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Date: Mon, 23 Apr 2012 21:13:58 -0400 From: Neal Cardwell <ncardwell@...gle.com> To: Eric Dumazet <eric.dumazet@...il.com> Cc: David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>, Tom Herbert <therbert@...gle.com>, Maciej Żenczykowski <maze@...gle.com>, Ilpo Järvinen <ilpo.jarvinen@...sinki.fi> Subject: Re: [PATCH net-next] tcp: introduce tcp_try_coalesce On Mon, Apr 23, 2012 at 1:11 PM, Eric Dumazet <eric.dumazet@...il.com> wrote: > From: Eric Dumazet <edumazet@...gle.com> > > commit c8628155ece3 (tcp: reduce out_of_order memory use) took care of > coalescing tcp segments provided by legacy devices (linear skbs) > > We extend this idea to fragged skbs, as their truesize can be heavy. > > ixgbe for example uses 256+1024+PAGE_SIZE/2 = 3328 bytes per segment. > > Use this coalescing strategy for receive queue too. > > This contributes to reduce number of tcp collapses, at minimal cost, and > reduces memory overhead and packets drops. The mechanics look solid, but I'm a little concerned about the potential added overhead for the new case where tcp_try_coalesce() does a skb_copy_bits() for in-order data that it is coalescing at the end of the sk_receive_queue. Do you have any performance numbers for this case to help suggest whether this added copy is a concern? neal -- 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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