start performance
      is highly dependent on the degree of the stretch ACKs caused by
      receiver or network ACK compression mechanisms (e.g., delayed-ACK,
      GRO, etc).  But slow start algorithm is to send twice the amount of
      packets of packets left so it should process a stretch ACK of degree
      N as if N ACKs of degree 1, then exits when cwnd exceeds ssthresh. A
      follow up patch will use the remainder of the N (if greater than 1)
      to adjust cwnd in the congestion avoidance phase.
      
      In addition this patch retires the experimental limited slow start
      (LSS) feature. LSS has multiple drawbacks but questionable benefit. The
      fractional cwnd increase in LSS requires a loop in slow start even
      though it's rarely used. Configuring such an increase step via a global
      sysctl on different BDPS seems hard. Finally and most importantly the
      slow start overshoot concern is now better covered by the Hybrid slow
      start (hystart) enabled by default.
      Signed-off-by: NYuchung Cheng <ycheng@google.com>
      Signed-off-by: NNeal Cardwell <ncardwell@google.com>
      Signed-off-by: NEric Dumazet <edumazet@google.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      9f9843a7
  7. 22 10月, 2013 4 次提交
  8. 20 10月, 2013 1 次提交
  9. 01 10月, 2013 1 次提交
  10. 30 8月, 2013 1 次提交
    • E
      tcp: TSO packets automatic sizing · 95bd09eb
      Eric Dumazet 提交于
      After hearing many people over past years complaining against TSO being
      bursty or even buggy, we are proud to present automatic sizing of TSO
      packets.
      
      One part of the problem is that tcp_tso_should_defer() uses an heuristic
      relying on upcoming ACKS instead of a timer, but more generally, having
      big TSO packets makes little sense for low rates, as it tends to create
      micro bursts on the network, and general consensus is to reduce the
      buffering amount.
      
      This patch introduces a per socket sk_pacing_rate, that approximates
      the current sending rate, and allows us to size the TSO packets so
      that we try to send one packet every ms.
      
      This field could be set by other transports.
      
      Patch has no impact for high speed flows, where having large TSO packets
      makes sense to reach line rate.
      
      For other flows, this helps better packet scheduling and ACK clocking.
      
      This patch increases performance of TCP flows in lossy environments.
      
      A new sysctl (tcp_min_tso_segs) is added, to specify the
      minimal size of a TSO packet (default being 2).
      
      A follow-up patch will provide a new packet scheduler (FQ), using
      sk_pacing_rate as an input to perform optional per flow pacing.
      
      This explains why we chose to set sk_pacing_rate to twice the current
      rate, allowing 'slow start' ramp up.
      
      sk_pacing_rate = 2 * cwnd * mss / srtt
      
      v2: Neal Cardwell reported a suspect deferring of last two segments on
      initial write of 10 MSS, I had to change tcp_tso_should_defer() to take
      into account tp->xmit_size_goal_segs
      Signed-off-by: NEric Dumazet <edumazet@google.com>
      Cc: Neal Cardwell <ncardwell@google.com>
      Cc: Yuchung Cheng <ycheng@google.com>
      Cc: Van Jacobson <vanj@google.com>
      Cc: Tom Herbert <therbert@google.com>
      Acked-by: NYuchung Cheng <ycheng@google.com>
      Acked-by: NNeal Cardwell <ncardwell@google.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      95bd09eb
  11. 25 7月, 2013 1 次提交
    • E
      tcp: TCP_NOTSENT_LOWAT socket option · c9bee3b7
      Eric Dumazet 提交于
      Idea of this patch is to add optional limitation of number of
      unsent bytes in TCP sockets, to reduce usage of kernel memory.
      
      TCP receiver might announce a big window, and TCP sender autotuning
      might allow a large amount of bytes in write queue, but this has little
      performance impact if a large part of this buffering is wasted :
      
      Write queue needs to be large only to deal with large BDP, not
      necessarily to cope with scheduling delays (incoming ACKS make room
      for the application to queue more bytes)
      
      For most workloads, using a value of 128 KB or less is OK to give
      applications enough time to react to POLLOUT events in time
      (or being awaken in a blocking sendmsg())
      
      This patch adds two ways to set the limit :
      
      1) Per socket option TCP_NOTSENT_LOWAT
      
      2) A sysctl (/proc/sys/net/ipv4/tcp_notsent_lowat) for sockets
      not using TCP_NOTSENT_LOWAT socket option (or setting a zero value)
      Default value being UINT_MAX (0xFFFFFFFF), meaning this has no effect.
      
