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Message-ID: <20100912204552.GA2585@del.dom.local> Date: Sun, 12 Sep 2010 22:45:52 +0200 From: Jarek Poplawski <jarkao2@...il.com> To: David Miller <davem@...emloft.net> Cc: eric.dumazet@...il.com, netdev@...r.kernel.org Subject: Re: [PATCH net-next-2.6] net: pskb_expand_head() optimization On Sun, Sep 12, 2010 at 08:58:33AM -0700, David Miller wrote: > From: Jarek Poplawski <jarkao2@...il.com> > Date: Sun, 12 Sep 2010 12:45:34 +0200 > > > Then a few more questions: > > 1) if doubly linked lists really require such pskb_copying, isn't it > > all too costly? > > In the common case the data reference will be one, so we will not > copy. Even if so, one such a case on the fast path should hit performance, so it would need special reviewing. > > > 2) why skb_clone isn't enough instead of pskb_copy? > > Can't share the metadata. I'd really like to understand why the change in handling next/prev should affect more than skb pointers wrt. current sharing. > > > 3) since skb_clone has some cost too, why e.g. saving only the pointer > > to the tail of the list in skb_shared_info isn't enough? > > Then we won't get the rest of the advantages of using list_head such > as prefetching during traversals, automatic debugging facilities, et al. Right, we need to sum pros and cons. So, what's the pros? ;-) Jarek P. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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