- 29 9月, 2014 4 次提交
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由 Daniel Borkmann 提交于
This patch adds a flag to TCP congestion algorithms that allows for requesting to mark IPv4/IPv6 sockets with transport as ECN capable, that is, ECT(0), when required by a congestion algorithm. It is currently used and needed in DataCenter TCP (DCTCP), as it requires both peers to assert ECT on all IP packets sent - it uses ECN feedback (i.e. CE, Congestion Encountered information) from switches inside the data center to derive feedback to the end hosts. Therefore, simply add a new flag to icsk_ca_ops. Note that DCTCP's algorithm/behaviour slightly diverges from RFC3168, therefore this is only (!) enabled iff the assigned congestion control ops module has requested this. By that, we can tightly couple this logic really only to the provided congestion control ops. Joint work with Florian Westphal and Glenn Judd. Signed-off-by: NDaniel Borkmann <dborkman@redhat.com> Signed-off-by: NFlorian Westphal <fw@strlen.de> Signed-off-by: NGlenn Judd <glenn.judd@morganstanley.com> Acked-by: NStephen Hemminger <stephen@networkplumber.org> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Florian Westphal 提交于
Split assignment and initialization from one into two functions. This is required by followup patches that add Datacenter TCP (DCTCP) congestion control algorithm - we need to be able to determine if the connection is moderated by DCTCP before the 3WHS has finished. As we walk the available congestion control list during the assignment, we are always guaranteed to have Reno present as it's fixed compiled-in. Therefore, since we're doing the early assignment, we don't have a real use for the Reno alias tcp_init_congestion_ops anymore and can thus remove it. Actual usage of the congestion control operations are being made after the 3WHS has finished, in some cases however we can access get_info() via diag if implemented, therefore we need to zero out the private area for those modules. Joint work with Daniel Borkmann and Glenn Judd. Signed-off-by: NFlorian Westphal <fw@strlen.de> Signed-off-by: NDaniel Borkmann <dborkman@redhat.com> Signed-off-by: NGlenn Judd <glenn.judd@morganstanley.com> Acked-by: NStephen Hemminger <stephen@networkplumber.org> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Eric Dumazet 提交于
Our goal is to access no more than one cache line access per skb in a write or receive queue when doing the various walks. After recent TCP_SKB_CB() reorganizations, it is almost done. Last part is tcp_skb_pcount() which currently uses skb_shinfo(skb)->gso_segs, which is a terrible choice, because it needs 3 cache lines in current kernel (skb->head, skb->end, and shinfo->gso_segs are all in 3 different cache lines, far from skb->cb) This very simple patch reuses space currently taken by tcp_tw_isn only in input path, as tcp_skb_pcount is only needed for skb stored in write queue. This considerably speeds up tcp_ack(), granted we avoid shinfo->tx_flags to get SKBTX_ACK_TSTAMP, which seems possible. This also speeds up all sack processing in general. This speeds up tcp_sendmsg() because it no longer has to access/dirty shinfo. Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Eric Dumazet 提交于
TCP maintains lists of skb in write queue, and in receive queues (in order and out of order queues) Scanning these lists both in input and output path usually requires access to skb->next, TCP_SKB_CB(skb)->seq, and TCP_SKB_CB(skb)->end_seq These fields are currently in two different cache lines, meaning we waste lot of memory bandwidth when these queues are big and flows have either packet drops or packet reorders. We can move TCP_SKB_CB(skb)->header at the end of TCP_SKB_CB, because this header is not used in fast path. This allows TCP to search much faster in the skb lists. Even with regular flows, we save one cache line miss in fast path. Thanks to Christoph Paasch for noticing we need to cleanup skb->cb[] (IPCB/IP6CB) before entering IP stack in tx path, and that I forgot IPCB use in tcp_v4_hnd_req() and tcp_v4_save_options(). Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 06 9月, 2014 2 次提交
