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Date: Wed, 2 Dec 2020 16:30:07 +0100 From: Magnus Karlsson <magnus.karlsson@...il.com> To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com> Cc: "Karlsson, Magnus" <magnus.karlsson@...el.com>, Daniel Borkmann <daniel@...earbox.net>, Björn Töpel <bjorn.topel@...el.com>, Jonathan Lemon <jonathan.lemon@...il.com>, "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Alexei Starovoitov <ast@...nel.org>, Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>, Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, KP Singh <kpsingh@...omium.org>, "open list:XDP SOCKETS (AF_XDP)" <netdev@...r.kernel.org>, "open list:XDP SOCKETS (AF_XDP)" <bpf@...r.kernel.org>, open list <linux-kernel@...r.kernel.org> Subject: Re: [PATCH bpf V3 2/2] xsk: change the tx writeable condition On Tue, Dec 1, 2020 at 2:59 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote: > > Modify the tx writeable condition from the queue is not full to the > number of present tx queues is less than the half of the total number > of queues. Because the tx queue not full is a very short time, this will > cause a large number of EPOLLOUT events, and cause a large number of > process wake up. And the Fixes label here should be: Fixes: 35fcde7f8deb ("xsk: support for Tx") > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com> > Acked-by: Magnus Karlsson <magnus.karlsson@...el.com> > --- > net/xdp/xsk.c | 16 +++++++++++++--- > net/xdp/xsk_queue.h | 6 ++++++ > 2 files changed, 19 insertions(+), 3 deletions(-) > > diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c > index 9bbfd8a..6250447 100644 > --- a/net/xdp/xsk.c > +++ b/net/xdp/xsk.c > @@ -211,6 +211,14 @@ static int __xsk_rcv(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len, > return 0; > } > > +static bool xsk_tx_writeable(struct xdp_sock *xs) > +{ > + if (xskq_cons_present_entries(xs->tx) > xs->tx->nentries / 2) > + return false; > + > + return true; > +} > + > static bool xsk_is_bound(struct xdp_sock *xs) > { > if (READ_ONCE(xs->state) == XSK_BOUND) { > @@ -296,7 +304,8 @@ void xsk_tx_release(struct xsk_buff_pool *pool) > rcu_read_lock(); > list_for_each_entry_rcu(xs, &pool->xsk_tx_list, tx_list) { > __xskq_cons_release(xs->tx); > - xs->sk.sk_write_space(&xs->sk); > + if (xsk_tx_writeable(xs)) > + xs->sk.sk_write_space(&xs->sk); > } > rcu_read_unlock(); > } > @@ -436,7 +445,8 @@ static int xsk_generic_xmit(struct sock *sk) > > out: > if (sent_frame) > - sk->sk_write_space(sk); > + if (xsk_tx_writeable(xs)) > + sk->sk_write_space(sk); > > mutex_unlock(&xs->mutex); > return err; > @@ -493,7 +503,7 @@ static __poll_t xsk_poll(struct file *file, struct socket *sock, > > if (xs->rx && !xskq_prod_is_empty(xs->rx)) > mask |= EPOLLIN | EPOLLRDNORM; > - if (xs->tx && !xskq_cons_is_full(xs->tx)) > + if (xs->tx && xsk_tx_writeable(xs)) > mask |= EPOLLOUT | EPOLLWRNORM; > > return mask; > diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h > index cdb9cf3..9e71b9f 100644 > --- a/net/xdp/xsk_queue.h > +++ b/net/xdp/xsk_queue.h > @@ -264,6 +264,12 @@ static inline bool xskq_cons_is_full(struct xsk_queue *q) > q->nentries; > } > > +static inline u32 xskq_cons_present_entries(struct xsk_queue *q) > +{ > + /* No barriers needed since data is not accessed */ > + return READ_ONCE(q->ring->producer) - READ_ONCE(q->ring->consumer); > +} > + > /* Functions for producers */ > > static inline bool xskq_prod_is_full(struct xsk_queue *q) > -- > 1.8.3.1 >
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