net: add low latency socket poll
Adds an ndo_ll_poll method and the code that supports it. This method can be used by low latency applications to busy-poll Ethernet device queues directly from the socket code. sysctl_net_ll_poll controls how many microseconds to poll. Default is zero (disabled). Individual protocol support will be added by subsequent patches. Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com> Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com> Signed-off-by: Eliezer Tamir <eliezer.tamir@linux.intel.com> Acked-by: Eric Dumazet <edumazet@google.com> Tested-by: Willem de Bruijn <willemb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eliezer Tamir
David S. Miller
parent
af12fa6e46
commit
0602129286
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@ -50,6 +50,13 @@ The maximum number of packets that kernel can handle on a NAPI interrupt,
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it's a Per-CPU variable.
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Default: 64
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low_latency_poll
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----------------
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Low latency busy poll timeout. (needs CONFIG_NET_LL_RX_POLL)
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Approximate time in us to spin waiting for packets on the device queue.
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Recommended value is 50. May increase power usage.
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Default: 0 (off)
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rmem_default
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------------
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@ -971,6 +971,9 @@ struct net_device_ops {
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struct netpoll_info *info,
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gfp_t gfp);
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void (*ndo_netpoll_cleanup)(struct net_device *dev);
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#endif
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#ifdef CONFIG_NET_LL_RX_POLL
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int (*ndo_ll_poll)(struct napi_struct *dev);
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#endif
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int (*ndo_set_vf_mac)(struct net_device *dev,
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int queue, u8 *mac);
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@ -386,6 +386,7 @@ typedef unsigned char *sk_buff_data_t;
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* @no_fcs: Request NIC to treat last 4 bytes as Ethernet FCS
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* @dma_cookie: a cookie to one of several possible DMA operations
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* done by skb DMA functions
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* @napi_id: id of the NAPI struct this skb came from
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* @secmark: security marking
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* @mark: Generic packet mark
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* @dropcount: total number of sk_receive_queue overflows
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@ -500,8 +501,11 @@ struct sk_buff {
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/* 7/9 bit hole (depending on ndisc_nodetype presence) */
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kmemcheck_bitfield_end(flags2);
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#ifdef CONFIG_NET_DMA
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dma_cookie_t dma_cookie;
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#if defined CONFIG_NET_DMA || defined CONFIG_NET_LL_RX_POLL
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union {
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unsigned int napi_id;
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dma_cookie_t dma_cookie;
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};
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#endif
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#ifdef CONFIG_NETWORK_SECMARK
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__u32 secmark;
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@ -0,0 +1,148 @@
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/*
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* Low Latency Sockets
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* Copyright(c) 2013 Intel Corporation.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Author: Eliezer Tamir
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*
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* Contact Information:
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* e1000-devel Mailing List <e1000-devel@lists.sourceforge.net>
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*/
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/*
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* For now this depends on CONFIG_X86_TSC
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*/
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#ifndef _LINUX_NET_LL_POLL_H
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#define _LINUX_NET_LL_POLL_H
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#include <linux/netdevice.h>
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#include <net/ip.h>
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#ifdef CONFIG_NET_LL_RX_POLL
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struct napi_struct;
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extern unsigned long sysctl_net_ll_poll __read_mostly;
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/* return values from ndo_ll_poll */
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#define LL_FLUSH_FAILED -1
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#define LL_FLUSH_BUSY -2
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/* we don't mind a ~2.5% imprecision */
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#define TSC_MHZ (tsc_khz >> 10)
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static inline cycles_t ll_end_time(void)
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{
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return TSC_MHZ * ACCESS_ONCE(sysctl_net_ll_poll) + get_cycles();
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}
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static inline bool sk_valid_ll(struct sock *sk)
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{
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return sysctl_net_ll_poll && sk->sk_napi_id &&
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!need_resched() && !signal_pending(current);
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}
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static inline bool can_poll_ll(cycles_t end_time)
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{
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return !time_after((unsigned long)get_cycles(),
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(unsigned long)end_time);
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}
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static inline bool sk_poll_ll(struct sock *sk, int nonblock)
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{
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cycles_t end_time = ll_end_time();
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const struct net_device_ops *ops;
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struct napi_struct *napi;
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int rc = false;
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/*
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* rcu read lock for napi hash
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* bh so we don't race with net_rx_action
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*/
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rcu_read_lock_bh();
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napi = napi_by_id(sk->sk_napi_id);
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if (!napi)
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goto out;
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ops = napi->dev->netdev_ops;
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if (!ops->ndo_ll_poll)
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goto out;
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do {
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rc = ops->ndo_ll_poll(napi);
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if (rc == LL_FLUSH_FAILED)
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break; /* permanent failure */
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if (rc > 0)
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/* local bh are disabled so it is ok to use _BH */
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NET_ADD_STATS_BH(sock_net(sk),
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LINUX_MIB_LOWLATENCYRXPACKETS, rc);
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} while (skb_queue_empty(&sk->sk_receive_queue)
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&& can_poll_ll(end_time) && !nonblock);
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rc = !skb_queue_empty(&sk->sk_receive_queue);
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out:
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rcu_read_unlock_bh();
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return rc;
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}
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/* used in the NIC receive handler to mark the skb */
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static inline void skb_mark_ll(struct sk_buff *skb, struct napi_struct *napi)
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{
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skb->napi_id = napi->napi_id;
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}
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/* used in the protocol hanlder to propagate the napi_id to the socket */
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static inline void sk_mark_ll(struct sock *sk, struct sk_buff *skb)
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{
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sk->sk_napi_id = skb->napi_id;
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}
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#else /* CONFIG_NET_LL_RX_POLL */
