Hi Dave,

David Miller [off-list ref] wrote on 01/15/2010 02:48:29 PM:

Re: [RFC] [PATCH] Optimize TCP sendmsg in favour of fast devices?

From: Krishna Kumar2 <redacted>
Date: Fri, 15 Jan 2010 14:50:04 +0530

quoted

I wonder if there is some other way to test it. I could test it on
the card I have, cxgbe, by ethtool F_SG off, and then testing
this patch with existing code (both with ethtool F_SG off)? Will
that be enough to get an idea, or I cannot assume this is
reasonable for real non-sg drivers? I am sure there is a
degradation, and mentioned that part as a "penalty" for those
drivers in my patch.

I think such a test would provide useful data by which to judge this
change.

I had to remove the F_SG flag from cxgb3 driver (using ethtool
didn't show any difference in performance since GSO was enabled
on the device due to register_netdev setting it). Testing show a
drop of 25% in performance with this patch for non-SG device,
the extra alloc/memcpy is showing up.

For the SG driver, I get a good performace gain (not anywhere
close to 25% though). What do you suggest?

Thanks,

- KK