      This changes poll()/select()/epoll() to report POLLOUT
      only if number of unsent bytes is below tp->nosent_lowat
      
      Note this might increase number of sendmsg()/sendfile() calls
      when using non blocking sockets,
      and increase number of context switches for blocking sockets.
      
      Note this is not related to SO_SNDLOWAT (as SO_SNDLOWAT is
      defined as :
       Specify the minimum number of bytes in the buffer until
       the socket layer will pass the data to the protocol)
      
      Tested:
      
      netperf sessions, and watching /proc/net/protocols "memory" column for TCP
      
      With 200 concurrent netperf -t TCP_STREAM sessions, amount of kernel memory
      used by TCP buffers shrinks by ~55 % (20567 pages instead of 45458)
      
      lpq83:~# echo -1 >/proc/sys/net/ipv4/tcp_notsent_lowat
      lpq83:~# (super_netperf 200 -t TCP_STREAM -H remote -l 90 &); sleep 60 ; grep TCP /proc/net/protocols
      TCPv6     1880      2   45458   no     208   yes  ipv6        y  y  y  y  y  y  y  y  y  y  y  y  y  n  y  y  y  y  y
      TCP       1696    508   45458   no     208   yes  kernel      y  y  y  y  y  y  y  y  y  y  y  y  y  n  y  y  y  y  y
      
      lpq83:~# echo 131072 >/proc/sys/net/ipv4/tcp_notsent_lowat
      lpq83:~# (super_netperf 200 -t TCP_STREAM -H remote -l 90 &); sleep 60 ; grep TCP /proc/net/protocols
      TCPv6     1880      2   20567   no     208   yes  ipv6        y  y  y  y  y  y  y  y  y  y  y  y  y  n  y  y  y  y  y
      TCP       1696    508   20567   no     208   yes  kernel      y  y  y  y  y  y  y  y  y  y  y  y  y  n  y  y  y  y  y
      
      Using 128KB has no bad effect on the throughput or cpu usage
      of a single flow, although there is an increase of context switches.
      
      A bonus is that we hold socket lock for a shorter amount
      of time and should improve latencies of ACK processing.
      
      lpq83:~# echo -1 >/proc/sys/net/ipv4/tcp_notsent_lowat
      lpq83:~# perf stat -e context-switches ./netperf -H 7.7.7.84 -t omni -l 20 -c -i10,3
      OMNI Send TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 7.7.7.84 () port 0 AF_INET : +/-2.500% @ 99% conf.
      Local       Remote      Local  Elapsed Throughput Throughput  Local Local  Remote Remote Local   Remote  Service
      Send Socket Recv Socket Send   Time               Units       CPU   CPU    CPU    CPU    Service Service Demand
      Size        Size        Size   (sec)                          Util  Util   Util   Util   Demand  Demand  Units
      Final       Final                                             %     Method %      Method
      1651584     6291456     16384  20.00   17447.90   10^6bits/s  3.13  S      -1.00  U      0.353   -1.000  usec/KB
      
       Performance counter stats for './netperf -H 7.7.7.84 -t omni -l 20 -c -i10,3':
      
                 412,514 context-switches
      
           200.034645535 seconds time elapsed
      
      lpq83:~# echo 131072 >/proc/sys/net/ipv4/tcp_notsent_lowat
      lpq83:~# perf stat -e context-switches ./netperf -H 7.7.7.84 -t omni -l 20 -c -i10,3
      OMNI Send TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 7.7.7.84 () port 0 AF_INET : +/-2.500% @ 99% conf.
      Local       Remote      Local  Elapsed Throughput Throughput  Local Local  Remote Remote Local   Remote  Service
      Send Socket Recv Socket Send   Time               Units       CPU   CPU    CPU    CPU    Service Service Demand
      Size        Size        Size   (sec)                          Util  Util   Util   Util   Demand  Demand  Units
      Final       Final                                             %     Method %      Method
      1593240     6291456     16384  20.00   17321.16   10^6bits/s  3.35  S      -1.00  U      0.381   -1.000  usec/KB
      
