| Message ID | 1505516440-11111-9-git-send-email-sstabellini@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
> +static bool 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(PVCALLS_RING_ORDER); > + int32_t error; > + > + cons = intf->out_cons; > + prod = intf->out_prod; > + error = intf->out_error; > + if (error == -ENOTCONN) > + return false; > + if (error != 0) > + return true; Just like below, error processing can be moved up. > + 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; > @@ -363,6 +380,108 @@ 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, > + int len) > +{ > + RING_IDX cons, prod, size, masked_prod, masked_cons; > + RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER); > + int32_t error; > + > + error = intf->out_error; > + if (error < 0) > + return error; > + cons = intf->out_cons; > + prod = intf->out_prod; > + /* read indexes before continuing */ > + virt_mb(); > + > + size = pvcalls_queued(prod, cons, array_size); > + if (size >= array_size) > + return 0; Is it possible to have size > array_size? > + 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; I know that you said you'd be changing len's type to int but now that I am looking at it I wonder whether you could pass len as a 'size_t *' and have this routine return error code (i.e. <=0). OTOH, we'd be mixing up types again since RING_IDX is an unsigned int. So I'll leave it to you (or anyone else reviewing this) to decide which way is better. > +} > + > +int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg, > + size_t len) Also, the signature here looks suspicious --- you are trying to send 'size_t len' bytes but returning an int, which is how many bytes you've actually sent. Right? -boris
On Fri, 22 Sep 2017, Boris Ostrovsky wrote: > > +static bool 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(PVCALLS_RING_ORDER); > > + int32_t error; > > + > > + cons = intf->out_cons; > > + prod = intf->out_prod; > > + error = intf->out_error; > > + if (error == -ENOTCONN) > > + return false; > > + if (error != 0) > > + return true; > > Just like below, error processing can be moved up. OK > > + 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; > > @@ -363,6 +380,108 @@ 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, > > + int len) > > +{ > > + RING_IDX cons, prod, size, masked_prod, masked_cons; > > + RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER); > > + int32_t error; > > + > > + error = intf->out_error; > > + if (error < 0) > > + return error; > > + cons = intf->out_cons; > > + prod = intf->out_prod; > > + /* read indexes before continuing */ > > + virt_mb(); > > + > > + size = pvcalls_queued(prod, cons, array_size); > > + if (size >= array_size) > > + return 0; > > > Is it possible to have size > array_size? Yes, if somebody makes a mistake in writing to prod. Of course, it is not valid. I guess I could return error instead of 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; > > > I know that you said you'd be changing len's type to int but now that I > am looking at it I wonder whether you could pass len as a 'size_t *' and > have this routine return error code (i.e. <=0). > > OTOH, we'd be mixing up types again since RING_IDX is an unsigned int. > > So I'll leave it to you (or anyone else reviewing this) to decide which > way is better. see below > > +} > > + > > +int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg, > > + size_t len) > > Also, the signature here looks suspicious --- you are trying to send > 'size_t len' bytes but returning an int, which is how many bytes you've > actually sent. Right? Yes, but it is OK because it is limited by the size of the array which is far smaller than INT_MAX (the array size is 262144). This is also why I would just keep len as int.
diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c index 414eafd..2907e85 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; @@ -101,6 +102,22 @@ static inline int get_request(struct pvcalls_bedata *bedata, int *req_id) return 0; } +static bool 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(PVCALLS_RING_ORDER); + int32_t error; + + cons = intf->out_cons; + prod = intf->out_prod; + error = intf->out_error; + if (error == -ENOTCONN) + return false; + if (error != 0) + return true; + 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; @@ -363,6 +380,108 @@ 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, + int len) +{ + RING_IDX cons, prod, size, masked_prod, masked_cons; + RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER); + int32_t error; + + error = intf->out_error; + if (error < 0) + return error; + cons = intf->out_cons; + prod = intf->out_prod; + /* read indexes before continuing */ + virt_mb(); + + 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, tot_sent = 0; + int count = 0, flags; + + pvcalls_enter; + if (!pvcalls_front_dev) { + pvcalls_exit; + return -ENOTCONN; + } + bedata = dev_get_drvdata(&pvcalls_front_dev->dev); + + map = (struct sock_mapping *) sock->sk->sk_send_head; + if (!map) { + pvcalls_exit; + return -ENOTSOCK; + } + + flags = msg->msg_flags; + if (flags & (MSG_CONFIRM|MSG_DONTROUTE|MSG_EOR|MSG_OOB)) { + pvcalls_exit; + return -EOPNOTSUPP; + } + + mutex_lock(&map->active.out_mutex); + if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) { + mutex_unlock(&map->active.out_mutex); + pvcalls_exit; + return -EAGAIN; + } + if (len > INT_MAX) + len = INT_MAX; + +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); + pvcalls_exit; + 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 | 119 ++++++++++++++++++++++++++++++++++++++++++++ drivers/xen/pvcalls-front.h | 3 ++ 2 files changed, 122 insertions(+)