[ofa-general] Re: [PATCH 00/10] Implement batching skb API

On Fri, 20 Jul 2007 13:00:25 +0530
Krishna Kumar2 [off-list ref] wrote:

Stephen Hemminger [off-list ref] wrote on 07/20/2007
12:48:48 PM:

quoted

You may see worse performance with batching in the real world when
running over WAN's.  Like TSO, batching will generate back to back packet
trains that are subject to multi-packet synchronized loss. The problem is

that

quoted

intermediate router queues are often close to full, and when a long

string

quoted

of packets arrives back to back only the first ones will get in, the rest
get dropped.  Normal sends have at least minimal pacing so they are less
likely do get synchronized drop.

Hi Stephen,

OK. The difference that I could see is that in existing code, the "minimal
pacing" also could lead to (possibly slighly lesser) loss since sends are
quick iterations at the IP layer, while in batching sends are iterative at
the driver layer.

Is it an issue ? Any suggestions ?

Not an immediate issue, but it is the kind of thing that could cause performance
regression reports if it was used on every interface by default.