From: Shirley Ma <[EMAIL PROTECTED]>
Date: Tue, 15 May 2007 14:22:57 -0700

>       I just wonder without TSO support in HW, how much benefit we
> can get by pushing GSO from interface layer to device layer besides
> we can do multiple packets in IPoIB.

I bet the gain is non-trivial.

I'd say about half of the gain from TSO comes from only calling down
into the driver from TCP one time as opposed to N times.  That's
the majority of the "CPU work" involved in TCP sending.

The rest of the gain comes from only transmitting the packet headers
once rather than N times, which conserves I/O bus bandwidth.

GSO will not help the case of lots of UDP applications sending
small packets, or something like that.  An efficient qdisc-->driver
transfer during netif_wake_queue() could help solve some of that,
as is being discussed here.
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