| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Thu, 29 Aug 2013 13:26:17 -0700 From: Eric Dumazet <eric.dumazet@...il.com> To: David Miller <davem@...emloft.net> Cc: netdev@...r.kernel.org, ncardwell@...gle.com, ycheng@...gle.com, vanj@...gle.com, therbert@...gle.com Subject: Re: [PATCH v3 net-next] tcp: TSO packets automatic sizing On Thu, 2013-08-29 at 15:51 -0400, David Miller wrote: > Applied, please post a new copy of your accompanying packet scheduler. > > Thanks. Thanks David. I am a bit puzzled by the caching of srtt in tcp metrics. We ten to cache bufferbloated values that are almost useless. On this 50ms RTT link, the syn/synack rtt was correctly sampled at 51 jiffies, but tcp_init_metrics() finds a very high srtt cached from previous tcp flow, which ended its life with a huge cwin=327/srtt=1468 because of bufferbloat. Since the new connexion starts with IW10, the estimated rate is slightly wrong for the first ~10 incoming acks, before ewma converges to the right value... [ 4544.656476] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 51 sack_rtt 4294967295 [ 4544.656482] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 51 srtt 0 [ 4544.656496] TCP: sk ffff88085825d180 cwnd 10 packets 0 rate 231680000/srtt 408 [ 4544.707045] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 50 sack_rtt 4294967295 [ 4544.707051] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 50 srtt 1468 [ 4544.707055] TCP: sk ffff88085825d180 cwnd 11 packets 9 rate 254848000/srtt 1335 [ 4544.707067] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 50 sack_rtt 4294967295 [ 4544.707069] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 50 srtt 1335 [ 4544.707071] TCP: sk ffff88085825d180 cwnd 12 packets 10 rate 278016000/srtt 1219 [ 4544.707694] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 51 sack_rtt 4294967295 [ 4544.707699] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 51 srtt 1219 [ 4544.707703] TCP: sk ffff88085825d180 cwnd 13 packets 11 rate 301184000/srtt 1118 [ 4544.708324] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 52 sack_rtt 4294967295 [ 4544.708330] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 52 srtt 1118 [ 4544.708333] TCP: sk ffff88085825d180 cwnd 14 packets 12 rate 324352000/srtt 1031 [ 4544.708846] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 52 sack_rtt 4294967295 [ 4544.708851] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 52 srtt 1031 [ 4544.708855] TCP: sk ffff88085825d180 cwnd 15 packets 13 rate 347520000/srtt 955 [ 4544.709521] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 53 sack_rtt 4294967295 [ 4544.709526] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 53 srtt 955 [ 4544.709530] TCP: sk ffff88085825d180 cwnd 16 packets 14 rate 370688000/srtt 889 [ 4544.710103] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 53 sack_rtt 4294967295 [ 4544.710108] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 53 srtt 889 [ 4544.710111] TCP: sk ffff88085825d180 cwnd 17 packets 15 rate 393856000/srtt 831 [ 4544.710683] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 54 sack_rtt 4294967295 [ 4544.710688] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 54 srtt 831 [ 4544.710691] TCP: sk ffff88085825d180 cwnd 18 packets 16 rate 417024000/srtt 782 [ 4544.711210] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 55 sack_rtt 4294967295 [ 4544.711215] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 55 srtt 782 [ 4544.711219] TCP: sk ffff88085825d180 cwnd 19 packets 17 rate 440192000/srtt 740 [ 4544.711868] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 55 sack_rtt 4294967295 [ 4544.711873] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 55 srtt 740 [ 4544.711876] TCP: sk ffff88085825d180 cwnd 20 packets 18 rate 463360000/srtt 703 [ 4544.757576] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 51 sack_rtt 4294967295 [ 4544.757581] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 51 srtt 703 [ 4544.757585] TCP: sk ffff88085825d180 cwnd 21 packets 19 rate 486528000/srtt 667 [ 4544.757595] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 51 sack_rtt 4294967295 [ 4544.757597] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 51 srtt 667 [ 4544.757610] TCP: sk ffff88085825d180 cwnd 22 packets 20 rate 509696000/srtt 635 [ 4544.773527] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 67 sack_rtt 4294967295 [ 4544.773533] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 67 srtt 635 [ 4544.773536] TCP: sk ffff88085825d180 cwnd 23 packets 21 rate 532864000/srtt 623 [ 4544.773548] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 67 sack_rtt 4294967295 [ 4544.773560] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 67 srtt 623 [ 4544.773562] TCP: sk ffff88085825d180 cwnd 24 packets 22 rate 556032000/srtt 613 [ 4544.778208] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 71 sack_rtt 4294967295 [ 4544.778213] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 71 srtt 613 [ 4544.778216] TCP: sk ffff88085825d180 cwnd 25 packets 23 rate 579200000/srtt 608 [ 4544.778237] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 71 sack_rtt 4294967295 [ 4544.778238] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 71 srtt 608 [ 4544.778240] TCP: sk ffff88085825d180 cwnd 26 packets 24 rate 602368000/srtt 603 [ 4544.782776] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 74 sack_rtt 4294967295 [ 4544.782781] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 74 srtt 603 [ 4544.782785] TCP: sk ffff88085825d180 cwnd 27 packets 25 rate 625536000/srtt 602 [ 4544.782795] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 74 sack_rtt 4294967295 [ 4544.782808] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 74 srtt 602 ... Typical bufferbloat at the end of transfert : [ 4547.051521] TCP: sk ffff88085825d180 cwnd 327 packets 3 rate 7575936000/srtt 1581 [ 4547.052722] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 198 sack_rtt 4294967295 [ 4547.052726] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 198 srtt 1581 [ 4547.052729] TCP: sk ffff88085825d180 cwnd 327 packets 1 rate 7575936000/srtt 1582 [ 4547.053315] TCP: tcp_ack_update_rtt sk ffff88085825d180 seq_rtt 198 sack_rtt 4294967295 [ 4547.053318] TCP: tcp_rtt_estimator sk ffff88085825d180 mrtt 198 srtt 1582 [ 4547.053321] TCP: sk ffff88085825d180 cwnd 327 packets 0 rate 7575936000/srtt 1583 Maybe we could instead store a value corrected by the sk_pacing_rate rate = (big_cwin * mss) / big_srtt stored_rtt = rate / (big_cwin * mss) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists