Patchwork [v2,1/3] net: asynchronous send/receive infrastructure for net/socket.c

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Submitter Stefan Hajnoczi
Date Aug. 21, 2012, 3:52 p.m.
Message ID <1345564351-14693-2-git-send-email-stefanha@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/179083/
State New
Headers show

Comments

Stefan Hajnoczi - Aug. 21, 2012, 3:52 p.m.
The net/socket.c net client is not truly asynchronous.  This patch
borrows the qemu_set_fd_handler2() code from net/tap.c as the basis for
proper asynchronous send/receive.

Only read packets from the socket when the peer is able to receive.
This avoids needless queuing.

Later patches implement asynchronous send.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 net/socket.c |   58 ++++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 52 insertions(+), 6 deletions(-)
ronniesahlberg@gmail.com - Aug. 21, 2012, 4:39 p.m.
In
net_socket_update_fd_handler()

shouldnt you call qemu_notify_event() if any of the handlers have
changed from NULL to non-NULL ?
or else it might take a while before the change takes effect.


regards
ronnie sahlberg

On Wed, Aug 22, 2012 at 1:52 AM, Stefan Hajnoczi
<stefanha@linux.vnet.ibm.com> wrote:
> The net/socket.c net client is not truly asynchronous.  This patch
> borrows the qemu_set_fd_handler2() code from net/tap.c as the basis for
> proper asynchronous send/receive.
>
> Only read packets from the socket when the peer is able to receive.
> This avoids needless queuing.
>
> Later patches implement asynchronous send.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> ---
>  net/socket.c |   58 ++++++++++++++++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 52 insertions(+), 6 deletions(-)
>
> diff --git a/net/socket.c b/net/socket.c
> index c172c24..54e32f0 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -42,9 +42,51 @@ typedef struct NetSocketState {
>      unsigned int packet_len;
>      uint8_t buf[4096];
>      struct sockaddr_in dgram_dst; /* contains inet host and port destination iff connectionless (SOCK_DGRAM) */
> +    IOHandler *send_fn;           /* differs between SOCK_STREAM/SOCK_DGRAM */
> +    bool read_poll;               /* waiting to receive data? */
> +    bool write_poll;              /* waiting to transmit data? */
>  } NetSocketState;
>
>  static void net_socket_accept(void *opaque);
> +static void net_socket_writable(void *opaque);
> +
> +/* Only read packets from socket when peer can receive them */
> +static int net_socket_can_send(void *opaque)
> +{
> +    NetSocketState *s = opaque;
> +
> +    return qemu_can_send_packet(&s->nc);
> +}
> +
> +static void net_socket_update_fd_handler(NetSocketState *s)
> +{
> +    qemu_set_fd_handler2(s->fd,
> +                         s->read_poll  ? net_socket_can_send : NULL,
> +                         s->read_poll  ? s->send_fn : NULL,
> +                         s->write_poll ? net_socket_writable : NULL,
> +                         s);
> +}
> +
> +static void net_socket_read_poll(NetSocketState *s, bool enable)
> +{
> +    s->read_poll = enable;
> +    net_socket_update_fd_handler(s);
> +}
> +
> +static void net_socket_write_poll(NetSocketState *s, bool enable)
> +{
> +    s->write_poll = enable;
> +    net_socket_update_fd_handler(s);
> +}
> +
> +static void net_socket_writable(void *opaque)
> +{
> +    NetSocketState *s = opaque;
> +
> +    net_socket_write_poll(s, false);
> +
> +    qemu_flush_queued_packets(&s->nc);
> +}
>
>  /* XXX: we consider we can send the whole packet without blocking */
>  static ssize_t net_socket_receive(NetClientState *nc, const uint8_t *buf, size_t size)
> @@ -81,7 +123,8 @@ static void net_socket_send(void *opaque)
>      } else if (size == 0) {
>          /* end of connection */
>      eoc:
> -        qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
> +        net_socket_read_poll(s, false);
> +        net_socket_write_poll(s, false);
>          if (s->listen_fd != -1) {
>              qemu_set_fd_handler(s->listen_fd, net_socket_accept, NULL, s);
>          }
> @@ -152,7 +195,8 @@ static void net_socket_send_dgram(void *opaque)
>          return;
>      if (size == 0) {
>          /* end of connection */
> -        qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
> +        net_socket_read_poll(s, false);
> +        net_socket_write_poll(s, false);
>          return;
>      }
>      qemu_send_packet(&s->nc, s->buf, size);
> @@ -243,7 +287,8 @@ static void net_socket_cleanup(NetClientState *nc)
>  {
>      NetSocketState *s = DO_UPCAST(NetSocketState, nc, nc);
>      if (s->fd != -1) {
> -        qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
> +        net_socket_read_poll(s, false);
> +        net_socket_write_poll(s, false);
>          close(s->fd);
>          s->fd = -1;
>      }
> @@ -314,8 +359,8 @@ static NetSocketState *net_socket_fd_init_dgram(NetClientState *peer,
>
>      s->fd = fd;
>      s->listen_fd = -1;
> -
> -    qemu_set_fd_handler(s->fd, net_socket_send_dgram, NULL, s);
> +    s->send_fn = net_socket_send_dgram;
> +    net_socket_read_poll(s, true);
>
>      /* mcast: save bound address as dst */
>      if (is_connected) {
> @@ -332,7 +377,8 @@ err:
>  static void net_socket_connect(void *opaque)
>  {
>      NetSocketState *s = opaque;
> -    qemu_set_fd_handler(s->fd, net_socket_send, NULL, s);
> +    s->send_fn = net_socket_send;
> +    net_socket_read_poll(s, true);
>  }
>
>  static NetClientInfo net_socket_info = {
> --
> 1.7.10.4
>
>
Paolo Bonzini - Aug. 21, 2012, 6:54 p.m.
Il 21/08/2012 18:39, ronnie sahlberg ha scritto:
> In
> net_socket_update_fd_handler()
> 
> shouldnt you call qemu_notify_event() if any of the handlers have
> changed from NULL to non-NULL ?
> or else it might take a while before the change takes effect.

