On Wed, May 26, 2004 at 10:43:10AM -0700, Michael Chan wrote:
>
> > [...] is there a good reason why the tg3 driver
> > uses the on-chip SRAM send ring by default instead of the
> > host send ring?[...]
>
> I can only speak for the Broadcom bcm5700 driver. We used to use NIC
> send BDs by default before zero copy transmit and TSO were implemented
> in the kernel. Using only one BD per packet at that time, we found that
> performance on some machines were sometimes slightly better. Especially
> with logic to save some PIO when some of the fields in the BD have not
> changed. The driver has now been changed to use host send BDs to perform
> better with zero copy and especially TSO where you may need many BDs per
> packet. I would recommend tg3 to make the switch also.
Ah, it's precisely the zero copy case I'm interested in. I've measured
2 to 3 BDs per packet under my load.
Greg.
--
Greg Banks, R&D Software Engineer, SGI Australian Software Group.
I don't speak for SGI.
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