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xsk: Bring back busy polling support

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Commit 86e25f40aa ("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: 86e25f40aa ("net: napi: Add napi_config")
Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Link: https://patch.msgid.link/20250109003436.2829560-1-sdf@fomichev.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Stanislav Fomichev 2025-01-08 16:34:36 -08:00 committed by Jakub Kicinski
parent f0aa6a37a3
commit 5ef44b3cb4
5 changed files with 9 additions and 29 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

8
include/net/busy_poll.h
View file

@ -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 */

1
include/net/xdp.h
View file

@ -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 */

14
include/net/xdp_sock_drv.h
View file

@ -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)
{

1
net/core/xdp.c
View file

@ -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;

14
net/xdp/xsk.c
View file

@ -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);