Why haven't we applied yet the patch to do that unconditionally?

http://permalink.gmane.org/gmane.comp.emulators.qemu/162828

Paolo
Anthony Liguori - Aug. 21, 2012, 7:06 p.m.
Paolo Bonzini <pbonzini@redhat.com> writes:

> Il 21/08/2012 18:39, ronnie sahlberg ha scritto:
>> In
>> net_socket_update_fd_handler()
>> 
>> shouldnt you call qemu_notify_event() if any of the handlers have
>> changed from NULL to non-NULL ?
>> or else it might take a while before the change takes effect.
>
> Why haven't we applied yet the patch to do that unconditionally?
>
> http://permalink.gmane.org/gmane.comp.emulators.qemu/162828

Can you ping the actual patch... Gmane seems to be down right now.

Regards,

Anthony Liguori

>
> Paolo
Stefan Hajnoczi - Aug. 22, 2012, 9:24 a.m.
On Tue, Aug 21, 2012 at 5:39 PM, ronnie sahlberg
<ronniesahlberg@gmail.com> wrote:
> In
> net_socket_update_fd_handler()
>
> shouldnt you call qemu_notify_event() if any of the handlers have
> changed from NULL to non-NULL ?
> or else it might take a while before the change takes effect.

In this case it's not necessary:

net_socket_send()/net_socket_send_dgram()/net_socket_writable() are
called as fd handlers and therefore we know the event loop isn't stuck
in select(2).

Stefan
Paolo Bonzini - Aug. 22, 2012, 9:07 p.m.
Il 21/08/2012 21:06, Anthony Liguori ha scritto:
> Paolo Bonzini <pbonzini@redhat.com> writes:
> 
>> Il 21/08/2012 18:39, ronnie sahlberg ha scritto:
>>> In
>>> net_socket_update_fd_handler()
>>>
>>> shouldnt you call qemu_notify_event() if any of the handlers have
>>> changed from NULL to non-NULL ?
>>> or else it might take a while before the change takes effect.
>>
>> Why haven't we applied yet the patch to do that unconditionally?
>>
>> http://permalink.gmane.org/gmane.comp.emulators.qemu/162828
> 
> Can you ping the actual patch... Gmane seems to be down right now.

David Gibson sent it again a few hours ago ("[PATCH] eventfd: making it
thread safe") with my Reviewed-by.