       Performance counter stats for './netperf -H 7.7.7.84 -t omni -l 20 -c -i10,3':
      
               2,675,818 context-switches
      
           200.029651391 seconds time elapsed
      Signed-off-by: NEric Dumazet <edumazet@google.com>
      Cc: Neal Cardwell <ncardwell@google.com>
      Cc: Yuchung Cheng <ycheng@google.com>
      Acked-By: NYuchung Cheng <ycheng@google.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      c9bee3b7
  12. 20 7月, 2013 1 次提交
  13. 13 6月, 2013 1 次提交
  14. 21 3月, 2013 1 次提交
    • Y
      tcp: refactor F-RTO · 9b44190d
      Yuchung Cheng 提交于
      The patch series refactor the F-RTO feature (RFC4138/5682).
      
      This is to simplify the loss recovery processing. Existing F-RTO
      was developed during the experimental stage (RFC4138) and has
      many experimental features.  It takes a separate code path from
      the traditional timeout processing by overloading CA_Disorder
      instead of using CA_Loss state. This complicates CA_Disorder state
      handling because it's also used for handling dubious ACKs and undos.
      While the algorithm in the RFC does not change the congestion control,
      the implementation intercepts congestion control in various places
      (e.g., frto_cwnd in tcp_ack()).
      
      The new code implements newer F-RTO RFC5682 using CA_Loss processing
      path.  F-RTO becomes a small extension in the timeout processing
      and interfaces with congestion control and Eifel undo modules.
      It lets congestion control (module) determines how many to send
      independently.  F-RTO only chooses what to send in order to detect
      spurious retranmission. If timeout is found spurious it invokes
      existing Eifel undo algorithms like DSACK or TCP timestamp based
      detection.
      
      The first patch removes all F-RTO code except the sysctl_tcp_frto is
      left for the new implementation.  Since CA_EVENT_FRTO is removed, TCP
      westwood now computes ssthresh on regular timeout CA_EVENT_LOSS event.
      Signed-off-by: NYuchung Cheng <ycheng@google.com>
      Acked-by: NNeal Cardwell <ncardwell@google.com>
      Acked-by: NEric Dumazet <edumazet@google.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      9b44190d
  15. 18 3月, 2013 1 次提交
    • C
      tcp: Remove TCPCT · 1a2c6181
      Christoph Paasch 提交于
      TCPCT uses option-number 253, reserved for experimental use and should
      not be used in production environments.
      Further, TCPCT does not fully implement RFC 6013.
      
      As a nice side-effect, removing TCPCT increases TCP's performance for
      very short flows:
      
      Doing an apache-benchmark with -c 100 -n 100000, sending HTTP-requests
      for files of 1KB size.
      
      before this patch:
      	average (among 7 runs) of 20845.5 Requests/Second
      after:
      	average (among 7 runs) of 21403.6 Requests/Second
      Signed-off-by: NChristoph Paasch <christoph.paasch@uclouvain.be>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      1a2c6181
  16. 12 3月, 2013 1 次提交
    • N
      tcp: Tail loss probe (TLP) · 6ba8a3b1
      Nandita Dukkipati 提交于
      This patch series implement the Tail loss probe (TLP) algorithm described
      in http://tools.ietf.org/html/draft-dukkipati-tcpm-tcp-loss-probe-01. The
      first patch implements the basic algorithm.
      
      TLP's goal is to reduce tail latency of short transactions. It achieves
      this by converting retransmission timeouts (RTOs) occuring due
      to tail losses (losses at end of transactions) into fast recovery.
      TLP transmits one packet in two round-trips when a connection is in
      Open state and isn't receiving any ACKs. The transmitted packet, aka
      loss probe, can be either new or a retransmission. When there is tail
      loss, the ACK from a loss probe triggers FACK/early-retransmit based
      fast recovery, thus avoiding a costly RTO. In the absence of loss,
      there is no change in the connection state.
      
      PTO stands for probe timeout. It is a timer event indicating
      that an ACK is overdue and triggers a loss probe packet. The PTO value
      is set to max(2*SRTT, 10ms) and is adjusted to account for delayed
      ACK timer when there is only one oustanding packet.
      
      TLP Algorithm
      
      On transmission of new data in Open state:
        -> packets_out > 1: schedule PTO in max(2*SRTT, 10ms).
        -> packets_out == 1: schedule PTO in max(2*RTT, 1.5*RTT + 200ms)
        -> PTO = min(PTO, RTO)
      
      Conditions for scheduling PTO:
        -> Connection is in Open state.
        -> Connection is either cwnd limited or no new data to send.
        -> Number of probes per tail loss episode is limited to one.
        -> Connection is SACK enabled.
      
      When PTO fires:
        new_segment_exists:
          -> transmit new segment.
          -> packets_out++. cwnd remains same.
      
        no_new_packet:
          -> retransmit the last segment.
             Its ACK triggers FACK or early retransmit based recovery.
      
      ACK path:
        -> rearm RTO at start of ACK processing.
        -> reschedule PTO if need be.
      
      In addition, the patch includes a small variation to the Early Retransmit
      (ER) algorithm, such that ER and TLP together can in principle recover any
      N-degree of tail loss through fast recovery. TLP is controlled by the same
      sysctl as ER, tcp_early_retrans sysctl.
      tcp_early_retrans==0; disables TLP and ER.
      		 ==1; enables RFC5827 ER.
      		 ==2; delayed ER.
      		 ==3; TLP and delayed ER. [DEFAULT]
      		 ==4; TLP only.
      
      The TLP patch series have been extensively tested on Google Web servers.
      It is most effective for short Web trasactions, where it reduced RTOs by 15%
      and improved HTTP response time (average by 6%, 99th percentile by 10%).
      The transmitted probes account for <0.5% of the overall transmissions.
      Signed-off-by: NNandita Dukkipati <nanditad@google.com>
      Acked-by: NNeal Cardwell <ncardwell@google.com>
      Acked-by: NYuchung Cheng <ycheng@google.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      6ba8a3b1
  17. 06 2月, 2013 1 次提交
  18. 29 1月, 2013 1 次提交
  19. 07 1月, 2013 1 次提交
  20. 29 12月, 2012 1 次提交
  21. 19 11月, 2012 1 次提交
  22. 12 10月, 2012 1 次提交
  23. 01 9月, 2012 1 次提交
    • J
      tcp: TCP Fast Open Server - header & support functions · 10467163
      Jerry Chu 提交于
      This patch adds all the necessary data structure and support
      functions to implement TFO server side. It also documents a number
      of flags for the sysctl_tcp_fastopen knob, and adds a few Linux
      extension MIBs.
      
      In addition, it includes the following:
      
      1. a new TCP_FASTOPEN socket option an application must call to
      supply a max backlog allowed in order to enable TFO on its listener.
      
      2. A number of key data structures:
      "fastopen_rsk" in tcp_sock - for a big socket to access its
      request_sock for retransmission and ack processing purpose. It is
      non-NULL iff 3WHS not completed.
      
      "fastopenq" in request_sock_queue - points to a per Fast Open
      listener data structure "fastopen_queue" to keep track of qlen (# of
      outstanding Fast Open requests) and max_qlen, among other things.
      
      "listener" in tcp_request_sock - to point to the original listener
      for book-keeping purpose, i.e., to maintain qlen against max_qlen
      as part of defense against IP spoofing attack.
      
      3. various data structure and functions, many in tcp_fastopen.c, to
      support server side Fast Open cookie operations, including
      /proc/sys/net/ipv4/tcp_fastopen_key to allow manual rekeying.
      Signed-off-by: NH.K. Jerry Chu <hkchu@google.com>
      Cc: Yuchung Cheng <ycheng@google.com>
      Cc: Neal Cardwell <ncardwell@google.com>
      Cc: Eric Dumazet <edumazet@google.com>
      Cc: Tom Herbert <therbert@google.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      10467163
  24. 15 8月, 2012 1 次提交
    • E
      userns: Use kgids for sysctl_ping_group_range · 7064d16e
      Eric W. Biederman 提交于
      - Store sysctl_ping_group_range as a paire of kgid_t values
        instead of a pair of gid_t values.
      - Move the kgid conversion work from ping_init_sock into ipv4_ping_group_range
      - For invalid cases reset to the default disabled state.
      
