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Date: Fri, 13 Oct 2017 15:56:16 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Traiano Welcome' <traiano@...il.com>,
"linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: Kernel Performance Tuning for High Volume SCTP traffic
From: Traiano Welcome
(copied to netdev)
> Sent: 13 October 2017 07:16
> To: linux-sctp@...r.kernel.org
> Subject: Kernel Performance Tuning for High Volume SCTP traffic
>
> Hi List
>
> I'm running a linux server processing high volumes of SCTP traffic and
> am seeing large numbers of packet overruns (ifconfig output).
I'd guess that overruns indicate that the ethernet MAC is failing to
copy the receive frames into kernel memory.
It is probably running out of receive buffers, but might be
suffering from a lack of bus bandwidth.
MAC drivers usually discard receive frames if they can't get
a replacement buffer - so you shouldn't run out of rx buffers.
This means the errors are probably below SCTP - so changing SCTP parameters
is unlikely to help.
I'd make sure any receive interrupt coalescing/mitigation is turned off.
David
> I think a large amount of performance tuning can probably be done to
> improve the linux kernel's SCTP handling performance, but there seem
> to be no guides on this available. Could anyone advise on this?
>
>
> Here are my current settings, and below, some stats:
>
>
> -----
> net.sctp.addip_enable = 0
> net.sctp.addip_noauth_enable = 0
> net.sctp.addr_scope_policy = 1
> net.sctp.association_max_retrans = 10
> net.sctp.auth_enable = 0
> net.sctp.cookie_hmac_alg = sha1
> net.sctp.cookie_preserve_enable = 1
> net.sctp.default_auto_asconf = 0
> net.sctp.hb_interval = 30000
> net.sctp.max_autoclose = 8589934
> net.sctp.max_burst = 40
> net.sctp.max_init_retransmits = 8
> net.sctp.path_max_retrans = 5
> net.sctp.pf_enable = 1
> net.sctp.pf_retrans = 0
> net.sctp.prsctp_enable = 1
> net.sctp.rcvbuf_policy = 0
> net.sctp.rto_alpha_exp_divisor = 3
> net.sctp.rto_beta_exp_divisor = 2
> net.sctp.rto_initial = 3000
> net.sctp.rto_max = 60000
> net.sctp.rto_min = 1000
> net.sctp.rwnd_update_shift = 4
> net.sctp.sack_timeout = 50
> net.sctp.sctp_mem = 61733040 82310730 123466080
> net.sctp.sctp_rmem = 40960 8655000 41943040
> net.sctp.sctp_wmem = 40960 8655000 41943040
> net.sctp.sndbuf_policy = 0
> net.sctp.valid_cookie_life = 60000
> -----
>
>
> I'm seeing a high rate of packet errors (almost all overruns) on both
> 10gb NICs attached to my linux server.
>
> The system is handling high volumes of network traffic, so this is
> likely a linux kernel tuning problem.
>
> All the normal tuning parameters I've tried thus far seems to be
> having little effect and I'm still seeing high volumes of packet
> overruns.
>
> Any pointers on other things I could try to get the system handling
> SCTP packets efficiently would be much appreciated!
>
> -----
> :~# ifconfig ens4f1
>
> ens4f1 Link encap:Ethernet HWaddr 5c:b9:01:de:0d:4c
> UP BROADCAST RUNNING PROMISC MULTICAST MTU:9000 Metric:1
> RX packets:22313514162 errors:17598241316 dropped:68
> overruns:17598241316 frame:0
> TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
> collisions:0 txqueuelen:1000
> RX bytes:31767480894219 (31.7 TB) TX bytes:0 (0.0 B)
> Interrupt:17 Memory:c9800000-c9ffffff
> -----
>
> System details:
>
> OS : Ubuntu Linux (4.11.0-14-generic #20~16.04.1-Ubuntu SMP x86_64 )
> CPU Cores : 72
> NIC Model : NetXtreme II BCM57810 10 Gigabit Ethernet
> RAM : 240 GiB
>
> NIC sample stats showing packet error rate:
>
> ----