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由 Eric Dumazet 提交于
After commit 740b0f18 ("tcp: switch rtt estimations to usec resolution"), we no longer need to maintain timestamps in two different fields. TCP_SKB_CB(skb)->when can be removed, as same information sits in skb_mstamp.stamp_jiffies Signed-off-by: NEric Dumazet <edumazet@google.com> Acked-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Eric Dumazet 提交于
TCP_SKB_CB(skb)->when has different meaning in output and input paths. In output path, it contains a timestamp. In input path, it contains an ISN, chosen by tcp_timewait_state_process() Lets add a different name to ease code comprehension. Note that 'when' field will disappear in following patch, as skb_mstamp already contains timestamp, the anonymous union will promptly disappear as well. Signed-off-by: NEric Dumazet <edumazet@google.com> Acked-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 15 8月, 2014 3 次提交
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由 Hannes Frederic Sowa 提交于
tcp_tw_recycle heavily relies on tcp timestamps to build a per-host ordering of incoming connections and teardowns without the need to hold state on a specific quadruple for TCP_TIMEWAIT_LEN, but only for the last measured RTO. To do so, we keep the last seen timestamp in a per-host indexed data structure and verify if the incoming timestamp in a connection request is strictly greater than the saved one during last connection teardown. Thus we can verify later on that no old data packets will be accepted by the new connection. During moving a socket to time-wait state we already verify if timestamps where seen on a connection. Only if that was the case we let the time-wait socket expire after the RTO, otherwise normal TCP_TIMEWAIT_LEN will be used. But we don't verify this on incoming SYN packets. If a connection teardown was less than TCP_PAWS_MSL seconds in the past we cannot guarantee to not accept data packets from an old connection if no timestamps are present. We should drop this SYN packet. This patch closes this loophole. Please note, this patch does not make tcp_tw_recycle in any way more usable but only adds another safety check: Sporadic drops of SYN packets because of reordering in the network or in the socket backlog queues can happen. Users behing NAT trying to connect to a tcp_tw_recycle enabled server can get caught in blackholes and their connection requests may regullary get dropped because hosts behind an address translator don't have synchronized tcp timestamp clocks. tcp_tw_recycle cannot work if peers don't have tcp timestamps enabled. In general, use of tcp_tw_recycle is disadvised. Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Florian Westphal <fw@strlen.de> Signed-off-by: NHannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Neal Cardwell 提交于
Make sure we use the correct address-family-specific function for handling MTU reductions from within tcp_release_cb(). Previously AF_INET6 sockets were incorrectly always using the IPv6 code path when sometimes they were handling IPv4 traffic and thus had an IPv4 dst. Signed-off-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NEric Dumazet <edumazet@google.com> Diagnosed-by: NWillem de Bruijn <willemb@google.com> Fixes: 563d34d0 ("tcp: dont drop MTU reduction indications") Reviewed-by: NHannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Andrey Vagin 提交于
