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Date:   Fri, 30 Sep 2022 11:50:20 +0000
To:     Nick Child <>
Subject: Re: [PATCH v2 net-next 1/3] ibmveth: Copy tx skbs into a premapped buffer


This series was applied to netdev/net-next.git (master)
by David S. Miller <>:

On Wed, 28 Sep 2022 16:43:48 -0500 you wrote:
> Rather than DMA mapping and unmapping every outgoing skb, copy the skb
> into a buffer that was mapped during the drivers open function. Copying
> the skb and its frags have proven to be more time efficient than
> mapping and unmapping. As an effect, performance increases by 3-5
> Gbits/s.
> Allocate and DMA map one continuous 64KB buffer at `ndo_open`. This
> buffer is maintained until `ibmveth_close` is called. This buffer is
> large enough to hold the largest possible linnear skb. During
> `ndo_start_xmit`, copy the skb and all of it's frags into the continuous
> buffer. By manually linnearizing all the socket buffers, time is saved
> during memcpy as well as more efficient handling in FW.
> As a result, we no longer need to worry about the firmware limitation
> of handling a max of 6 frags. So, we only need to maintain 1 descriptor
> instead of 6 and can hardcode 0 for the other 5 descriptors during
> h_send_logical_lan.
> [...]

Here is the summary with links:
  - [v2,net-next,1/3] ibmveth: Copy tx skbs into a premapped buffer
  - [v2,net-next,2/3] ibmveth: Implement multi queue on xmit
  - [v2,net-next,3/3] ibmveth: Ethtool set queue support

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