netdev - Re: [PATCH net-next V1] net: adjust net_device layout for cacheline usage

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Date:   Fri, 29 Jan 2021 04:50:13 +0000
From:   patchwork-bot+netdevbpf@...nel.org
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     dsahern@...il.com, netdev@...r.kernel.org, kuba@...nel.org,
        davem@...emloft.net, bpf@...r.kernel.org, eric.dumazet@...il.com,
        borkmann@...earbox.net, alexei.starovoitov@...il.com
Subject: Re: [PATCH net-next V1] net: adjust net_device layout for cacheline usage

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Tue, 26 Jan 2021 18:39:39 +0100 you wrote:
> The current layout of net_device is not optimal for cacheline usage.
> 
> The member adj_list.lower linked list is split between cacheline 2 and 3.
> The ifindex is placed together with stats (struct net_device_stats),
> although most modern drivers don't update this stats member.
> 
> The members netdev_ops, mtu and hard_header_len are placed on three
> different cachelines. These members are accessed for XDP redirect into
> devmap, which were noticeably with perf tool. When not using the map
> redirect variant (like TC-BPF does), then ifindex is also used, which is
> placed on a separate fourth cacheline. These members are also accessed
> during forwarding with regular network stack. The members priv_flags and
> flags are on fast-path for network stack transmit path in __dev_queue_xmit
> (currently located together with mtu cacheline).
> 
> [...]

Here is the summary with links:
  - [net-next,V1] net: adjust net_device layout for cacheline usage
    https://git.kernel.org/netdev/net-next/c/28af22c6c8df

You are awesome, thank you!
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