Messages in this thread | | | From | Nick Piggin <> | Subject | Re: 2.6.24-rc2: Network commit causes SLUB performance regression with tbench | Date | Wed, 14 Nov 2007 05:14:27 +1100 |
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On Wednesday 14 November 2007 17:12, David Miller wrote: > From: Nick Piggin <nickpiggin@yahoo.com.au> > 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 linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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