>
> for i in `seq 1 10`;do echo "$i) `date`" - $(ifconfig ens4f0| egrep
> "RX"| egrep overruns;sleep 5);done
>
> 1) Thu Oct 12 19:50:40 SGT 2017 - RX packets:8364065830
> errors:2594507718 dropped:215 overruns:2594507718 frame:0
> 2) Thu Oct 12 19:50:45 SGT 2017 - RX packets:8365336060
> errors:2596662672 dropped:215 overruns:2596662672 frame:0
> 3) Thu Oct 12 19:50:50 SGT 2017 - RX packets:8366602087
> errors:2598840959 dropped:215 overruns:2598840959 frame:0
> 4) Thu Oct 12 19:50:55 SGT 2017 - RX packets:8367881271
> errors:2600989229 dropped:215 overruns:2600989229 frame:0
> 5) Thu Oct 12 19:51:01 SGT 2017 - RX packets:8369147536
> errors:2603157030 dropped:215 overruns:2603157030frame:0
> 6) Thu Oct 12 19:51:06 SGT 2017 - RX packets:8370149567
> errors:2604904183 dropped:215 overruns:2604904183frame:0
> 7) Thu Oct 12 19:51:11 SGT 2017 - RX packets:8371298018
> errors:2607183939 dropped:215 overruns:2607183939frame:0
> 8) Thu Oct 12 19:51:16 SGT 2017 - RX packets:8372455587
> errors:2609411186 dropped:215 overruns:2609411186frame:0
> 9) Thu Oct 12 19:51:21 SGT 2017 - RX packets:8373585102
> errors:2611680597 dropped:215 overruns:2611680597 frame:0
> 10) Thu Oct 12 19:51:26 SGT 2017 - RX packets:8374678508
> errors:2614053000 dropped:215 overruns:2614053000 frame:0
>
> ----
>
> However, checking (with tc) shows no ring buffer overruns on NIC:
>
> ----
>
> tc -s qdisc show dev ens4f0|egrep drop
>
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
>
> -----
>
> Checking tcp retransmits, the rate is low:
>
> -----
>
> for i in `seq 1 10`;do echo "`date`" - $(netstat -s | grep -i
> retransmited;sleep 2);done
>
> Thu Oct 12 20:04:29 SGT 2017 - 10633 segments retransmited
> Thu Oct 12 20:04:31 SGT 2017 - 10634 segments retransmited
> Thu Oct 12 20:04:33 SGT 2017 - 10636 segments retransmited
> Thu Oct 12 20:04:35 SGT 2017 - 10636 segments retransmited
> Thu Oct 12 20:04:37 SGT 2017 - 10638 segments retransmited
> Thu Oct 12 20:04:39 SGT 2017 - 10639 segments retransmited
> Thu Oct 12 20:04:41 SGT 2017 - 10640 segments retransmited
> Thu Oct 12 20:04:43 SGT 2017 - 10640 segments retransmited
> Thu Oct 12 20:04:45 SGT 2017 - 10643 segments retransmited
>
> ------
>
> What I've tried so far:
>
> - Tuning the NIC parameters (packet coalesce, offloading, upping NIC
> ring buffers etc ...):
>
> ethtool -L ens4f0 combined 30
> ethtool -K ens4f0 gso on rx on tx on sg on tso on
> ethtool -C ens4f0 rx-usecs 96
> ethtool -C ens4f0 adaptive-rx on
> ethtool -G ens4f0 rx 4078 tx 4078
>
> - sysctl tunables for the kernel (mainly increasing kernel tcp buffers):
>
> ---
>
> sysctl -w net.ipv4.tcp_low_latency=1
> sysctl -w net.ipv4.tcp_max_syn_backlog=16384
> sysctl -w net.core.optmem_max=20480000
> sysctl -w net.core.netdev_max_backlog=5000000
> sysctl -w net.ipv4.tcp_rmem="65536 1747600 83886080"
> sysctl -w net.core.somaxconn=1280
> sysctl -w kernel.sched_min_granularity_ns=10000000
> sysctl -w kernel.sched_wakeup_granularity_ns=15000000
> sysctl -w net.ipv4.tcp_wmem="65536 1747600 83886080"
> sysctl -w net.core.wmem_max=2147483647
> sysctl -w net.core.wmem_default=2147483647
> sysctl -w net.core.rmem_max=2147483647
> sysctl -w net.core.rmem_default=2147483647
> sysctl -w net.ipv4.tcp_congestion_control=cubic
> sysctl -w net.ipv4.tcp_rmem="163840 3495200 268754560"
> sysctl -w net.ipv4.tcp_wmem="163840 3495200 268754560"
> sysctl -w net.ipv4.udp_rmem_min="163840 3495200 268754560"
> sysctl -w net.ipv4.udp_wmem_min="163840 3495200 268754560"
> sysctl -w net.ipv4.tcp_mem="268754560 268754560 268754560"