      With the kgid_t conversion made part of the original value sanitation
      from userspace understand how the code will react becomes clearer
      and it becomes possible to set the sysctl ping group range from
      something other than the initial user namespace.
      
      Cc: Vasiliy Kulikov <segoon@openwall.com>
      Acked-by: NDavid S. Miller <davem@davemloft.net>
      Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>
      7064d16e
  25. 01 8月, 2012 1 次提交
    • A
      memcg: rename config variables · c255a458
      Andrew Morton 提交于
      Sanity:
      
      CONFIG_CGROUP_MEM_RES_CTLR -> CONFIG_MEMCG
      CONFIG_CGROUP_MEM_RES_CTLR_SWAP -> CONFIG_MEMCG_SWAP
      CONFIG_CGROUP_MEM_RES_CTLR_SWAP_ENABLED -> CONFIG_MEMCG_SWAP_ENABLED
      CONFIG_CGROUP_MEM_RES_CTLR_KMEM -> CONFIG_MEMCG_KMEM
      
      [mhocko@suse.cz: fix missed bits]
      Cc: Glauber Costa <glommer@parallels.com>
      Acked-by: NMichal Hocko <mhocko@suse.cz>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      c255a458
  26. 31 7月, 2012 1 次提交
  27. 20 7月, 2012 1 次提交
    • Y
      net-tcp: Fast Open base · 2100c8d2
      Yuchung Cheng 提交于
      This patch impelements the common code for both the client and server.
      
      1. TCP Fast Open option processing. Since Fast Open does not have an
         option number assigned by IANA yet, it shares the experiment option
         code 254 by implementing draft-ietf-tcpm-experimental-options
         with a 16 bits magic number 0xF989. This enables global experiments
         without clashing the scarce(2) experimental options available for TCP.
      
         When the draft status becomes standard (maybe), the client should
         switch to the new option number assigned while the server supports
         both numbers for transistion.
      
      2. The new sysctl tcp_fastopen
      
      3. A place holder init function
      Signed-off-by: NYuchung Cheng <ycheng@google.com>
      Acked-by: NEric Dumazet <edumazet@google.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      2100c8d2
  28. 17 7月, 2012 1 次提交
    • E
      tcp: implement RFC 5961 3.2 · 282f23c6
      Eric Dumazet 提交于
      Implement the RFC 5691 mitigation against Blind
      Reset attack using RST bit.
      
      Idea is to validate incoming RST sequence,
      to match RCV.NXT value, instead of previouly accepted
      window : (RCV.NXT <= SEG.SEQ < RCV.NXT+RCV.WND)
      
      If sequence is in window but not an exact match, send
      a "challenge ACK", so that the other part can resend an
      RST with the appropriate sequence.
      
      Add a new sysctl, tcp_challenge_ack_limit, to limit
      number of challenge ACK sent per second.
      
      Add a new SNMP counter to count number of challenge acks sent.
      (netstat -s | grep TCPChallengeACK)
      Signed-off-by: NEric Dumazet <edumazet@google.com>
      Cc: Kiran Kumar Kella <kkiran@broadcom.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      282f23c6
  29. 12 7月, 2012 1 次提交
    • E
      tcp: TCP Small Queues · 46d3ceab
      Eric Dumazet 提交于
      This introduce TSQ (TCP Small Queues)
      
      TSQ goal is to reduce number of TCP packets in xmit queues (qdisc &
      device queues), to reduce RTT and cwnd bias, part of the bufferbloat
      problem.
      
      sk->sk_wmem_alloc not allowed to grow above a given limit,
      allowing no more than ~128KB [1] per tcp socket in qdisc/dev layers at a
      given time.
      
      TSO packets are sized/capped to half the limit, so that we have two
      TSO packets in flight, allowing better bandwidth use.
      
      As a side effect, setting the limit to 40000 automatically reduces the
      standard gso max limit (65536) to 40000/2 : It can help to reduce
      latencies of high prio packets, having smaller TSO packets.
      
      This means we divert sock_wfree() to a tcp_wfree() handler, to
      queue/send following frames when skb_orphan() [2] is called for the
      already queued skbs.
      
      Results on my dev machines (tg3/ixgbe nics) are really impressive,
      using standard pfifo_fast, and with or without TSO/GSO.
      
