0602129286
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>
149 lines
3.3 KiB
C
149 lines
3.3 KiB
C
/*
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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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