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>

diff --git a/Documentation/sysctl/net.txt b/Documentation/sysctl/net.txt
index c1f8640c2fc8818519e5840e72be92edcc8c98eb..85ab72dcdc3c9f61198555b56020f84edfe2554b 100644 (file)
--- a/Documentation/sysctl/net.txt
+++ b/Documentation/sysctl/net.txt
@@ -50,6 +50,13 @@ The maximum number of packets that kernel can handle on a NAPI interrupt,
 it's a Per-CPU variable.
 Default: 64
 
+low_latency_poll
+----------------
+Low latency busy poll timeout. (needs CONFIG_NET_LL_RX_POLL)
+Approximate time in us to spin waiting for packets on the device queue.
+Recommended value is 50. May increase power usage.
+Default: 0 (off)
+
 rmem_default
 ------------
 

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 39bbd462d68ed48c0646442bd2da93c09cba22d0..2ecb96d9a1e5ae4448014dd3872007f44a912f53 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -971,6 +971,9 @@ struct net_device_ops {
                                                     struct netpoll_info *info,
                                                     gfp_t gfp);
        void                    (*ndo_netpoll_cleanup)(struct net_device *dev);
+#endif
+#ifdef CONFIG_NET_LL_RX_POLL
+       int                     (*ndo_ll_poll)(struct napi_struct *dev);
 #endif
        int                     (*ndo_set_vf_mac)(struct net_device *dev,
                                                  int queue, u8 *mac);

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 9995834d2cb6b4050c607250870abda56858843b..400d82ae2b0312fadbc4e84b8e16a7fda946d9b8 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -386,6 +386,7 @@ typedef unsigned char *sk_buff_data_t;
  *     @no_fcs:  Request NIC to treat last 4 bytes as Ethernet FCS
  *     @dma_cookie: a cookie to one of several possible DMA operations
  *             done by skb DMA functions
+  *    @napi_id: id of the NAPI struct this skb came from
  *     @secmark: security marking
  *     @mark: Generic packet mark
  *     @dropcount: total number of sk_receive_queue overflows
@@ -500,8 +501,11 @@ struct sk_buff {
        /* 7/9 bit hole (depending on ndisc_nodetype presence) */
        kmemcheck_bitfield_end(flags2);
 
-#ifdef CONFIG_NET_DMA
-       dma_cookie_t            dma_cookie;
+#if defined CONFIG_NET_DMA || defined CONFIG_NET_LL_RX_POLL
+       union {
+               unsigned int    napi_id;
+               dma_cookie_t    dma_cookie;
+       };
 #endif
 #ifdef CONFIG_NETWORK_SECMARK
        __u32                   secmark;

