On Wednesday 14 November 2007 17:12, David Miller wrote: > From: Nick Piggin <[EMAIL PROTECTED]> > Date: Wed, 14 Nov 2007 04:36:24 +1100 > > > 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.
No, it's an x86-64, so no highmem. What's also interesting is that SLAB apparently doesn't have this condition. The first thing that sprung to mind is that SLAB caches order > 0 allocations, while SLUB does not. However if anything, that should actually favour the SLUB numbers if network is avoiding order > 0 allocations. I'm doing some oprofile runs now to see if I can get any more info. - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
