RFC: How to fix the NFS/iSCSI vs TSO problem

Rick Macklem rmacklem at uoguelph.ca
Tue Apr 1 00:41:45 UTC 2014

Jordan Hubbard wrote:
> On Mar 31, 2014, at 8:53 AM, Marcelo Araujo <araujobsdport at gmail.com>
> wrote:
> > I understand your concern about add more one sysctl, however maybe
> > we can
> > do something like ZFS does, if it detect the system is AMD and have
> > more
> > than X of RAM it enables some options by default, or a kind of
> > warning can
> > be displayed show the new sysctl option.
> > 
> > Of, course other people opinion will be very welcome.
> Why not simply enable (conditionally compile) it in only for the x64
> architecture?   If you’re on a 64 bit Intel architecture machine,
> chances are pretty good you’re also running hardware of reasonable
> recent vintage and aren’t significantly HW constrained.
I'm actually typing this on a single core amd64 with 2Gbytes of RAM, so
I think enabling it only for both 64bits and at least some # of Gbytes of
RAM would be better. (I agree that most amd64s will be relatively big
machines, but not all;-)

My biggest problem is that I have no way of testing this on a fairly
big amd64 server at this time and I'd be a lot more comfortable committing
a patch that has been tested this way. (I realize that Marcelo has been
running it for his benchmarks and that's a good start, but it isn't the
same as a heavily loaded server.)

I notice that Alexander is on the cc list and I've added Garrett, since
those are the two guys that have been doing a bunch of server testing
(and my thanks go to them for this). Maybe they will have a chance to
test this patch on a heavily loaded server?

Since I do want to test/debug the if_hw_tsomaxseg patch I have, I plan
on inquiring to see if I can use something like the netperf cluster
for this testing (in a couple of weeks when I get home).


> I think it’s also fair to say that if you’re providing NFS or iSCSI
> services on an i386 with 512M of memory or a similarly endowed ARM
> or PPC system, performance is not your first and primary concern.
>  You’re simply happy that it works at all. ;-)
> - Jordan

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