Message ID | 1501541855-7354-10-git-send-email-sstabellini@kernel.org (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
On 07/31/2017 06:57 PM, Stefano Stabellini wrote: > Implement recvmsg by copying data from the "in" ring. If not enough data > is available and the recvmsg call is blocking, then wait on the > inflight_conn_req waitqueue. Take the active socket in_mutex so that > only one function can access the ring at any given time. > > If no data 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 and latency significantly. > > Signed-off-by: Stefano Stabellini <stefano@aporeto.com> > CC: boris.ostrovsky@oracle.com > CC: jgross@suse.com > --- > drivers/xen/pvcalls-front.c | 102 ++++++++++++++++++++++++++++++++++++++++++++ > drivers/xen/pvcalls-front.h | 4 ++ > 2 files changed, 106 insertions(+) > > diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c > index 369acde..635a83a 100644 > --- a/drivers/xen/pvcalls-front.c > +++ b/drivers/xen/pvcalls-front.c > @@ -105,6 +105,20 @@ static int pvcalls_front_write_todo(struct sock_mapping *map) > return size - pvcalls_queued(prod, cons, size); > } > > +static bool pvcalls_front_read_todo(struct sock_mapping *map) > +{ > + struct pvcalls_data_intf *intf = map->active.ring; > + RING_IDX cons, prod; > + int32_t error; > + > + cons = intf->in_cons; > + prod = intf->in_prod; > + error = intf->in_error; > + return (error != 0 || > + pvcalls_queued(prod, cons, > + XEN_FLEX_RING_SIZE(intf->ring_order)) != 0); > +} > + > static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id) > { > struct xenbus_device *dev = dev_id; > @@ -434,6 +448,94 @@ int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg, > return tot_sent; > } > > +static int __read_ring(struct pvcalls_data_intf *intf, > + struct pvcalls_data *data, > + struct iov_iter *msg_iter, > + size_t len, int flags) > +{ > + 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->in_cons; > + prod = intf->in_prod; > + error = intf->in_error; > + /* get pointers before reading from the ring */ > + virt_rmb(); > + if (error < 0) > + return error; > + > + size = pvcalls_queued(prod, cons, array_size); > + masked_prod = pvcalls_mask(prod, array_size); > + masked_cons = pvcalls_mask(cons, array_size); > + > + if (size == 0) > + return 0; > + > + if (len > size) > + len = size; > + > + if (masked_prod > masked_cons) { > + copy_to_iter(data->in + masked_cons, len, msg_iter); > + } else { > + if (len > (array_size - masked_cons)) { > + copy_to_iter(data->in + masked_cons, > + array_size - masked_cons, msg_iter); > + copy_to_iter(data->in, > + len - (array_size - masked_cons), > + msg_iter); > + } else { > + copy_to_iter(data->in + masked_cons, len, msg_iter); > + } > + } > + /* read data from the ring before increasing the index */ > + virt_mb(); > + if (!(flags & MSG_PEEK)) > + intf->in_cons += len; > + > + return len; > +} > + > +int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, > + int flags) > +{ > + struct pvcalls_bedata *bedata; > + int ret = -EAGAIN; Not necessary to initialize. > + struct sock_mapping *map; > + > + 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; > + > + if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC)) > + return -EOPNOTSUPP; > + > + mutex_lock(&map->active.in_mutex); > + if (len > XEN_FLEX_RING_SIZE(map->active.ring->ring_order)) > + len = XEN_FLEX_RING_SIZE(map->active.ring->ring_order); > + > + while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) { > + wait_event_interruptible(map->active.inflight_conn_req, > + pvcalls_front_read_todo(map)); > + } > + ret = __read_ring(map->active.ring, &map->active.data, > + &msg->msg_iter, len, flags); > + > + if (ret > 0) > + notify_remote_via_irq(map->active.irq); > + if (ret == 0) > + ret = -EAGAIN; > + if (ret == -ENOTCONN) > + ret = 0; > + > + mutex_unlock(&map->active.in_mutex); > + return ret; Are errors converted by the caller? (I am asking because recvmsg can only return -1 for errors) -boris > +} > + > 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 d937c24..de24041 100644 > --- a/drivers/xen/pvcalls-front.h > +++ b/drivers/xen/pvcalls-front.h > @@ -16,5 +16,9 @@ int pvcalls_front_accept(struct socket *sock, > int pvcalls_front_sendmsg(struct socket *sock, > struct msghdr *msg, > size_t len); > +int pvcalls_front_recvmsg(struct socket *sock, > + struct msghdr *msg, > + size_t len, > + int flags); > > #endif >