We don't know right timestamp for repaired skb-s. Wrong RTT estimations isn't good, because some congestion modules heavily depends on it. This patch adds the TCPCB_REPAIRED flag, which is included in TCPCB_RETRANS. Thanks to Eric for the advice how to fix this issue. This patch fixes the warning: [ 879.562947] WARNING: CPU: 0 PID: 2825 at net/ipv4/tcp_input.c:3078 tcp_ack+0x11f5/0x1380() [ 879.567253] CPU: 0 PID: 2825 Comm: socket-tcpbuf-l Not tainted 3.16.0-next-20140811 #1 [ 879.567829] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 879.568177] 0000000000000000 00000000c532680c ffff880039643d00 ffffffff817aa2d2 [ 879.568776] 0000000000000000 ffff880039643d38 ffffffff8109afbd ffff880039d6ba80 [ 879.569386] ffff88003a449800 000000002983d6bd 0000000000000000 000000002983d6bc [ 879.569982] Call Trace: [ 879.570264] [<ffffffff817aa2d2>] dump_stack+0x4d/0x66 [ 879.570599] [<ffffffff8109afbd>] warn_slowpath_common+0x7d/0xa0 [ 879.570935] [<ffffffff8109b0ea>] warn_slowpath_null+0x1a/0x20 [ 879.571292] [<ffffffff816d0a05>] tcp_ack+0x11f5/0x1380 [ 879.571614] [<ffffffff816d10bd>] tcp_rcv_established+0x1ed/0x710 [ 879.571958] [<ffffffff816dc9da>] tcp_v4_do_rcv+0x10a/0x370 [ 879.572315] [<ffffffff81657459>] release_sock+0x89/0x1d0 [ 879.572642] [<ffffffff816c81a0>] do_tcp_setsockopt.isra.36+0x120/0x860 [ 879.573000] [<ffffffff8110a52e>] ? rcu_read_lock_held+0x6e/0x80 [ 879.573352] [<ffffffff816c8912>] tcp_setsockopt+0x32/0x40 [ 879.573678] [<ffffffff81654ac4>] sock_common_setsockopt+0x14/0x20 [ 879.574031] [<ffffffff816537b0>] SyS_setsockopt+0x80/0xf0 [ 879.574393] [<ffffffff817b40a9>] system_call_fastpath+0x16/0x1b [ 879.574730] ---[ end trace a17cbc38eb8c5c00 ]--- v2: moving setting of skb->when for repaired skb-s in tcp_write_xmit, where it's set for other skb-s. Fixes: 431a9124 ("tcp: timestamp SYN+DATA messages") Fixes: 740b0f18 ("tcp: switch rtt estimations to usec resolution") Cc: Eric Dumazet <edumazet@google.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: "David S. Miller" <davem@davemloft.net> Signed-off-by: NAndrey Vagin <avagin@openvz.org> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 06 8月, 2014 1 次提交
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由 Neal Cardwell 提交于
This commit reduces spurious retransmits due to apparent SACK reneging by only reacting to SACK reneging that persists for a short delay. When a sequence space hole at snd_una is filled, some TCP receivers send a series of ACKs as they apparently scan their out-of-order queue and cumulatively ACK all the packets that have now been consecutiveyly received. This is essentially misbehavior B in "Misbehaviors in TCP SACK generation" ACM SIGCOMM Computer Communication Review, April 2011, so we suspect that this is from several common OSes (Windows 2000, Windows Server 2003, Windows XP). However, this issue has also been seen in other cases, e.g. the netdev thread "TCP being hoodwinked into spurious retransmissions by lack of timestamps?" from March 2014, where the receiver was thought to be a BSD box. Since snd_una would temporarily be adjacent to a previously SACKed range in these scenarios, this receiver behavior triggered the Linux SACK reneging code path in the sender. This led the sender to clear the SACK scoreboard, enter CA_Loss, and spuriously retransmit (potentially) every packet from the entire write queue at line rate just a few milliseconds before the ACK for each packet arrives at the sender. To avoid such situations, now when a sender sees apparent reneging it does not yet retransmit, but rather adjusts the RTO timer to give the receiver a little time (max(RTT/2, 10ms)) to send us some more ACKs that will restore sanity to the SACK scoreboard. If the reneging persists until this RTO then, as before, we clear the SACK scoreboard and enter CA_Loss. A 10ms delay tolerates a receiver sending such a stream of ACKs at 56Kbit/sec. And to allow for receivers with slower or more congested paths, we wait for at least RTT/2. We validated the resulting max(RTT/2, 10ms) delay formula with a mix of North American and South American Google web server traffic, and found that for ACKs displaying transient reneging: (1) 90% of inter-ACK delays were less than 10ms (2) 99% of inter-ACK delays were less than RTT/2 In tests on Google web servers this commit reduced reneging events by 75%-90% (as measured by the TcpExtTCPSACKReneging counter), without any measurable impact on latency for user HTTP and SPDY requests. Signed-off-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 16 7月, 2014 1 次提交
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由 Christoph Paasch 提交于
Since Yuchung's 9b44190d (tcp: refactor F-RTO), tcp_enter_cwr is always called with set_ssthresh = 1. Thus, we can remove this argument from tcp_enter_cwr. Further, as we remove this one, tcp_init_cwnd_reduction is then always called with set_ssthresh = true, and so we can get rid of this argument as well. Cc: Yuchung Cheng <ycheng@google.com> Signed-off-by: NChristoph Paasch <christoph.paasch@uclouvain.be> Acked-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 08 7月, 2014 1 次提交
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由 Neal Cardwell 提交于
Always store in snt_synack the time at which the server received the first client SYN and attempted to send the first SYNACK. Recent commit aa27fc50 ("tcp: tcp_v[46]_conn_request: fix snt_synack initialization") resolved an inconsistency between IPv4 and IPv6 in the initialization of snt_synack. This commit brings back the idea from 843f4a55 (tcp: use tcp_v4_send_synack on first SYN-ACK), which was going for the original behavior of snt_synack from the commit where it was added in 9ad7c049 ("tcp: RFC2988bis + taking RTT sample from 3WHS for the passive open side") in v3.1. In addition to being simpler (and probably a tiny bit faster), unconditionally storing the time of the first SYNACK attempt has been useful because it allows calculating a performance metric quantifying how long it took to establish a passive TCP connection. Signed-off-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NYuchung Cheng <ycheng@google.com> Cc: Octavian Purdila <octavian.purdila@intel.com> Cc: Jerry Chu <hkchu@google.com> Acked-by: NOctavian Purdila <octavian.purdila@intel.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 28 6月, 2014 10 次提交
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由 Octavian Purdila 提交于
Create tcp_conn_request and remove most of the code from tcp_v4_conn_request and tcp_v6_conn_request. Signed-off-by: NOctavian Purdila <octavian.purdila@intel.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Octavian Purdila 提交于
Add queue_add_hash member to tcp_request_sock_ops so that we can later unify tcp_v4_conn_request and tcp_v6_conn_request. Signed-off-by: NOctavian Purdila <octavian.purdila@intel.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Octavian Purdila 提交于
Add mss_clamp member to tcp_request_sock_ops so that we can later unify tcp_v4_conn_request and tcp_v6_conn_request. Signed-off-by: NOctavian Purdila <octavian.purdila@intel.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Octavian Purdila 提交于
Signed-off-by: NOctavian Purdila <octavian.purdila@intel.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Octavian Purdila 提交于
Create a new tcp_request_sock_ops method to unify the IPv4/IPv6 signature for tcp_v[46]_send_synack. This allows us to later unify tcp_v4_rtx_synack with tcp_v6_rtx_synack and tcp_v4_conn_request with tcp_v4_conn_request. Signed-off-by: NOctavian Purdila <octavian.purdila@intel.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Octavian Purdila 提交于
More work in preparation of unifying tcp_v4_conn_request and tcp_v6_conn_request: indirect the init sequence calls via the tcp_request_sock_ops. Signed-off-by: NOctavian Purdila <octavian.purdila@intel.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Octavian Purdila 提交于
Create wrappers with same signature for the IPv4/IPv6 request routing calls and use these wrappers (via route_req method from tcp_request_sock_ops) in tcp_v4_conn_request and tcp_v6_conn_request with the purpose of unifying the two functions in a later patch. We can later drop the wrapper functions and modify inet_csk_route_req and inet6_cks_route_req to use the same signature. Signed-off-by: NOctavian Purdila <octavian.purdila@intel.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Octavian Purdila 提交于
Move the specific IPv4/IPv6 cookie sequence initialization to a new method in tcp_request_sock_ops in preparation for unifying tcp_v4_conn_request and tcp_v6_conn_request. Signed-off-by: NOctavian Purdila <octavian.purdila@intel.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Octavian Purdila 提交于
