From: Nick Piggin <nickpiggin@yahoo.com.au>
Date: Wed, 14 Nov 2007 04:36:24 +1100

quoted text
> On Wednesday 14 November 2007 12:58, David Miller wrote:
> > I suspect the issue is about having a huge skb->data linear area for
> > TCP sends over loopback.  We're likely getting a much smaller
> > skb->data linear data area after the patch in question, the rest using
> > the sk_buff scatterlist pages which are a little bit more expensive to
> > process.
> 
> It didn't seem to be noticeable at 1 client. Unless scatterlist
> processing is going to cause cacheline bouncing, I don't see why this
> hurts more as you add CPUs?

Is your test system using HIGHMEM?

That's one thing the page vector in the sk_buff can do a lot,
kmaps.
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