netdev - [PATCH bpf-next 5/9] xsk: add busy-poll support for {recv,send}msg()

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Date:   Thu, 12 Nov 2020 12:40:37 +0100
From:   Björn Töpel <bjorn.topel@...il.com>
To:     netdev@...r.kernel.org, bpf@...r.kernel.org
Cc:     Björn Töpel <bjorn.topel@...el.com>,
        magnus.karlsson@...el.com, ast@...nel.org, daniel@...earbox.net,
        maciej.fijalkowski@...el.com, sridhar.samudrala@...el.com,
        jesse.brandeburg@...el.com, qi.z.zhang@...el.com, kuba@...nel.org,
        edumazet@...gle.com, jonathan.lemon@...il.com, maximmi@...dia.com
Subject: [PATCH bpf-next 5/9] xsk: add busy-poll support for {recv,send}msg()

From: Björn Töpel <bjorn.topel@...el.com>

Wire-up XDP socket busy-poll support for recvmsg() and sendmsg(). If
the XDP socket prefers busy-polling, make sure that no wakeup/IPI is
performed.

Signed-off-by: Björn Töpel <bjorn.topel@...el.com>
---
 net/xdp/xsk.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 2e5b9f27c7a3..00663390a4a8 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -23,6 +23,7 @@
 #include <linux/netdevice.h>
 #include <linux/rculist.h>
 #include <net/xdp_sock_drv.h>
+#include <net/busy_poll.h>
 #include <net/xdp.h>
 
 #include "xsk_queue.h"
@@ -460,6 +461,16 @@ static int __xsk_sendmsg(struct sock *sk)
 	return xs->zc ? xsk_zc_xmit(xs) : xsk_generic_xmit(sk);
 }
 
+static bool xsk_no_wakeup(struct sock *sk)
+{
+#ifdef CONFIG_NET_RX_BUSY_POLL
+	/* Prefer busy-polling, skip the wakeup. */
+	return sk->sk_prefer_busy_poll && sk->sk_ll_usec && sk->sk_napi_id >= MIN_NAPI_ID;
+#else
+	return false;
+#endif
+}
+
 static int xsk_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
 {
 	bool need_wait = !(m->msg_flags & MSG_DONTWAIT);
@@ -472,6 +483,12 @@ static int xsk_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
 	if (unlikely(need_wait))
 		return -EOPNOTSUPP;
 
+	if (sk_can_busy_loop(sk))
+		sk_busy_loop(sk, 1); /* only support non-blocking sockets */
+
+	if (xsk_no_wakeup(sk))
+		return 0;
+
 	pool = xs->pool;
 	if (pool->cached_need_wakeup & XDP_WAKEUP_TX)
 		return __xsk_sendmsg(sk);
@@ -493,6 +510,12 @@ static int xsk_recvmsg(struct socket *sock, struct msghdr *m, size_t len, int fl
 	if (unlikely(need_wait))
 		return -EOPNOTSUPP;
 
+	if (sk_can_busy_loop(sk))
+		sk_busy_loop(sk, 1); /* only support non-blocking sockets */
+
+	if (xsk_no_wakeup(sk))
+		return 0;
+
 	if (xs->pool->cached_need_wakeup & XDP_WAKEUP_RX && xs->zc)
 		return xsk_wakeup(xs, XDP_WAKEUP_RX);
 	return 0;
-- 
2.27.0