diff --git a/include/net/ll_poll.h b/include/net/ll_poll.h
new file mode 100644 (file)
index 0000000..bc262f8
--- /dev/null
+++ b/include/net/ll_poll.h
@@ -0,0 +1,148 @@
+/*
+ * Low Latency Sockets
+ * Copyright(c) 2013 Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Author: Eliezer Tamir
+ *
+ * Contact Information:
+ * e1000-devel Mailing List <e1000-devel@lists.sourceforge.net>
+ */
+
+/*
+ * For now this depends on CONFIG_X86_TSC
+ */
+
+#ifndef _LINUX_NET_LL_POLL_H
+#define _LINUX_NET_LL_POLL_H
+
+#include <linux/netdevice.h>
+#include <net/ip.h>
+
+#ifdef CONFIG_NET_LL_RX_POLL
+
+struct napi_struct;
+extern unsigned long sysctl_net_ll_poll __read_mostly;
+
+/* return values from ndo_ll_poll */
+#define LL_FLUSH_FAILED                -1
+#define LL_FLUSH_BUSY          -2
+
+/* we don't mind a ~2.5% imprecision */
+#define TSC_MHZ (tsc_khz >> 10)
+
+static inline cycles_t ll_end_time(void)
+{
+       return TSC_MHZ * ACCESS_ONCE(sysctl_net_ll_poll) + get_cycles();
+}
+
+static inline bool sk_valid_ll(struct sock *sk)
+{
+       return sysctl_net_ll_poll && sk->sk_napi_id &&
+              !need_resched() && !signal_pending(current);
+}
+
+static inline bool can_poll_ll(cycles_t end_time)
+{
+       return !time_after((unsigned long)get_cycles(),
+                           (unsigned long)end_time);
+}
+
+static inline bool sk_poll_ll(struct sock *sk, int nonblock)
+{
+       cycles_t end_time = ll_end_time();
+       const struct net_device_ops *ops;
+       struct napi_struct *napi;
+       int rc = false;
+
+       /*
+        * rcu read lock for napi hash
+        * bh so we don't race with net_rx_action
+        */
+       rcu_read_lock_bh();
+
+       napi = napi_by_id(sk->sk_napi_id);
+       if (!napi)
+               goto out;
+
+       ops = napi->dev->netdev_ops;
+       if (!ops->ndo_ll_poll)
+               goto out;
+
+       do {
+
+               rc = ops->ndo_ll_poll(napi);
+
+               if (rc == LL_FLUSH_FAILED)
+                       break; /* permanent failure */
+
+               if (rc > 0)
+                       /* local bh are disabled so it is ok to use _BH */
+                       NET_ADD_STATS_BH(sock_net(sk),
+                                        LINUX_MIB_LOWLATENCYRXPACKETS, rc);
+
+       } while (skb_queue_empty(&sk->sk_receive_queue)
+                       && can_poll_ll(end_time) && !nonblock);
+
+       rc = !skb_queue_empty(&sk->sk_receive_queue);
+out:
+       rcu_read_unlock_bh();
+       return rc;
+}
+
+/* used in the NIC receive handler to mark the skb */
+static inline void skb_mark_ll(struct sk_buff *skb, struct napi_struct *napi)
+{
+       skb->napi_id = napi->napi_id;
+}
+
+/* used in the protocol hanlder to propagate the napi_id to the socket */
+static inline void sk_mark_ll(struct sock *sk, struct sk_buff *skb)
+{
+       sk->sk_napi_id = skb->napi_id;
+}
+
+#else /* CONFIG_NET_LL_RX_POLL */
+
+static inline cycles_t ll_end_time(void)
+{
+       return 0;
+}
+
+static inline bool sk_valid_ll(struct sock *sk)
+{
+       return false;
+}
+
+static inline bool sk_poll_ll(struct sock *sk, int nonblock)
+{
+       return false;
+}
+
+static inline void skb_mark_ll(struct sk_buff *skb, struct napi_struct *napi)
+{
+}
+
+static inline void sk_mark_ll(struct sock *sk, struct sk_buff *skb)
+{
+}
+
+static inline bool can_poll_ll(cycles_t end_time)
+{
+       return false;
+}
+
+#endif /* CONFIG_NET_LL_RX_POLL */
+#endif /* _LINUX_NET_LL_POLL_H */

diff --git a/include/net/sock.h b/include/net/sock.h
index 66772cf8c3c528c86104684ca3cf1ac8c5ccfd85..ac8e1818380c2c2a669cd9725dd4f018d86092b5 100644 (file)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -229,6 +229,7 @@ struct cg_proto;
   *    @sk_omem_alloc: "o" is "option" or "other"
   *    @sk_wmem_queued: persistent queue size
   *    @sk_forward_alloc: space allocated forward
+  *    @sk_napi_id: id of the last napi context to receive data for sk
   *    @sk_allocation: allocation mode
   *    @sk_sndbuf: size of send buffer in bytes
   *    @sk_flags: %SO_LINGER (l_onoff), %SO_BROADCAST, %SO_KEEPALIVE,
@@ -324,6 +325,9 @@ struct sock {
        int                     sk_forward_alloc;
 #ifdef CONFIG_RPS
        __u32                   sk_rxhash;
+#endif
+#ifdef CONFIG_NET_LL_RX_POLL
+       unsigned int            sk_napi_id;
 #endif
        atomic_t                sk_drops;
        int                     sk_rcvbuf;

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index df2e8b4f9c033f70f7115aeb1b7a846996f52a0a..26cbf76f8058535484180d6480444b5d9051bfe5 100644 (file)
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -253,6 +253,7 @@ enum
        LINUX_MIB_TCPFASTOPENLISTENOVERFLOW,    /* TCPFastOpenListenOverflow */
        LINUX_MIB_TCPFASTOPENCOOKIEREQD,        /* TCPFastOpenCookieReqd */
        LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES, /* TCPSpuriousRtxHostQueues */
+       LINUX_MIB_LOWLATENCYRXPACKETS,          /* LowLatencyRxPackets */
        __LINUX_MIB_MAX
 };
 

diff --git a/net/Kconfig b/net/Kconfig
index 523e43e6da1b9a66449b7e6d0dc5121602741239..d6a9ce6e18007793d4bbc7a4f5a35d2cf3abe7d4 100644 (file)
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -243,6 +243,18 @@ config NETPRIO_CGROUP
          Cgroup subsystem for use in assigning processes to network priorities on
          a per-interface basis
 