      Without reduction of nominal bandwidth, we have reduction of buffering
      per bulk sender :
      < 1ms on Gbit (instead of 50ms with TSO)
      < 8ms on 100Mbit (instead of 132 ms)
      
      I no longer have 4 MBytes backlogged in qdisc by a single netperf
      session, and both side socket autotuning no longer use 4 Mbytes.
      
      As skb destructor cannot restart xmit itself ( as qdisc lock might be
      taken at this point ), we delegate the work to a tasklet. We use one
      tasklest per cpu for performance reasons.
      
      If tasklet finds a socket owned by the user, it sets TSQ_OWNED flag.
      This flag is tested in a new protocol method called from release_sock(),
      to eventually send new segments.
      
      [1] New /proc/sys/net/ipv4/tcp_limit_output_bytes tunable
      [2] skb_orphan() is usually called at TX completion time,
        but some drivers call it in their start_xmit() handler.
        These drivers should at least use BQL, or else a single TCP
        session can still fill the whole NIC TX ring, since TSQ will
        have no effect.
      Signed-off-by: NEric Dumazet <edumazet@google.com>
      Cc: Dave Taht <dave.taht@bufferbloat.net>
      Cc: Tom Herbert <therbert@google.com>
      Cc: Matt Mathis <mattmathis@google.com>
      Cc: Yuchung Cheng <ycheng@google.com>
      Cc: Nandita Dukkipati <nanditad@google.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      46d3ceab
  30. 23 6月, 2012 1 次提交
    • A
      ipv4: Add sysctl knob to control early socket demux · 6648bd7e
      Alexander Duyck 提交于
      This change is meant to add a control for disabling early socket demux.
      The main motivation behind this patch is to provide an option to disable
      the feature as it adds an additional cost to routing that reduces overall
      throughput by up to 5%.  For example one of my systems went from 12.1Mpps
      to 11.6 after the early socket demux was added.  It looks like the reason
      for the regression is that we are now having to perform two lookups, first
      the one for an established socket, and then the one for the routing table.
      
      By adding this patch and toggling the value for ip_early_demux to 0 I am
      able to get back to the 12.1Mpps I was previously seeing.
      
      [ Move local variables in ip_rcv_finish() down into the basic
        block in which they are actually used.  -DaveM ]
      Signed-off-by: NAlexander Duyck <alexander.h.duyck@intel.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      6648bd7e
  31. 03 5月, 2012 1 次提交
    • Y
      tcp: early retransmit · eed530b6
      Yuchung Cheng 提交于
      This patch implements RFC 5827 early retransmit (ER) for TCP.
      It reduces DUPACK threshold (dupthresh) if outstanding packets are
      less than 4 to recover losses by fast recovery instead of timeout.
      
      While the algorithm is simple, small but frequent network reordering
      makes this feature dangerous: the connection repeatedly enter
      false recovery and degrade performance. Therefore we implement
      a mitigation suggested in the appendix of the RFC that delays
      entering fast recovery by a small interval, i.e., RTT/4. Currently
      ER is conservative and is disabled for the rest of the connection
      after the first reordering event. A large scale web server
      experiment on the performance impact of ER is summarized in
      section 6 of the paper "Proportional Rate Reduction for TCP”,
      IMC 2011. http://conferences.sigcomm.org/imc/2011/docs/p155.pdf
      
      Note that Linux has a similar feature called THIN_DUPACK. The
      differences are THIN_DUPACK do not mitigate reorderings and is only
      used after slow start. Currently ER is disabled if THIN_DUPACK is
      enabled. I would be happy to merge THIN_DUPACK feature with ER if
      people think it's a good idea.
      
      ER is enabled by sysctl_tcp_early_retrans:
        0: Disables ER
      
        1: Reduce dupthresh to packets_out - 1 when outstanding packets < 4.
      
        2: (Default) reduce dupthresh like mode 1. In addition, delay
           entering fast recovery by RTT/4.
      
      Note: mode 2 is implemented in the third part of this patch series.
      Signed-off-by: NYuchung Cheng <ycheng@google.com>
      Acked-by: NNeal Cardwell <ncardwell@google.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      eed530b6
  32. 21 4月, 2012 3 次提交
  33. 16 4月, 2012 1 次提交
  34. 03 2月, 2012 1 次提交