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Message-ID: <2965be9f-72b8-4972-0580-f96b2a562018@iogearbox.net> Date: Tue, 17 Oct 2023 10:52:39 +0200 From: Daniel Borkmann <daniel@...earbox.net> To: Coco Li <lixiaoyan@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Eric Dumazet <edumazet@...gle.com>, Neal Cardwell <ncardwell@...gle.com>, Mubashir Adnan Qureshi <mubashirq@...gle.com>, Paolo Abeni <pabeni@...hat.com> Cc: netdev@...r.kernel.org, Chao Wu <wwchao@...gle.com>, Wei Wang <weiwan@...gle.com>, David Ahern <dsahern@...nel.org> Subject: Re: [PATCH v2 net-next 4/5] net-device: reorganize net_device fast path variables Hi Coco, Thanks for looking into this, awesome work! On 10/17/23 3:47 AM, Coco Li wrote: > Reorganize fast path variables on tx-txrx-rx order > Fastpath variables end after npinfo. > > Below data generated with pahole on x86 architecture. > > Fast path variables span cache lines before change: 12 > Fast path variables span cache lines after change: 4 > > Signed-off-by: Coco Li <lixiaoyan@...gle.com> > Suggested-by: Eric Dumazet <edumazet@...gle.com> > Reviewed-by: David Ahern <dsahern@...nel.org> > --- > include/linux/netdevice.h | 99 ++++++++++++++++++++------------------- > 1 file changed, 52 insertions(+), 47 deletions(-) > > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h > index 1c7681263d302..d72b71b76bf82 100644 > --- a/include/linux/netdevice.h > +++ b/include/linux/netdevice.h > @@ -2053,6 +2053,58 @@ enum netdev_ml_priv_type { > */ > > struct net_device { > + /* Caacheline organization can be found documented in tiny nit: typo > + * Documentation/networking/net_cachelines/net_device.rst. I think this doc is not based on current struct net_device as I saw some members in there which are not in net_device anymore today? For the doc, please document also tcx_ingress member as fastpath_rx_access (sch_handle_ingress) and tcx_egress member as fastpath_tx_access (sch_handle_egress). > + * Please update the document when adding new fields. > + */ > + > + /* TX read-mostly hotpath */ > + unsigned long long priv_flags; > + const struct net_device_ops *netdev_ops; > + const struct header_ops *header_ops; > + struct netdev_queue *_tx; > + unsigned int real_num_tx_queues; > + unsigned int gso_max_size; > + unsigned int gso_ipv4_max_size; > + u16 gso_max_segs; > + s16 num_tc; > + /* Note : dev->mtu is often read without holding a lock. > + * Writers usually hold RTNL. > + * It is recommended to use READ_ONCE() to annotate the reads, > + * and to use WRITE_ONCE() to annotate the writes. > + */ > + unsigned int mtu; > + unsigned short needed_headroom; > + struct netdev_tc_txq tc_to_txq[TC_MAX_QUEUE]; > +#ifdef CONFIG_XPS > + struct xps_dev_maps __rcu *xps_maps[XPS_MAPS_MAX]; > +#endif > +#ifdef CONFIG_NETFILTER_EGRESS > + struct nf_hook_entries __rcu *nf_hooks_egress; > +#endif As mentioned above, please also add tcx_egress to TX read-mostly hotpath cacheline. Thanks, Daniel
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