Move the specific IPv4/IPv6 intializations to a new method in tcp_request_sock_ops in preparation for unifying tcp_v4_conn_request and tcp_v6_conn_request. Signed-off-by: NOctavian Purdila <octavian.purdila@intel.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Octavian Purdila 提交于
Signed-off-by: NOctavian Purdila <octavian.purdila@intel.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 18 6月, 2014 1 次提交
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由 Octavian Purdila 提交于
ir_mark initialization is done for both TCP v4 and v6, move it in the common tcp_openreq_init function. Signed-off-by: NOctavian Purdila <octavian.purdila@intel.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 11 6月, 2014 1 次提交
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由 Octavian Purdila 提交于
tcp_fragment can be called from process context (from tso_fragment). Add a new gfp parameter to allow it to preserve atomic memory if possible. Signed-off-by: NOctavian Purdila <octavian.purdila@intel.com> Reviewed-by: NChristoph Paasch <christoph.paasch@uclouvain.be> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 23 5月, 2014 1 次提交
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由 Neal Cardwell 提交于
Experience with the recent e114a710 ("tcp: fix cwnd limited checking to improve congestion control") has shown that there are common cases where that commit can cause cwnd to be much larger than necessary. This leads to TSO autosizing cooking skbs that are too large, among other things. The main problems seemed to be: (1) That commit attempted to predict the future behavior of the connection by looking at the write queue (if TSO or TSQ limit sending). That prediction sometimes overestimated future outstanding packets. (2) That commit always allowed cwnd to grow to twice the number of outstanding packets (even in congestion avoidance, where this is not needed). This commit improves both of these, by: (1) Switching to a measurement-based approach where we explicitly track the largest number of packets in flight during the past window ("max_packets_out"), and remember whether we were cwnd-limited at the moment we finished sending that flight. (2) Only allowing cwnd to grow to twice the number of outstanding packets ("max_packets_out") in slow start. In congestion avoidance mode we now only allow cwnd to grow if it was fully utilized. 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>
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- 14 5月, 2014 3 次提交
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由 Yuchung Cheng 提交于
To avoid large code duplication in IPv6, we need to first simplify the complicate SYN-ACK sending code in tcp_v4_conn_request(). To use tcp_v4(6)_send_synack() to send all SYN-ACKs, we need to initialize the mini socket's receive window before trying to create the child socket and/or building the SYN-ACK packet. So we move that initialization from tcp_make_synack() to tcp_v4_conn_request() as a new function tcp_openreq_init_req_rwin(). After this refactoring the SYN-ACK sending code is simpler and easier to implement Fast Open for IPv6. Signed-off-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NDaniel Lee <longinus00@gmail.com> Signed-off-by: NJerry Chu <hkchu@google.com> Acked-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Yuchung Cheng 提交于
Consolidate various cookie checking and generation code to simplify the fast open processing. The main goal is to reduce code duplication in tcp_v4_conn_request() for IPv6 support. Removes two experimental sysctl flags TFO_SERVER_ALWAYS and TFO_SERVER_COOKIE_NOT_CHKD used primarily for developmental debugging purposes. Signed-off-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NDaniel Lee <longinus00@gmail.com> Signed-off-by: NJerry Chu <hkchu@google.com> Signed-off-by: NEric Dumazet <edumazet@google.com> Acked-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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由 Yuchung Cheng 提交于
