| Message ID | 1501541855-7354-9-git-send-email-sstabellini@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 07/31/2017 06:57 PM, 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 <stefano@aporeto.com> > CC: boris.ostrovsky@oracle.com > CC: jgross@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 f83b910..369acde 100644 > --- a/drivers/xen/pvcalls-front.c > +++ b/drivers/xen/pvcalls-front.c > @@ -29,6 +29,7 @@ > #define PVCALLS_INVALID_ID UINT_MAX > #define PVCALLS_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER > #define PVCALLS_NR_REQ_PER_RING __CONST_RING_SIZE(xen_pvcalls, XEN_PAGE_SIZE) > +#define PVCALLS_FRONT_MAX_SPIN 5000 > > struct pvcalls_bedata { > struct xen_pvcalls_front_ring ring; > @@ -88,6 +89,22 @@ static inline int get_request(struct pvcalls_bedata *bedata, int *req_id) > return 0; > } > > +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); Do you ever look at actual return value except whether it's zero or not? Both here and in the poll patch you look for !=0 and never check for an error. > +} > + > static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id) > { > struct xenbus_device *dev = dev_id; > @@ -325,6 +342,98 @@ 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; This can be done before the barrier. (In fact, this can be done first thing, before cons and prod are read). > + > + 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; You are returning size_t. I actually was going to ask in one of the previous patches whether using int for sizes was correct. Unfortunately I can't remember which struct/function I was looking at ;-( Of course, you are also possibly returning a (negative) error here. > +} > + > +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; 'sent' doesn't need to be initialized. > + 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; IIRC the error value for sk_send_head being zero is inconsistent across patches. > + > + 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_FRONT_MAX_SPIN) > + goto again; > + if (sent < 0) > + tot_sent = sent; What does it mean when an error is detected on the interface? Does it need to be somehow propagated to the caller? -boris > + > + 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 >
On Mon, 14 Aug 2017, Boris Ostrovsky wrote: > On 07/31/2017 06:57 PM, 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 <stefano@aporeto.com> > > CC: boris.ostrovsky@oracle.com > > CC: jgross@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 f83b910..369acde 100644 > > --- a/drivers/xen/pvcalls-front.c > > +++ b/drivers/xen/pvcalls-front.c > > @@ -29,6 +29,7 @@ > > #define PVCALLS_INVALID_ID UINT_MAX > > #define PVCALLS_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER > > #define PVCALLS_NR_REQ_PER_RING __CONST_RING_SIZE(xen_pvcalls, > > XEN_PAGE_SIZE) > > +#define PVCALLS_FRONT_MAX_SPIN 5000 > > struct pvcalls_bedata { > > struct xen_pvcalls_front_ring ring; > > @@ -88,6 +89,22 @@ static inline int get_request(struct pvcalls_bedata > > *bedata, int *req_id) > > return 0; > > } > > +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); > > Do you ever look at actual return value except whether it's zero or not? Both > here and in the poll patch you look for !=0 and never check for an error. No, I can turn the return value into bool. > > +} > > + > > static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id) > > { > > struct xenbus_device *dev = dev_id; > > @@ -325,6 +342,98 @@ 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; > > This can be done before the barrier. (In fact, this can be done first thing, > before cons and prod are read). Good point. > > + > > + 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; > > You are returning size_t. I actually was going to ask in one of the previous > patches whether using int for sizes was correct. Unfortunately I can't > remember which struct/function I was looking at ;-( > > Of course, you are also possibly returning a (negative) error here. You are right, len should not be size_t but ssize_t or int. Especially given that we cannot write more than array_size bytes to the ring. For simplicity, I'll change the type of len to int in __write_ring and add a check on len >= INT_MAX in the caller. > > +} > > + > > +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; > > 'sent' doesn't need to be initialized. OK > > + 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; > > IIRC the error value for sk_send_head being zero is inconsistent across > patches. I'll fix it. > > + > > + 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_FRONT_MAX_SPIN) > > + goto again; > > + if (sent < 0) > > + tot_sent = sent; > > What does it mean when an error is detected on the interface? Does it need to > be somehow propagated to the caller? The error could be a genuine socket error set by the backend, for example ECONNRESET (Connection reset by peer). The error will be returned by __write_ring. By setting tot_sent to sent, we return it to the caller of pvcalls_front_sendmsg. Eventually the userspace application will see an errno = ECONNRESET.
diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c index f83b910..369acde 100644 --- a/drivers/xen/pvcalls-front.c +++ b/drivers/xen/pvcalls-front.c @@ -29,6 +29,7 @@ #define PVCALLS_INVALID_ID UINT_MAX #define PVCALLS_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER #define PVCALLS_NR_REQ_PER_RING __CONST_RING_SIZE(xen_pvcalls, XEN_PAGE_SIZE) +#define PVCALLS_FRONT_MAX_SPIN 5000 struct pvcalls_bedata { struct xen_pvcalls_front_ring ring; @@ -88,6 +89,22 @@ static inline int get_request(struct pvcalls_bedata *bedata, int *req_id) return 0; } +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; @@ -325,6 +342,98 @@ 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_FRONT_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
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 <stefano@aporeto.com> CC: boris.ostrovsky@oracle.com CC: jgross@suse.com --- drivers/xen/pvcalls-front.c | 109 ++++++++++++++++++++++++++++++++++++++++++++ drivers/xen/pvcalls-front.h | 3 ++ 2 files changed, 112 insertions(+)