kern/154428: xn0 network interface and PF - Massive performance drop

[Colin Percival]

The following reply was made to PR kern/154428; it has been noted by GNATS.

From: Colin Percival <cperciva at freebsd.org>
To: Alex <joovke at joovke.com>
Cc: freebsd-xen at freebsd.org, bug-followup at FreeBSD.org
Subject: Re: kern/154428: xn0 network interface and PF - Massive performance
 drop
Date: Sat, 12 Feb 2011 20:31:07 -0800

 On 02/12/11 20:18, Alex wrote:
 > Fixed by net.inet.tcp.tso: 1 -> 0
 > 
 > but why?? found this by trial an error.  setting net.inet.tcp.tso to 0
 > with pf enabled gives good performance, if i set it to 1, speeds plumet
 > to below dialup!
 
 There have been problems with Xen and TSO in the past relating to how much
 data gets handed off to the hypervisor at once... why this would cause issues
 only with PF, I have no idea, though.
 
 -- 
 Colin Percival
 Security Officer, FreeBSD | freebsd.org | The power to serve
 Founder / author, Tarsnap | tarsnap.com | Online backups for the truly paranoid