Move common TFO functions that will be used by both v4 and v6 to tcp_fastopen.c. Create a helper tcp_fastopen_queue_check(). Signed-off-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NDaniel Lee <longinus00@gmail.com> Signed-off-by: NJerry Chu <hkchu@google.com> Signed-off-by: NEric Dumazet <edumazet@google.com> Acked-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 04 5月, 2014 1 次提交
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由 Eric Dumazet 提交于
Commit e114a710 ("tcp: fix cwnd limited checking to improve congestion control") obsoleted in_flight parameter from tcp_is_cwnd_limited() and its callers. This patch does the removal as promised. Signed-off-by: NEric Dumazet <edumazet@google.com> Acked-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 03 5月, 2014 1 次提交
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由 Eric Dumazet 提交于
Yuchung discovered tcp_is_cwnd_limited() was returning false in slow start phase even if the application filled the socket write queue. All congestion modules take into account tcp_is_cwnd_limited() before increasing cwnd, so this behavior limits slow start from probing the bandwidth at full speed. The problem is that even if write queue is full (aka we are _not_ application limited), cwnd can be under utilized if TSO should auto defer or TCP Small queues decided to hold packets. So the in_flight can be kept to smaller value, and we can get to the point tcp_is_cwnd_limited() returns false. With TCP Small Queues and FQ/pacing, this issue is more visible. We fix this by having tcp_cwnd_validate(), which is supposed to track such things, take into account unsent_segs, the number of segs that we are not sending at the moment due to TSO or TSQ, but intend to send real soon. Then when we are cwnd-limited, remember this fact while we are processing the window of ACKs that comes back. For example, suppose we have a brand new connection with cwnd=10; we are in slow start, and we send a flight of 9 packets. By the time we have received ACKs for all 9 packets we want our cwnd to be 18. We implement this by setting tp->lsnd_pending to 9, and considering ourselves to be cwnd-limited while cwnd is less than twice tp->lsnd_pending (2*9 -> 18). This makes tcp_is_cwnd_limited() more understandable, by removing the GSO/TSO kludge, that tried to work around the issue. Note the in_flight parameter can be removed in a followup cleanup patch. Signed-off-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 21 4月, 2014 1 次提交
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由 Weiping Pan 提交于
Make tcp_cwnd_application_limited() static and move it from tcp_input.c to tcp_output.c Signed-off-by: NWeiping Pan <wpan@redhat.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 21 3月, 2014 1 次提交
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由 Eric Dumazet 提交于
While it is true that getnstimeofday() uses about 40 cycles if TSC is available, it can use 1600 cycles if hpet is the clocksource. Switch to get_jiffies_64(), as this is more than enough, and go back to 60 seconds periods. Fixes: 8c27bd75 ("tcp: syncookies: reduce cookie lifetime to 128 seconds") Signed-off-by: NEric Dumazet <edumazet@google.com> Cc: Florian Westphal <fw@strlen.de> Acked-by: NFlorian Westphal <fw@strlen.de> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 27 2月, 2014 1 次提交
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由 Eric Dumazet 提交于