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static inline cycles_t ll_end_time(void)
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{
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return 0;
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}
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static inline bool sk_valid_ll(struct sock *sk)
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{
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return false;
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}
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static inline bool sk_poll_ll(struct sock *sk, int nonblock)
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{
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return false;
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}
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static inline void skb_mark_ll(struct sk_buff *skb, struct napi_struct *napi)
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{
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}
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static inline void sk_mark_ll(struct sock *sk, struct sk_buff *skb)
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{
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}
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static inline bool can_poll_ll(cycles_t end_time)
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{
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return false;
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}
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#endif /* CONFIG_NET_LL_RX_POLL */
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#endif /* _LINUX_NET_LL_POLL_H */
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@ -229,6 +229,7 @@ struct cg_proto;
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* @sk_omem_alloc: "o" is "option" or "other"
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* @sk_wmem_queued: persistent queue size
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* @sk_forward_alloc: space allocated forward
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* @sk_napi_id: id of the last napi context to receive data for sk
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* @sk_allocation: allocation mode
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* @sk_sndbuf: size of send buffer in bytes
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* @sk_flags: %SO_LINGER (l_onoff), %SO_BROADCAST, %SO_KEEPALIVE,
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@ -324,6 +325,9 @@ struct sock {
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int sk_forward_alloc;
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#ifdef CONFIG_RPS
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__u32 sk_rxhash;
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#endif
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#ifdef CONFIG_NET_LL_RX_POLL
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unsigned int sk_napi_id;
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#endif
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atomic_t sk_drops;
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int sk_rcvbuf;
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@ -253,6 +253,7 @@ enum
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LINUX_MIB_TCPFASTOPENLISTENOVERFLOW, /* TCPFastOpenListenOverflow */
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LINUX_MIB_TCPFASTOPENCOOKIEREQD, /* TCPFastOpenCookieReqd */
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LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES, /* TCPSpuriousRtxHostQueues */
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LINUX_MIB_LOWLATENCYRXPACKETS, /* LowLatencyRxPackets */
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__LINUX_MIB_MAX
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};
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12
net/Kconfig
12
net/Kconfig
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@ -243,6 +243,18 @@ config NETPRIO_CGROUP
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Cgroup subsystem for use in assigning processes to network priorities on
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a per-interface basis
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config NET_LL_RX_POLL
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bool "Low Latency Receive Poll"
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depends on X86_TSC
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default n
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---help---
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Support Low Latency Receive Queue Poll.
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(For network card drivers which support this option.)
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When waiting for data in read or poll call directly into the the device driver
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to flush packets which may be pending on the device queues into the stack.
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If unsure, say N.
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config BQL
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boolean
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depends on SYSFS
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@ -733,6 +733,10 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
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new->vlan_tci = old->vlan_tci;
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skb_copy_secmark(new, old);
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#ifdef CONFIG_NET_LL_RX_POLL
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new->napi_id = old->napi_id;
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#endif
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}
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/*
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@ -139,6 +139,8 @@
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#include <net/tcp.h>
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#endif
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#include <net/ll_poll.h>
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static DEFINE_MUTEX(proto_list_mutex);
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static LIST_HEAD(proto_list);
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@ -2284,6 +2286,10 @@ void sock_init_data(struct socket *sock, struct sock *sk)
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sk->sk_stamp = ktime_set(-1L, 0);
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#ifdef CONFIG_NET_LL_RX_POLL
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sk->sk_napi_id = 0;
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#endif
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/*
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* Before updating sk_refcnt, we must commit prior changes to memory
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* (Documentation/RCU/rculist_nulls.txt for details)
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@ -19,6 +19,7 @@
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#include <net/ip.h>
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#include <net/sock.h>
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#include <net/net_ratelimit.h>
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#include <net/ll_poll.h>
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static int one = 1;
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@ -284,6 +285,15 @@ static struct ctl_table net_core_table[] = {
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.proc_handler = flow_limit_table_len_sysctl
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},
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#endif /* CONFIG_NET_FLOW_LIMIT */
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#ifdef CONFIG_NET_LL_RX_POLL
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{
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.procname = "low_latency_poll",
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.data = &sysctl_net_ll_poll,
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.maxlen = sizeof(unsigned long),
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.mode = 0644,
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.proc_handler = proc_doulongvec_minmax
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},
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#endif
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#endif /* CONFIG_NET */
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{
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.procname = "netdev_budget",
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@ -273,6 +273,7 @@ static const struct snmp_mib snmp4_net_list[] = {
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SNMP_MIB_ITEM("TCPFastOpenListenOverflow", LINUX_MIB_TCPFASTOPENLISTENOVERFLOW),
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SNMP_MIB_ITEM("TCPFastOpenCookieReqd", LINUX_MIB_TCPFASTOPENCOOKIEREQD),
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SNMP_MIB_ITEM("TCPSpuriousRtxHostQueues", LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES),
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SNMP_MIB_ITEM("LowLatencyRxPackets", LINUX_MIB_LOWLATENCYRXPACKETS),
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SNMP_MIB_SENTINEL
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};
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@ -104,6 +104,12 @@
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#include <linux/route.h>
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#include <linux/sockios.h>
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#include <linux/atalk.h>
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#include <net/ll_poll.h>
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#ifdef CONFIG_NET_LL_RX_POLL
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unsigned long sysctl_net_ll_poll __read_mostly;
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EXPORT_SYMBOL_GPL(sysctl_net_ll_poll);
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#endif
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static int sock_no_open(struct inode *irrelevant, struct file *dontcare);
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static ssize_t sock_aio_read(struct kiocb *iocb, const struct iovec *iov,
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