From: Eric Dumazet <>
Date: Thu, 15 Sep 2016 09:33:02 -0700

> From: Eric Dumazet <>
> With large BDP TCP flows and lossy networks, it is very important
> to keep a low number of skbs in the write queue.
> RACK and SACK processing can perform a linear scan of it.
> We should avoid putting any payload in skb->head, so that SACK
> shifting can be done if needed.
> With this patch, we allow to pack ~0.5 MB per skb instead of
> the 64KB initially cooked at tcp_sendmsg() time.
> This gives a reduction of number of skbs in write queue by eight.
> tcp_rack_detect_loss() likes this.
> We still allow payload in skb->head for first skb put in the queue,
> to not impact RPC workloads.
> Signed-off-by: Eric Dumazet <>
> Cc: Yuchung Cheng <>


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