On Mon, 24 Jul 2017, Juergen Gross wrote: > On 22/07/17 02:11, Stefano Stabellini wrote: > > 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 > > Any reason not to name it PVCALLS_FRONT_MAX_SPIN? I first thought you > meant FROM instead.
Clearly a typo :-) I'll fix it. > > > > > 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 > > >