Paolo
Anthony Liguori - Aug. 22, 2012, 9:25 p.m.
Paolo Bonzini <pbonzini@redhat.com> writes:

> Il 21/08/2012 21:06, Anthony Liguori ha scritto:
>> Paolo Bonzini <pbonzini@redhat.com> writes:
>> 
>>> Il 21/08/2012 18:39, ronnie sahlberg ha scritto:
>>>> In
>>>> net_socket_update_fd_handler()
>>>>
>>>> shouldnt you call qemu_notify_event() if any of the handlers have
>>>> changed from NULL to non-NULL ?
>>>> or else it might take a while before the change takes effect.
>>>
>>> Why haven't we applied yet the patch to do that unconditionally?
>>>
>>> http://permalink.gmane.org/gmane.comp.emulators.qemu/162828
>> 
>> Can you ping the actual patch... Gmane seems to be down right now.
>
> David Gibson sent it again a few hours ago ("[PATCH] eventfd: making it
> thread safe") with my Reviewed-by.

Yup, I've applied it.  Thanks.

Regards,

Anthony Liguori

>
> Paolo

Patch

diff --git a/net/socket.c b/net/socket.c
index c172c24..54e32f0 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -42,9 +42,51 @@  typedef struct NetSocketState {
     unsigned int packet_len;
     uint8_t buf[4096];
     struct sockaddr_in dgram_dst; /* contains inet host and port destination iff connectionless (SOCK_DGRAM) */
+    IOHandler *send_fn;           /* differs between SOCK_STREAM/SOCK_DGRAM */
+    bool read_poll;               /* waiting to receive data? */
+    bool write_poll;              /* waiting to transmit data? */
 } NetSocketState;
 
 static void net_socket_accept(void *opaque);
+static void net_socket_writable(void *opaque);
+
+/* Only read packets from socket when peer can receive them */
+static int net_socket_can_send(void *opaque)
+{
+    NetSocketState *s = opaque;
+
+    return qemu_can_send_packet(&s->nc);
+}
+
+static void net_socket_update_fd_handler(NetSocketState *s)
+{
+    qemu_set_fd_handler2(s->fd,
+                         s->read_poll  ? net_socket_can_send : NULL,
+                         s->read_poll  ? s->send_fn : NULL,
+                         s->write_poll ? net_socket_writable : NULL,
+                         s);
+}
+
+static void net_socket_read_poll(NetSocketState *s, bool enable)
+{
+    s->read_poll = enable;
+    net_socket_update_fd_handler(s);
+}
+
+static void net_socket_write_poll(NetSocketState *s, bool enable)
+{
+    s->write_poll = enable;
+    net_socket_update_fd_handler(s);
+}
+
+static void net_socket_writable(void *opaque)
+{
+    NetSocketState *s = opaque;
+
+    net_socket_write_poll(s, false);
+
+    qemu_flush_queued_packets(&s->nc);
+}
 
 /* XXX: we consider we can send the whole packet without blocking */
 static ssize_t net_socket_receive(NetClientState *nc, const uint8_t *buf, size_t size)
@@ -81,7 +123,8 @@  static void net_socket_send(void *opaque)
     } else if (size == 0) {
         /* end of connection */
     eoc:
-        qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
+        net_socket_read_poll(s, false);
+        net_socket_write_poll(s, false);
         if (s->listen_fd != -1) {
             qemu_set_fd_handler(s->listen_fd, net_socket_accept, NULL, s);
         }
@@ -152,7 +195,8 @@  static void net_socket_send_dgram(void *opaque)
         return;
     if (size == 0) {
         /* end of connection */
-        qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
+        net_socket_read_poll(s, false);
+        net_socket_write_poll(s, false);
         return;
     }
     qemu_send_packet(&s->nc, s->buf, size);
@@ -243,7 +287,8 @@  static void net_socket_cleanup(NetClientState *nc)
 {
     NetSocketState *s = DO_UPCAST(NetSocketState, nc, nc);
     if (s->fd != -1) {
-        qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
+        net_socket_read_poll(s, false);
+        net_socket_write_poll(s, false);
         close(s->fd);
         s->fd = -1;
     }
@@ -314,8 +359,8 @@  static NetSocketState *net_socket_fd_init_dgram(NetClientState *peer,
 
     s->fd = fd;
     s->listen_fd = -1;
-
-    qemu_set_fd_handler(s->fd, net_socket_send_dgram, NULL, s);
+    s->send_fn = net_socket_send_dgram;
+    net_socket_read_poll(s, true);
 
     /* mcast: save bound address as dst */
     if (is_connected) {
@@ -332,7 +377,8 @@  err:
 static void net_socket_connect(void *opaque)
 {
     NetSocketState *s = opaque;
-    qemu_set_fd_handler(s->fd, net_socket_send, NULL, s);
+    s->send_fn = net_socket_send;
+    net_socket_read_poll(s, true);
 }
 
 static NetClientInfo net_socket_info = {