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Message-ID: <20250109003436.2829560-1-sdf@fomichev.me>
Date: Wed, 8 Jan 2025 16:34:36 -0800
From: Stanislav Fomichev <sdf@...ichev.me>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net,
edumazet@...gle.com,
kuba@...nel.org,
pabeni@...hat.com,
linux-kernel@...r.kernel.org,
bpf@...r.kernel.org,
horms@...nel.org,
ast@...nel.org,
daniel@...earbox.net,
hawk@...nel.org,
john.fastabend@...il.com,
bjorn@...nel.org,
magnus.karlsson@...el.com,
maciej.fijalkowski@...el.com,
jonathan.lemon@...il.com,
jdamato@...tly.com,
mkarsten@...terloo.ca
Subject: [PATCH net] xsk: Bring back busy polling support
Commit 86e25f40aa1e ("net: napi: Add napi_config") moved napi->napi_id
assignment to a later point in time (napi_hash_add_with_id). This breaks
__xdp_rxq_info_reg which copies napi_id at an earlier time and now
stores 0 napi_id. It also makes sk_mark_napi_id_once_xdp and
__sk_mark_napi_id_once useless because they now work against 0 napi_id.
Since sk_busy_loop requires valid napi_id to busy-poll on, there is no way
to busy-poll AF_XDP sockets anymore.
Bring back the ability to busy-poll on XSK by resolving socket's napi_id
at bind time. This relies on relatively recent netif_queue_set_napi,
but (assume) at this point most popular drivers should have been converted.
This also removes per-tx/rx cycles which used to check and/or set
the napi_id value.
Confirmed by running a busy-polling AF_XDP socket
(github.com/fomichev/xskrtt) on mlx5 and looking at BusyPollRxPackets
from /proc/net/netstat.
Fixes: 86e25f40aa1e ("net: napi: Add napi_config")
Signed-off-by: Stanislav Fomichev <sdf@...ichev.me>
---
include/net/busy_poll.h | 8 --------
include/net/xdp.h | 1 -
include/net/xdp_sock_drv.h | 14 --------------
net/core/xdp.c | 1 -
net/xdp/xsk.c | 14 +++++++++-----
5 files changed, 9 insertions(+), 29 deletions(-)
diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h
index c858270141bc..c39a426ebf52 100644
--- a/include/net/busy_poll.h
+++ b/include/net/busy_poll.h
@@ -174,12 +174,4 @@ static inline void sk_mark_napi_id_once(struct sock *sk,
#endif
}
-static inline void sk_mark_napi_id_once_xdp(struct sock *sk,
- const struct xdp_buff *xdp)
-{
-#ifdef CONFIG_NET_RX_BUSY_POLL
- __sk_mark_napi_id_once(sk, xdp->rxq->napi_id);
-#endif
-}
-
#endif /* _LINUX_NET_BUSY_POLL_H */
diff --git a/include/net/xdp.h b/include/net/xdp.h
index e6770dd40c91..b5b10f2b88e5 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -62,7 +62,6 @@ struct xdp_rxq_info {
u32 queue_index;
u32 reg_state;
struct xdp_mem_info mem;
- unsigned int napi_id;
u32 frag_size;
} ____cacheline_aligned; /* perf critical, avoid false-sharing */
diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h
index 40085afd9160..7a7316d9c0da 100644
--- a/include/net/xdp_sock_drv.h
+++ b/include/net/xdp_sock_drv.h
@@ -59,15 +59,6 @@ static inline void xsk_pool_fill_cb(struct xsk_buff_pool *pool,
xp_fill_cb(pool, desc);
}
-static inline unsigned int xsk_pool_get_napi_id(struct xsk_buff_pool *pool)
-{
-#ifdef CONFIG_NET_RX_BUSY_POLL
- return pool->heads[0].xdp.rxq->napi_id;
-#else
- return 0;
-#endif
-}
-
static inline void xsk_pool_dma_unmap(struct xsk_buff_pool *pool,
unsigned long attrs)
{
@@ -306,11 +297,6 @@ static inline void xsk_pool_fill_cb(struct xsk_buff_pool *pool,
{
}
-static inline unsigned int xsk_pool_get_napi_id(struct xsk_buff_pool *pool)
-{
- return 0;
-}
-
static inline void xsk_pool_dma_unmap(struct xsk_buff_pool *pool,
unsigned long attrs)
{
diff --git a/net/core/xdp.c b/net/core/xdp.c
index bcc5551c6424..2315feed94ef 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -186,7 +186,6 @@ int __xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq,
xdp_rxq_info_init(xdp_rxq);
xdp_rxq->dev = dev;
xdp_rxq->queue_index = queue_index;
- xdp_rxq->napi_id = napi_id;
xdp_rxq->frag_size = frag_size;
xdp_rxq->reg_state = REG_STATE_REGISTERED;
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 3fa70286c846..89d2bef96469 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -322,7 +322,6 @@ static int xsk_rcv_check(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len)
return -ENOSPC;
}
- sk_mark_napi_id_once_xdp(&xs->sk, xdp);
return 0;
}
@@ -908,11 +907,8 @@ static int __xsk_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len
if (unlikely(!xs->tx))
return -ENOBUFS;
- if (sk_can_busy_loop(sk)) {
- if (xs->zc)
- __sk_mark_napi_id_once(sk, xsk_pool_get_napi_id(xs->pool));
+ if (sk_can_busy_loop(sk))
sk_busy_loop(sk, 1); /* only support non-blocking sockets */
- }
if (xs->zc && xsk_no_wakeup(sk))
return 0;
@@ -1298,6 +1294,14 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
xs->queue_id = qid;
xp_add_xsk(xs->pool, xs);
+ if (xs->zc && qid < dev->real_num_rx_queues) {
+ struct netdev_rx_queue *rxq;
+
+ rxq = __netif_get_rx_queue(dev, qid);
+ if (rxq->napi)
+ __sk_mark_napi_id_once(sk, rxq->napi->napi_id);
+ }
+
out_unlock:
if (err) {
dev_put(dev);
--
2.47.1
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