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FS#1852 - BT Home Hub 5A - 18.06 and snapshots - Drop in maximum WAN to LAN throughput #7360

openwrt-bot opened this issue Sep 17, 2018 · 5 comments


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@openwrt-bot openwrt-bot commented Sep 17, 2018


I observed recently there has been a drop off in maximum throughput from WAN to LAN ports on Home Hub 5A. I don't have 100 Mbps VDSL2 connection, so I can't verify whether the same drop is visible from DSL to LAN port.

The issue is old snapshots were capable of 130 Mbps and LEDE 17.01 (k4.4) could manage 110 Mbps. However, 18.06.1 (k4.9) can only manage 80+ Mbps.....

I don't possess any snapshots between 9 Jan 2018 to 25 may 2018, and so cannot determine which commit may have caused this sudden drop in throughput.

Running iperf3 on Windows laptop in server mode connected to WAN port.
Running iperf3 on another Windows laptop in client mode connected to LAN port.

iperf3 results: (Down/Upload Mbps)

SMP enabled:
r3386 (eth1.2) 11 Feb 2017: 149/98 Mbps

r5172 26 Oct 2017: 148/138 Mbps
r5702 9 Jan 2018: 138/130 Mbps

I think switch to kernel 4.14 - 17 May 2018

r7044 (k4.14) 25 May 2018 iperf3: 81/78 Mbps without flow offloading
r8065 (k4.14) 17 Sep 2018 iperf3: 75/71 Mbps without flow offloading

17.01.4 (k4.4, no SMP) Oct 2017 104 mbps, iperf3: 115/106 Mbps
17.01.6 (k4.4, no SMP) Sep 2018 iperf3: 112/104 Mbps

18.06.1 (k4.9) Aug 2018 83 mbps, iperf3: 85/78 Mbps

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@openwrt-bot openwrt-bot commented Oct 6, 2018


fyi, with the help of another user, maurer, on the ebilan forum, we're close to identifying the commit(s) that has caused the drop in WAN to LAN throughput on HH5A.

Narrowed down to date range 26 Feb to 3 Mar 2018 at time of writing:

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@openwrt-bot openwrt-bot commented Oct 6, 2018


Subject to review, we think we may have identified the commit which has caused the WAN to LAN throughput to drop suddenly on HH5A.

28 Feb 2018:
netifd: update to the latest version, rewrite RPS/XPS...


20180228 Openwrt r6330-810659a D 135 Mbps, U 126 Mbps D 134 Mbps, U 141 Mbps D 149 Mbps, U 139 Mbps (reflashed & retested)

20180228 Openwrt r6331-916e33f netifd update to the latest version, rewrite RPSXPS
D 80.9 Mbps, U 93.4? Mbps
D 85.0 Mbps, U 79.9 Mbps (reflashed & retested)

I executed this command and rebooted the Home Hub 5A as suggested by 'maurer'

rm /etc/hotplug.d/net/20-smp-tune

There is an improvement but the figures are still lower than what was seen before the above mentioned commit was applied:

openwrt-r6331-916e33f - netifd update to the latest version, rewrite RPSXPS
Before: D 85.0 Mbps, U 79.9 Mbps
After: D 113 Mbps, U 108 Mbps

openwrt 18.06.1
Before: D 87.8 Mbps, U 81.1 Mbps
After: D 116 Mbps Mbps, U 103 Mbps

Full iperf3 test results included below for completeness:

LEDE 17.01.6 D 114 Mbps, U 105 Mbps

20180507 OpenWrt SNAPSHOT r6856-ef19747 k4.9.96
D 91.4 Mbps, U 88.8 Mbps
D 91.5 Mbps, U 88.0 Mbps

20180420 OpenWrt SNAPSHOT r6740-74a0d8c k4.9.91
D 85.8 Mbps, U 81.8 Mbps

20180315 OpenWrt SNAPSHOT r6460-bf4aa52 k4.9.91
D 94.8 Mbps, U 86.2 Mbps

20180306 OpenWrt SNAPSHOT r6386-d84ac78 k4.9.85
D 85.1. Mbps, U 81.9 Mbps

20180303 OpenWrt SNAPSHOT r6374-5af85da k4.9.85
D 85.6 Mbps, U 79.2 Mbps

openwrt-k4.9.85bump OpenWrt SNAPSHOT r6374-5af85da k4.9.85 (suspect bad build)
D 84.3 Mbps, U 79.1 Mbps