+config NET_LL_RX_POLL
+       bool "Low Latency Receive Poll"
+       depends on X86_TSC
+       default n
+       ---help---
+         Support Low Latency Receive Queue Poll.
+         (For network card drivers which support this option.)
+         When waiting for data in read or poll call directly into the the device driver
+         to flush packets which may be pending on the device queues into the stack.
+
+         If unsure, say N.
+
 config BQL
        boolean
        depends on SYSFS

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 73f57a0e15234a99a3dc64094ff56b28200de57d..4a4181e16c1a22fc0be2b220a6652bfa42fe4530 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -733,6 +733,10 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
        new->vlan_tci           = old->vlan_tci;
 
        skb_copy_secmark(new, old);
+
+#ifdef CONFIG_NET_LL_RX_POLL
+       new->napi_id    = old->napi_id;
+#endif
 }
 
 /*

diff --git a/net/core/sock.c b/net/core/sock.c
index 88868a9d21da54761a09b2ecaf0b88766190152f..788c0da5eed17fedee804c1654bff2b33d7d0261 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -139,6 +139,8 @@
 #include <net/tcp.h>
 #endif
 
+#include <net/ll_poll.h>
+
 static DEFINE_MUTEX(proto_list_mutex);
 static LIST_HEAD(proto_list);
 
@@ -2284,6 +2286,10 @@ void sock_init_data(struct socket *sock, struct sock *sk)
 
        sk->sk_stamp = ktime_set(-1L, 0);
 
+#ifdef CONFIG_NET_LL_RX_POLL
+       sk->sk_napi_id          =       0;
+#endif
+
        /*
         * Before updating sk_refcnt, we must commit prior changes to memory
         * (Documentation/RCU/rculist_nulls.txt for details)

diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 741db5fc78066dd7938a57718eacb27330de2548..4b48f39582b02b36352f70e262c6239b5dc43170 100644 (file)
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -19,6 +19,7 @@
 #include <net/ip.h>
 #include <net/sock.h>
 #include <net/net_ratelimit.h>
+#include <net/ll_poll.h>
 
 static int one = 1;
 
@@ -284,6 +285,15 @@ static struct ctl_table net_core_table[] = {
                .proc_handler   = flow_limit_table_len_sysctl
        },
 #endif /* CONFIG_NET_FLOW_LIMIT */
+#ifdef CONFIG_NET_LL_RX_POLL
+       {
+               .procname       = "low_latency_poll",
+               .data           = &sysctl_net_ll_poll,
+               .maxlen         = sizeof(unsigned long),
+               .mode           = 0644,
+               .proc_handler   = proc_doulongvec_minmax
+       },
+#endif
 #endif /* CONFIG_NET */
        {
                .procname       = "netdev_budget",

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 2a5bf86d241518816bf753c76764f3cb8837233f..6577a1149a47c17853e8c7e0e3daa267ef16d1cd 100644 (file)
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -273,6 +273,7 @@ static const struct snmp_mib snmp4_net_list[] = {
        SNMP_MIB_ITEM("TCPFastOpenListenOverflow", LINUX_MIB_TCPFASTOPENLISTENOVERFLOW),
        SNMP_MIB_ITEM("TCPFastOpenCookieReqd", LINUX_MIB_TCPFASTOPENCOOKIEREQD),
        SNMP_MIB_ITEM("TCPSpuriousRtxHostQueues", LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES),
+       SNMP_MIB_ITEM("LowLatencyRxPackets", LINUX_MIB_LOWLATENCYRXPACKETS),
        SNMP_MIB_SENTINEL
 };
 

diff --git a/net/socket.c b/net/socket.c
index 3ebdcb805c51c6c75c34854565b7e468d2e7c8c0..21fd29f63ed241cfbde465879c59182f22f472cd 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -104,6 +104,12 @@
 #include <linux/route.h>
 #include <linux/sockios.h>
 #include <linux/atalk.h>
+#include <net/ll_poll.h>
+
+#ifdef CONFIG_NET_LL_RX_POLL
+unsigned long sysctl_net_ll_poll __read_mostly;
+EXPORT_SYMBOL_GPL(sysctl_net_ll_poll);
+#endif
 
 static int sock_no_open(struct inode *irrelevant, struct file *dontcare);
 static ssize_t sock_aio_read(struct kiocb *iocb, const struct iovec *iov,