On Mon, 14 Aug 2017, Boris Ostrovsky wrote: > On 07/31/2017 06:57 PM, Stefano Stabellini wrote: > > Implement recvmsg by copying data from the "in" ring. If not enough data > > is available and the recvmsg call is blocking, then wait on the > > inflight_conn_req waitqueue. Take the active socket in_mutex so that > > only one function can access the ring at any given time. > > > > If no data 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 and latency significantly. > > > > Signed-off-by: Stefano Stabellini <stefano@aporeto.com> > > CC: boris.ostrovsky@oracle.com > > CC: jgross@suse.com > > --- > > drivers/xen/pvcalls-front.c | 102 > > ++++++++++++++++++++++++++++++++++++++++++++ > > drivers/xen/pvcalls-front.h | 4 ++ > > 2 files changed, 106 insertions(+) > > > > diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c > > index 369acde..635a83a 100644 > > --- a/drivers/xen/pvcalls-front.c > > +++ b/drivers/xen/pvcalls-front.c > > @@ -105,6 +105,20 @@ static int pvcalls_front_write_todo(struct sock_mapping > > *map) > > return size - pvcalls_queued(prod, cons, size); > > } > > +static bool pvcalls_front_read_todo(struct sock_mapping *map) > > +{ > > + struct pvcalls_data_intf *intf = map->active.ring; > > + RING_IDX cons, prod; > > + int32_t error; > > + > > + cons = intf->in_cons; > > + prod = intf->in_prod; > > + error = intf->in_error; > > + return (error != 0 || > > + pvcalls_queued(prod, cons, > > + XEN_FLEX_RING_SIZE(intf->ring_order)) != 0); > > +} > > + > > static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id) > > { > > struct xenbus_device *dev = dev_id; > > @@ -434,6 +448,94 @@ int pvcalls_front_sendmsg(struct socket *sock, struct > > msghdr *msg, > > return tot_sent; > > } > > +static int __read_ring(struct pvcalls_data_intf *intf, > > + struct pvcalls_data *data, > > + struct iov_iter *msg_iter, > > + size_t len, int flags) > > +{ > > + 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->in_cons; > > + prod = intf->in_prod; > > + error = intf->in_error; > > + /* get pointers before reading from the ring */ > > + virt_rmb(); > > + if (error < 0) > > + return error; > > + > > + size = pvcalls_queued(prod, cons, array_size); > > + masked_prod = pvcalls_mask(prod, array_size); > > + masked_cons = pvcalls_mask(cons, array_size); > > + > > + if (size == 0) > > + return 0; > > + > > + if (len > size) > > + len = size; > > + > > + if (masked_prod > masked_cons) { > > + copy_to_iter(data->in + masked_cons, len, msg_iter); > > + } else { > > + if (len > (array_size - masked_cons)) { > > + copy_to_iter(data->in + masked_cons, > > + array_size - masked_cons, msg_iter); > > + copy_to_iter(data->in, > > + len - (array_size - masked_cons), > > + msg_iter); > > + } else { > > + copy_to_iter(data->in + masked_cons, len, msg_iter); > > + } > > + } > > + /* read data from the ring before increasing the index */ > > + virt_mb(); > > + if (!(flags & MSG_PEEK)) > > + intf->in_cons += len; > > + > > + return len; > > +} > > + > > +int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t > > len, > > + int flags) > > +{ > > + struct pvcalls_bedata *bedata; > > + int ret = -EAGAIN; > > Not necessary to initialize. Yes, you are right. > > + struct sock_mapping *map; > > + > > + 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; > > + > > + if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC)) > > + return -EOPNOTSUPP; > > + > > + mutex_lock(&map->active.in_mutex); > > + if (len > XEN_FLEX_RING_SIZE(map->active.ring->ring_order)) > > + len = XEN_FLEX_RING_SIZE(map->active.ring->ring_order); > > + > > + while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) { > > + wait_event_interruptible(map->active.inflight_conn_req, > > + pvcalls_front_read_todo(map)); > > + } > > + ret = __read_ring(map->active.ring, &map->active.data, > > + &msg->msg_iter, len, flags); > > + > > + if (ret > 0) > > + notify_remote_via_irq(map->active.irq); > > + if (ret == 0) > > + ret = -EAGAIN; > > + if (ret == -ENOTCONN) > > + ret = 0; > > + > > + mutex_unlock(&map->active.in_mutex); > > + return ret; > > Are errors converted by the caller? (I am asking because recvmsg can only > return -1 for errors) Yes, the caller will set errno appropriately. > > +} > > + > > 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 d937c24..de24041 100644 > > --- a/drivers/xen/pvcalls-front.h > > +++ b/drivers/xen/pvcalls-front.h > > @@ -16,5 +16,9 @@ int pvcalls_front_accept(struct socket *sock, > > int pvcalls_front_sendmsg(struct socket *sock, > > struct msghdr *msg, > > size_t len); > > +int pvcalls_front_recvmsg(struct socket *sock, > > + struct msghdr *msg, > > + size_t len, > > + int flags); > > #endif > > >
diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c index 369acde..635a83a 100644 --- a/drivers/xen/pvcalls-front.c +++ b/drivers/xen/pvcalls-front.c @@ -105,6 +105,20 @@ static int pvcalls_front_write_todo(struct sock_mapping *map) return size - pvcalls_queued(prod, cons, size); } +static bool pvcalls_front_read_todo(struct sock_mapping *map) +{ + struct pvcalls_data_intf *intf = map->active.ring; + RING_IDX cons, prod; + int32_t error; + + cons = intf->in_cons; + prod = intf->in_prod; + error = intf->in_error; + return (error != 0 || + pvcalls_queued(prod, cons, + XEN_FLEX_RING_SIZE(intf->ring_order)) != 0); +} + static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id) { struct xenbus_device *dev = dev_id; @@ -434,6 +448,94 @@ int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg, return tot_sent; } +static int __read_ring(struct pvcalls_data_intf *intf, + struct pvcalls_data *data, + struct iov_iter *msg_iter, + size_t len, int flags) +{ + 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->in_cons; + prod = intf->in_prod; + error = intf->in_error; + /* get pointers before reading from the ring */ + virt_rmb(); + if (error < 0) + return error; + + size = pvcalls_queued(prod, cons, array_size); + masked_prod = pvcalls_mask(prod, array_size); + masked_cons = pvcalls_mask(cons, array_size); + + if (size == 0) + return 0; + + if (len > size) + len = size; + + if (masked_prod > masked_cons) { + copy_to_iter(data->in + masked_cons, len, msg_iter); + } else { + if (len > (array_size - masked_cons)) { + copy_to_iter(data->in + masked_cons, + array_size - masked_cons, msg_iter); + copy_to_iter(data->in, + len - (array_size - masked_cons), + msg_iter); + } else { + copy_to_iter(data->in + masked_cons, len, msg_iter); + } + } + /* read data from the ring before increasing the index */ + virt_mb(); + if (!(flags & MSG_PEEK)) + intf->in_cons += len; + + return len; +} + +int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, + int flags) +{ + struct pvcalls_bedata *bedata; + int ret = -EAGAIN; + struct sock_mapping *map; + + 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; + + if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC)) + return -EOPNOTSUPP; + + mutex_lock(&map->active.in_mutex); + if (len > XEN_FLEX_RING_SIZE(map->active.ring->ring_order)) + len = XEN_FLEX_RING_SIZE(map->active.ring->ring_order); + + while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) { + wait_event_interruptible(map->active.inflight_conn_req, + pvcalls_front_read_todo(map)); + } + ret = __read_ring(map->active.ring, &map->active.data, + &msg->msg_iter, len, flags); + + if (ret > 0) + notify_remote_via_irq(map->active.irq); + if (ret == 0) + ret = -EAGAIN; + if (ret == -ENOTCONN) + ret = 0; + + mutex_unlock(&map->active.in_mutex); + return ret; +} + 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 d937c24..de24041 100644 --- a/drivers/xen/pvcalls-front.h +++ b/drivers/xen/pvcalls-front.h @@ -16,5 +16,9 @@ int pvcalls_front_accept(struct socket *sock, int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg, size_t len); +int pvcalls_front_recvmsg(struct socket *sock, + struct msghdr *msg, + size_t len, + int flags); #endif
Implement recvmsg by copying data from the "in" ring. If not enough data is available and the recvmsg call is blocking, then wait on the inflight_conn_req waitqueue. Take the active socket in_mutex so that only one function can access the ring at any given time. If no data 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 and latency significantly. Signed-off-by: Stefano Stabellini <stefano@aporeto.com> CC: boris.ostrovsky@oracle.com CC: jgross@suse.com --- drivers/xen/pvcalls-front.c | 102 ++++++++++++++++++++++++++++++++++++++++++++ drivers/xen/pvcalls-front.h | 4 ++ 2 files changed, 106 insertions(+)