Send data to an active socket by copying data to the "out" ring. Take the active socket out_mutex so that only one function can access the ring at any given time.
If not enough room is available on the ring, rather than returning immediately or sleep-waiting, spin for up to 5000 cycles. This small optimization turns out to improve performance significantly. Signed-off-by: Stefano Stabellini <stef...@aporeto.com> CC: boris.ostrov...@oracle.com CC: jgr...@suse.com --- drivers/xen/pvcalls-front.c | 109 ++++++++++++++++++++++++++++++++++++++++++++ drivers/xen/pvcalls-front.h | 3 ++ 2 files changed, 112 insertions(+) diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c index f3a04a2..bf29f40 100644 --- a/drivers/xen/pvcalls-front.c +++ b/drivers/xen/pvcalls-front.c @@ -27,6 +27,7 @@ #define PVCALLS_INVALID_ID (UINT_MAX) #define RING_ORDER XENBUS_MAX_RING_GRANT_ORDER #define PVCALLS_NR_REQ_PER_RING __CONST_RING_SIZE(xen_pvcalls, XEN_PAGE_SIZE) +#define PVCALLS_FRON_MAX_SPIN 5000 struct pvcalls_bedata { struct xen_pvcalls_front_ring ring; @@ -77,6 +78,22 @@ struct sock_mapping { }; }; +static int pvcalls_front_write_todo(struct sock_mapping *map) +{ + struct pvcalls_data_intf *intf = map->active.ring; + RING_IDX cons, prod, size = XEN_FLEX_RING_SIZE(intf->ring_order); + int32_t error; + + cons = intf->out_cons; + prod = intf->out_prod; + error = intf->out_error; + if (error == -ENOTCONN) + return 0; + if (error != 0) + return error; + return size - pvcalls_queued(prod, cons, size); +} + static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id) { struct xenbus_device *dev = dev_id; @@ -304,6 +321,98 @@ int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr, return ret; } +static int __write_ring(struct pvcalls_data_intf *intf, + struct pvcalls_data *data, + struct iov_iter *msg_iter, + size_t len) +{ + RING_IDX cons, prod, size, masked_prod, masked_cons; + RING_IDX array_size = XEN_FLEX_RING_SIZE(intf->ring_order); + int32_t error; + + cons = intf->out_cons; + prod = intf->out_prod; + error = intf->out_error; + /* read indexes before continuing */ + virt_mb(); + + if (error < 0) + return error; + + size = pvcalls_queued(prod, cons, array_size); + if (size >= array_size) + return 0; + if (len > array_size - size) + len = array_size - size; + + masked_prod = pvcalls_mask(prod, array_size); + masked_cons = pvcalls_mask(cons, array_size); + + if (masked_prod < masked_cons) { + copy_from_iter(data->out + masked_prod, len, msg_iter); + } else { + if (len > array_size - masked_prod) { + copy_from_iter(data->out + masked_prod, + array_size - masked_prod, msg_iter); + copy_from_iter(data->out, + len - (array_size - masked_prod), + msg_iter); + } else { + copy_from_iter(data->out + masked_prod, len, msg_iter); + } + } + /* write to ring before updating pointer */ + virt_wmb(); + intf->out_prod += len; + + return len; +} + +int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg, + size_t len) +{ + struct pvcalls_bedata *bedata; + struct sock_mapping *map; + int sent = 0, tot_sent = 0; + int count = 0, flags; + + if (!pvcalls_front_dev) + return -ENOTCONN; + bedata = dev_get_drvdata(&pvcalls_front_dev->dev); + + map = (struct sock_mapping *) READ_ONCE(sock->sk->sk_send_head); + if (!map) + return -ENOTSOCK; + + flags = msg->msg_flags; + if (flags & (MSG_CONFIRM|MSG_DONTROUTE|MSG_EOR|MSG_OOB)) + return -EOPNOTSUPP; + + mutex_lock(&map->active.out_mutex); + if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) { + mutex_unlock(&map->active.out_mutex); + return -EAGAIN; + } + +again: + count++; + sent = __write_ring(map->active.ring, + &map->active.data, &msg->msg_iter, + len); + if (sent > 0) { + len -= sent; + tot_sent += sent; + notify_remote_via_irq(map->active.irq); + } + if (sent >= 0 && len > 0 && count < PVCALLS_FRON_MAX_SPIN) + goto again; + if (sent < 0) + tot_sent = sent; + + mutex_unlock(&map->active.out_mutex); + return tot_sent; +} + int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len) { struct pvcalls_bedata *bedata; diff --git a/drivers/xen/pvcalls-front.h b/drivers/xen/pvcalls-front.h index ab4f1da..d937c24 100644 --- a/drivers/xen/pvcalls-front.h +++ b/drivers/xen/pvcalls-front.h @@ -13,5 +13,8 @@ int pvcalls_front_bind(struct socket *sock, int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags); +int pvcalls_front_sendmsg(struct socket *sock, + struct msghdr *msg, + size_t len); #endif -- 1.9.1