Openwrt r6373-5af85da kernel bump 4.9 to 4.9.85 (Rebuilt image)
D 87.7 Mbps, U 79.1 Mbps

openwrt-deactivateASLR OpenWrt SNAPSHOT r6373-45ae5c2 k4.9.82 (suspect bad build)
D 88.3 Mbps, U 83.5 Mbps

Openwrt r6373-45ae5c2 lantiq Deactivate ASLR support for some applications (rebuilt image)
D 90.3 Mbps, U 83.9 Mbps

openwrt-ltq-vmmcCFLAGS OpenWrt SNAPSHOT r6372-d67b3d0 k4.9.82 (suspect bad build)
D 87.4 Mbps, U 80.2 Mbps

OpenWrt SNAPSHOT r6365-45fdb12 k4.9.82 (suspect bad build)
D 88.9 Mbps, U 83 Mbps

openwrt-r6365-45fdb12 Add kernel configuration options (Rebuilt image)
D 88.7 Mbps, U 81.2 Mbps

20180228 Openwrt r6331-916e33f netifd update to the latest version, rewrite RPSXPS
D 80.9 Mbps, U 93.4 Mbps
D 85.0 Mbps, U 79.9 Mbps (reflashed & retested)

20180228 Openwrt r6330-810659a ag71xx Move timestamp struct member outside of struct
D 135 Mbps, U 126 Mbps
D 134 Mbps, U 141 Mbps
D 149 Mbps, U 139 Mbps (reflashed & retested)

20180226 OpenWrt SNAPSHOT r6323-a49f656 k4.9.82
D 135 Mbps, U 145 Mbps

20180223 ?? OpenWrt SNAPSHOT r6323-a49f656 k4.9.82 (Update: Not 20180223)
D 135 Mbps, U 146 Mbps

20171223 OpenWrt SNAPSHOT r5608-9495263 k4.9.70
D 126 Mbps, U 142 Mbps

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@openwrt-bot openwrt-bot commented Oct 7, 2018


More iperf3 speed test results including very latest snapshot.

using ethernet and 300Mbps 5 GHz Wireless N/40MHz
Red WAN to yellow LAN or wifi.
Server connected to WAN port.
Windows laptop with Atheros AR5B22 2x2 dual band wifi card

17.01.4 eth D 110 Mbps, U 101 Mbps N/40MHz D 82.6 Mbps, U 99 Mbps

eth D 109 Mbps, U 100 Mbps
N/40MHz D 84.1 Mbps, U 100 Mbps

18.06.1 (k 4.9)
eth D 79.3 Mbps, U 74.3 Mbps
N/40MHz D 71.8 Mbps, U 81.4? Mbps

18.06.1 (rm /etc/hotplug.d/net/20-smp-tune)
eth D 106 Mbps, U 94.9 Mbps
N/40MHz D 67.9 Mbps, U 87.4 Mbps

r8235 snapshot (7 Oct 2018) (k 4.14)
eth D 73.1 Mbps, U 70.0 Mbps
N/40MHz D 44??? Mbps, U 78.1 Mbps

r8235 flow offloading
eth D 123 mbps, U 135 Mbps
N/40 MHz D 85.8?? Mbps, U 103 Mbps

r8235 flow offloading + rm /etc/hotplug.d/net/20-smp-tune
eth D 151 Mbps, U 152 Mbps
N/40 MHz D 88.4?? Mbps, U 103 Mbps

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@openwrt-bot openwrt-bot commented Oct 8, 2018


'maurer' compiled a 18.06.1 sysupgrade image without the above mentioned commit.


OpenWrt 18.06.1 r7258-5eb055306f (maurer) with LuCI eth D 142 Mbps, U 143 Mbps N/40MHz D 70 Mbps, U 91 Mbps

The WAN to LAN ethernet speeds are much improved.

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@openwrt-bot openwrt-bot commented Oct 31, 2019


Ooops. It's been over a year and I had forgotten I had opened this older ticket !

See newly opened ticket 2573 for latest update on this bug.

Ticket to be closed.

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