[PATCH 1/4] net: skb_orphan on dev_hard_start_xmit
rusty at rustcorp.com.au
Mon Jun 1 08:27:28 EDT 2009
On Sat, 30 May 2009 12:41:00 am Eric Dumazet wrote:
> Rusty Russell a écrit :
> > DaveM points out that there are advantages to doing it generally (it's
> > more likely to be on same CPU than after xmit), and I couldn't find
> > any new starvation issues in simple benchmarking here.
> If really no starvations are possible at all, I really wonder why some
> guys added memory accounting to UDP flows. Maybe they dont run "simple
> benchmarks" but real apps ? :)
Well, without any accounting at all you could use quite a lot of memory as
there are many places packets can be queued.
> For TCP, I agree your patch is a huge benefit, since its paced by remote
> ACKS and window control
I doubt that. There'll be some cache friendliness, but I'm not sure it'll be
measurable, let alone "huge". It's the win to drivers which don't have a
timely and batching tx free mechanism which I aim for.
> , but an UDP sender will likely be able to saturate
> a link.
I couldn't see any difference in saturation here (with default scheduler and an
100MBit e1000e). Two reasons come to mind: firstly, only the hardware queue is
unregulated: the tx queue is still accounted. And when you add scheduling to
the mix, I can't in practice cause starvation of other senders.
Hope that clarifies,
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