> sysctl -w net.ipv4.udp_mem="268754560 268754560 268754560"
> sysctl -w net.ipv4.tcp_mtu_probing=1
> sysctl -w net.ipv4.tcp_slow_start_after_idle=0
>
>
> Results after this (apparently not much):
>
>
> ----
>
> :~# for i in `seq 1 10`;do echo "$i) `date`" - $(ifconfig ens4f1|
> egrep "RX"| egrep overruns;sleep 5);done
>
> 1) Thu Oct 12 20:42:56 SGT 2017 - RX packets:16260617113
> errors:10964865836 dropped:68 overruns:10964865836 frame:0
> 2) Thu Oct 12 20:43:01 SGT 2017 - RX packets:16263268608
> errors:10969589847 dropped:68 overruns:10969589847 frame:0
> 3) Thu Oct 12 20:43:06 SGT 2017 - RX packets:16265869693
> errors:10974489639 dropped:68 overruns:10974489639 frame:0
> 4) Thu Oct 12 20:43:11 SGT 2017 - RX packets:16268487078
> errors:10979323070 dropped:68 overruns:10979323070 frame:0
> 5) Thu Oct 12 20:43:16 SGT 2017 - RX packets:16271098501
> errors:10984193349 dropped:68 overruns:10984193349 frame:0
> 6) Thu Oct 12 20:43:21 SGT 2017 - RX packets:16273804004
> errors:10988857622 dropped:68 overruns:10988857622 frame:0
> 7) Thu Oct 12 20:43:26 SGT 2017 - RX packets:16276493470
> errors:10993340211 dropped:68 overruns:10993340211 frame:0
> 8) Thu Oct 12 20:43:31 SGT 2017 - RX packets:16278612090
> errors:10997152436 dropped:68 overruns:10997152436 frame:0
> 9) Thu Oct 12 20:43:36 SGT 2017 - RX packets:16281253727
> errors:11001834579 dropped:68 overruns:11001834579 frame:0
> 10) Thu Oct 12 20:43:41 SGT 2017 - RX packets:16283972622
> errors:11006374277 dropped:68 overruns:11006374277 frame:0
>
> ----
>
> Freak the CPU for better performance:
>
> cpufreq-set -r -g performance
>
> Results (nothing significant):
>
> ----
>
> :~# for i in `seq 1 10`;do echo "$i) `date`" - $(ifconfig ens4f1|
> egrep "RX"| egrep overruns;sleep 5);done
>
> 1) Thu Oct 12 21:53:07 SGT 2017 - RX packets:18506492788
> errors:14622639426 dropped:68 overruns:14622639426 frame:0
> 2) Thu Oct 12 21:53:12 SGT 2017 - RX packets:18509314581
> errors:14626750641 dropped:68 overruns:14626750641 frame:0
> 3) Thu Oct 12 21:53:17 SGT 2017 - RX packets:18511485458
> errors:14630268859 dropped:68 overruns:14630268859 frame:0
> 4) Thu Oct 12 21:53:22 SGT 2017 - RX packets:18514223562
> errors:14634547845 dropped:68 overruns:14634547845 frame:0
> 5) Thu Oct 12 21:53:27 SGT 2017 - RX packets:18516926578
> errors:14638745143 dropped:68 overruns:14638745143 frame:0
> 6) Thu Oct 12 21:53:32 SGT 2017 - RX packets:18519605412
> errors:14642929021 dropped:68 overruns:14642929021 frame:0
> 7) Thu Oct 12 21:53:37 SGT 2017 - RX packets:18522523560
> errors:14647108982 dropped:68 overruns:14647108982 frame:0
> 8) Thu Oct 12 21:53:42 SGT 2017 - RX packets:18525185869
> errors:14651577286 dropped:68 overruns:14651577286 frame:0
> 9) Thu Oct 12 21:53:47 SGT 2017 - RX packets:18527947266
> errors:14655961847 dropped:68 overruns:14655961847 frame:0
> 10) Thu Oct 12 21:53:52 SGT 2017 - RX packets:18530703288
> errors:14659988398 dropped:68 overruns:14659988398 frame:0
>
> ----
>
> Results using sar:
>
> ----
>
> :~# sar -n EDEV 5 3| egrep "(ens4f1|IFACE)"
>
> 11:17:43 PM IFACE rxerr/s txerr/s coll/s rxdrop/s
> txdrop/s txcarr/s rxfram/s rxfifo/s txfifo/s
> 11:17:48 PM ens4f1 360809.40 0.00 0.00 0.00
> 0.00 0.00 0.00 360809.40 0.00
> 11:17:53 PM ens4f1 382500.40 0.00 0.00 0.00
> 0.00 0.00 0.00 382500.40 0.00
> 11:17:58 PM ens4f1 353717.00 0.00 0.00 0.00
> 0.00 0.00 0.00 353717.00 0.00
> Average: ens4f1 365675.60 0.00 0.00 0.00
> 0.00 0.00 0.00 365675.60 0.00
>
> ----
> --
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