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Bug #10465

closed

possible routing performance regression due to non use of ip_tryforward

Added by David Burns over 4 years ago. Updated almost 4 years ago.

Status:
Resolved
Priority:
Normal
Assignee:
-
Category:
Routing
Target version:
2.5.0
Start date:
04/16/2020
Due date:
% Done:

0%

Estimated time:
Plus Target Version:
Release Notes:
Affected Version:
2.4.5
Affected Architecture:

Description

A few years back Netgate sponsored upstream enhancements to FreeBSD which replaced ip_fastforward() with ip_tryforward() - which subsequently appeared in pfSense 2.3.

Whilst researching FreeBSD tuning (https://bsdrp.net/documentation/examples/forwarding_performance_lab_of_a_pc_engines_apu2) I noticed the recommendation to disable ICMP redirects.
This requirement comes from a patch applied to FreeBSD in August 2018 to fix ICMP redirects ... FreeBSD 11 Stable patch https://svnweb.freebsd.org/base?view=revision&revision=338343

As far as I can tell pfSense 2.4.5 has both IPv4 & IPv6 ICMP redirects defaulting to on - which based on above patch would now appear to disable tryforward path:
net.inet.ip.redirect: 1
net.inet6.ip6.redirect: 1

The workaround is obviously trivial:
sysctl net.inet.ip.redirect=0
sysctl net.inet6.ip6.redirect=0

Like many of us I'm away from my office and so lack test equipment... so I did a rudimentary analysis based on CPU
Sample vmstat 2 output from APU2 (default) - test throughput ~85Mb/s WAN->LAN

procs  memory       page                    disks     faults         cpu
r b w  avm   fre   flt  re  pi  po    fr   sr md0 ad0   in    sy    cs us sy id
0 0 0 655M  3.4G     4   0   0   0     0    6   0   0 18750   319 38839  2 14 84
0 0 0 655M  3.4G     4   0   0   0     0    6   0   0 16177   276 33722  1 15 84
0 0 0 655M  3.4G     4   0   0   0     0    6   0   0 14841   139 31430  1 13 86
0 0 0 655M  3.4G     4   0   0   0     0    9   0   0 15865   109 33206  0 13 87
0 0 0 655M  3.4G     4   0   0   0     0    6   0   0 16218   130 33776  1 14 85
0 0 0 655M  3.4G     4   0   0   0     0    6   0   0 14252   109 30215  1 10 89
0 0 0 655M  3.4G     4   0   0   0     0    6   0   0 15339   106 32168  1 13 86

Sample vmstat 2 output from APU2 (ICMP redirects disabled) - test throughput ~85Mb/s WAN->LAN

procs  memory       page                    disks     faults         cpu
r b w  avm   fre   flt  re  pi  po    fr   sr md0 ad0   in    sy    cs us sy id
0 0 0 655M  3.4G     4   0   0   0     0    6   0   0 18644   111 37189  0 15 84
0 0 0 655M  3.4G     2   0   0   0     0    6   0   0 16840   129 34442  1 13 87
0 0 0 655M  3.4G     4   0   0   0     0    6   0   0 17776   118 36026  1 12 87
0 0 0 655M  3.4G     4   0   0   0     0    6   0   0 16221   109 33478  0 13 86
0 0 0 655M  3.4G     6   0   0   0     0    6   0   0 17251   127 35166  1 12 87
0 0 0 655M  3.4G     2   0   0   0     0    6   0   0 18232   136 37086  1 13 86
0 0 0 655M  3.4G     5   0   0   0     0    6   0   1 18724   202 37911  1 14 85

Not entirely scientific but shows a modest 1-2% CPU drop. Clearly for GbE bandwidths the improvement is likely to be larger.

Assuming these results can be confirmed then maybe sysctl defaults can be changed in future release?

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