tech-net archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

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

On Tue, Nov 22, 2011 at 12:41:13AM -0600, David Young wrote:
> On Mon, Nov 21, 2011 at 10:11:17PM +0100, Manuel Bouyer wrote:
> > On Mon, Nov 21, 2011 at 02:58:57PM -0600, Greg Oster wrote:
> > > Hi Manuel
> > > 
> > > Have there been issues with these patches that prevent them from being
> > > applied to -current and/or pulled up?
> > 
> > Nothing wrong AFAIK, I just got distracted.
> In the discussion of the patches, people seem to disagree how the
> patches work to improve the performance as they do, whether the patches
> are portable, and whether or not the whole patch is necessary or just
> the bus_dmamap_sync() part of it.  I hope our understanding improves
> before there is a commit. :-/

There are 2 parts: changes to the interrupt setup, and the reading of
receive descriptors.

I didn't see peoples having issues with the interrupt setup.

As for the discussion if a x86 CPU will reorder reads, I'm sure they do:
I've had troubles in Xen front/back driver because of this
(and there is explicit lfence() in the linux Xen drivers, because of this).

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

Home | Main Index | Thread Index | Old Index