Upcoming congestion controls for TCP require usec resolution for RTT estimations. Millisecond resolution is simply not enough these days. FQ/pacing in DC environments also require this change for finer control and removal of bimodal behavior due to the current hack in tcp_update_pacing_rate() for 'small rtt' TCP_CONG_RTT_STAMP is no longer needed. As Julian Anastasov pointed out, we need to keep user compatibility : tcp_metrics used to export RTT and RTTVAR in msec resolution, so we added RTT_US and RTTVAR_US. An iproute2 patch is needed to use the new attributes if provided by the kernel. In this example ss command displays a srtt of 32 usecs (10Gbit link) lpk51:~# ./ss -i dst lpk52 Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port tcp ESTAB 0 1 10.246.11.51:42959 10.246.11.52:64614 cubic wscale:6,6 rto:201 rtt:0.032/0.001 ato:40 mss:1448 cwnd:10 send 3620.0Mbps pacing_rate 7240.0Mbps unacked:1 rcv_rtt:993 rcv_space:29559 Updated iproute2 ip command displays : lpk51:~# ./ip tcp_metrics | grep 10.246.11.52 10.246.11.52 age 561.914sec cwnd 10 rtt 274us rttvar 213us source 10.246.11.51 Old binary displays : lpk51:~# ip tcp_metrics | grep 10.246.11.52 10.246.11.52 age 561.914sec cwnd 10 rtt 250us rttvar 125us source 10.246.11.51 With help from Julian Anastasov, Stephen Hemminger and Yuchung Cheng Signed-off-by: NEric Dumazet <edumazet@google.com> Acked-by: NNeal Cardwell <ncardwell@google.com> Cc: Stephen Hemminger <stephen@networkplumber.org> Cc: Yuchung Cheng <ycheng@google.com> Cc: Larry Brakmo <brakmo@google.com> Cc: Julian Anastasov <ja@ssi.bg> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 22 2月, 2014 1 次提交
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由 Eric Dumazet 提交于
This patch fixes two bugs in fastopen : 1) The tcp_sendmsg(..., @size) argument was ignored. Code was relying on user not fooling the kernel with iovec mismatches 2) When MTU is about 64KB, tcp_send_syn_data() attempts order-5 allocations, which are likely to fail when memory gets fragmented. Fixes: 783237e8 ("net-tcp: Fast Open client - sending SYN-data") Signed-off-by: NEric Dumazet <edumazet@google.com> Cc: Yuchung Cheng <ycheng@google.com> Acked-by: NYuchung Cheng <ycheng@google.com> Tested-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 14 2月, 2014 1 次提交
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由 Stanislav Fomichev 提交于
Commit 684bad11 "tcp: use PRR to reduce cwin in CWR state" removed all calls to min_cwnd, so we can safely remove it. Also, remove tcp_reno_min_cwnd because it was only used for min_cwnd. Signed-off-by: NStanislav Fomichev <stfomichev@yandex-team.ru> Acked-by: NYuchung Cheng <ycheng@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 30 12月, 2013 1 次提交
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由 stephen hemminger 提交于
The following are only used in one file: tcp_connect_init tcp_set_rto Signed-off-by: NStephen Hemminger <stephen@networkplumber.org> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 18 12月, 2013 1 次提交
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由 Eric Dumazet 提交于
While investigating performance problems on small RPC workloads, I noticed linux TCP stack was always splitting the last TSO skb into two parts (skbs). One being a multiple of MSS, and a small one with the Push flag. This split is done even if TCP_NODELAY is set, or if no small packet is in flight. Example with request/response of 4K/4K IP A > B: . ack 68432 win 2783 <nop,nop,timestamp 6524593 6525001> IP A > B: . 65537:68433(2896) ack 69632 win 2783 <nop,nop,timestamp 6524593 6525001> IP A > B: P 68433:69633(1200) ack 69632 win 2783 <nop,nop,timestamp 6524593 6525001> IP B > A: . ack 68433 win 2768 <nop,nop,timestamp 6525001 6524593> IP B > A: . 69632:72528(2896) ack 69633 win 2768 <nop,nop,timestamp 6525001 6524593> IP B > A: P 72528:73728(1200) ack 69633 win 2768 <nop,nop,timestamp 6525001 6524593> IP A > B: . ack 72528 win 2783 <nop,nop,timestamp 6524593 6525001> IP A > B: . 69633:72529(2896) ack 73728 win 2783 <nop,nop,timestamp 6524593 6525001> IP A > B: P 72529:73729(1200) ack 73728 win 2783 <nop,nop,timestamp 6524593 6525001> We can avoid this split by including the Nagle tests at the right place. Note : If some NIC had trouble sending TSO packets with a partial last segment, we would have hit the problem in GRO/forwarding workload already. tcp_minshall_update() is moved to tcp_output.c and is updated as we might feed a TSO packet with a partial last segment. This patch tremendously improves performance, as the traffic now looks like : IP A > B: . ack 98304 win 2783 <nop,nop,timestamp 6834277 6834685> IP A > B: P 94209:98305(4096) ack 98304 win 2783 <nop,nop,timestamp 6834277 6834685> IP B > A: . ack 98305 win 2768 <nop,nop,timestamp 6834686 6834277> IP B > A: P 98304:102400(4096) ack 98305 win 2768 <nop,nop,timestamp 6834686 6834277> IP A > B: . ack 102400 win 2783 <nop,nop,timestamp 6834279 6834686> IP A > B: P 98305:102401(4096) ack 102400 win 2783 <nop,nop,timestamp 6834279 6834686> IP B > A: . ack 102401 win 2768 <nop,nop,timestamp 6834687 6834279> IP B > A: P 102400:106496(4096) ack 102401 win 2768 <nop,nop,timestamp 6834687 6834279> IP A > B: . ack 106496 win 2783 <nop,nop,timestamp 6834280 6834687> IP A > B: P 102401:106497(4096) ack 106496 win 2783 <nop,nop,timestamp 6834280 6834687> IP B > A: . ack 106497 win 2768 <nop,nop,timestamp 6834688 6834280> IP B > A: P 106496:110592(4096) ack 106497 win 2768 <nop,nop,timestamp 6834688 6834280> Before : lpq83:~# nstat >/dev/null;perf stat ./super_netperf 200 -t TCP_RR -H lpq84 -l 20 -- -r 4K,4K 280774 Performance counter stats for './super_netperf 200 -t TCP_RR -H lpq84 -l 20 -- -r 4K,4K': 205719.049006 task-clock # 9.278 CPUs utilized 8,449,968 context-switches # 0.041 M/sec 1,935,997 CPU-migrations # 0.009 M/sec 160,541 page-faults # 0.780 K/sec 548,478,722,290 cycles # 2.666 GHz [83.20%] 455,240,670,857 stalled-cycles-frontend # 83.00% frontend cycles idle [83.48%] 272,881,454,275 stalled-cycles-backend # 49.75% backend cycles idle [66.73%] 166,091,460,030 instructions # 0.30 insns per cycle # 2.74 stalled cycles per insn [83.39%] 29,150,229,399 branches # 141.699 M/sec [83.30%] 1,943,814,026 branch-misses # 6.67% of all branches [83.32%] 22.173517844 seconds time elapsed lpq83:~# nstat | egrep "IpOutRequests|IpExtOutOctets" IpOutRequests 16851063 0.0 IpExtOutOctets 23878580777 0.0 After patch : lpq83:~# nstat >/dev/null;perf stat ./super_netperf 200 -t TCP_RR -H lpq84 -l 20 -- -r 4K,4K 280877 Performance counter stats for './super_netperf 200 -t TCP_RR -H lpq84 -l 20 -- -r 4K,4K': 107496.071918 task-clock # 4.847 CPUs utilized 5,635,458 context-switches # 0.052 M/sec 1,374,707 CPU-migrations # 0.013 M/sec 160,920 page-faults # 0.001 M/sec 281,500,010,924 cycles # 2.619 GHz [83.28%] 228,865,069,307 stalled-cycles-frontend # 81.30% frontend cycles idle [83.38%] 142,462,742,658 stalled-cycles-backend # 50.61% backend cycles idle [66.81%] 95,227,712,566 instructions # 0.34 insns per cycle # 2.40 stalled cycles per insn [83.43%] 16,209,868,171 branches # 150.795 M/sec [83.20%] 874,252,952 branch-misses # 5.39% of all branches [83.37%] 22.175821286 seconds time elapsed lpq83:~# nstat | egrep "IpOutRequests|IpExtOutOctets" IpOutRequests 11239428 0.0 IpExtOutOctets 23595191035 0.0 Indeed, the occupancy of tx skbs (IpExtOutOctets/IpOutRequests) is higher : 2099 instead of 1417, thus helping GRO to be more efficient when using FQ packet scheduler. Many thanks to Neal for review and ideas. Signed-off-by: NEric Dumazet <edumazet@google.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: Neal Cardwell <ncardwell@google.com> Cc: Nandita Dukkipati <nanditad@google.com> Cc: Van Jacobson <vanj@google.com> Acked-by: NNeal Cardwell <ncardwell@google.com> Tested-by: NNeal Cardwell <ncardwell@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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- 07 12月, 2013 1 次提交
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由 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>
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- 05 11月, 2013 1 次提交
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由 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>
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- 22 10月, 2013 1 次提交
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由 Eric W. Biederman 提交于
The code that is implemented is per memory cgroup not per netns, and having per netns bits is just confusing. Remove the per netns bits to make it easier to see what is really going on. Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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