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Re: NetBSD 5.1 TCP performance issue (lots of ACK)

On Sat, Oct 22, 2011 at 02:43:05PM -0400, Thor Lancelot Simon wrote:
> On Sat, Oct 22, 2011 at 03:21:34PM +0100, Matthias Scheler wrote:
> > On Mon, Oct 17, 2011 at 06:03:18PM +0200, Manuel Bouyer wrote:
> > > I've been playing with glusterfs a bit today, and found some performance
> > > differences between NetBSD and linux, which I tracked down to our TCP
> > > stack. Basically, between a NetBSD/linux pair, performances are much
> > > better than between 2 NetBSD hosts.
> > 
> > What kind of network interfaces have these machines? And are you really
> > using NetBSD 5.1 or NetBSD 5.1_STABLE? Have you enable hardware
> > checksums under NetBSD? Linux turns them on by default.
> Not sure this is really relevant -- Manuel has pointed out what seems
> like it must be a serious issue with the TCP stack, namely its generation
> of huge numbers of ACKs for data flows where the Linux stack ACKs about
> as often as one would expect.

I think this was in a private mail to Greg Troxel, but I double-checked
this watching port counters on the cisco switch, and from the
output of netstat -s on both hosts after a clean boot and a single run of
the test.

Manuel Bouyer <>
     NetBSD: 26 ans d'experience feront toujours la difference

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