Re: [Qemu-devel] Proposed patch: huge RX speedup for hw/e1000.c

Re: [Qemu-devel] Proposed patch: huge RX speedup for hw/e1000.c

[Luigi Rizzo]

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Works me. I can now receive at 1.15 Mpps, slightly
faster than my previous patch which generated unnecessary
writes to the signalling socket.

Tested-by: Luigi Rizzo <rizzo@iet.unipi.it>

On Thu, May 31, 2012 at 12:03 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:

> Il 31/05/2012 10:23, Jan Kiszka ha scritto:
> >> > @@ -922,6 +923,7 @@ set_rdt(E1000State *s, int index, uint32_t val)
> >> >  {
> >> >      s->check_rxov = 0;
> >> >      s->mac_reg[index] = val & 0xffff;
> >> > +    qemu_notify_event();
> > This still looks like the wrong tool: Packets that can't be delivered
> > are queued.
>
> Packets that are read from the tap but can't be delivered are queued;
> packets that are left on the tap need qemu_notify_event to be flushed.
>
> > So we need to flush the queue and clear the blocked delivery
> > there. qemu_flush_queued_packets appears more appropriate for this.
>
> Right, and qemu_flush_queued_packets needs to call qemu_notify_event
> which makes the call in virtio-net unnecessary.
>
> Paolo
>
> diff --git a/hw/e1000.c b/hw/e1000.c
> index 4573f13..43d933a 100644
> --- a/hw/e1000.c
> +++ b/hw/e1000.c
> @@ -295,6 +295,7 @@ set_rx_control(E1000State *s, int index, uint32_t val)
>     s->rxbuf_min_shift = ((val / E1000_RCTL_RDMTS_QUAT) & 3) + 1;
>     DBGOUT(RX, "RCTL: %d, mac_reg[RCTL] = 0x%x\n", s->mac_reg[RDT],
>            s->mac_reg[RCTL]);
> +    qemu_flush_queued_packets(&s->nic->nc);
>  }
>
>  static void
> @@ -926,6 +927,9 @@ set_rdt(E1000State *s, int index, uint32_t val)
>  {
>     s->check_rxov = 0;
>     s->mac_reg[index] = val & 0xffff;
> +    if (e1000_has_rxbufs(s, 1)) {
> +        qemu_flush_queued_packets(&s->nic->nc);
> +    }
>  }
>
>  static void
> diff --git a/hw/virtio-net.c b/hw/virtio-net.c
> index 3f190d4..0974945 100644
> --- a/hw/virtio-net.c
> +++ b/hw/virtio-net.c
> @@ -447,10 +447,6 @@ static void virtio_net_handle_rx(VirtIODevice *vdev,
> VirtQueue *vq)
>     VirtIONet *n = to_virtio_net(vdev);
>
>     qemu_flush_queued_packets(&n->nic->nc);
> -
> -    /* We now have RX buffers, signal to the IO thread to break out of the
> -     * select to re-poll the tap file descriptor */
> -    qemu_notify_event();
>  }
>
>  static int virtio_net_can_receive(VLANClientState *nc)
> diff --git a/net.c b/net.c
> index 1922d8a..fa846ae 100644
> --- a/net.c
> +++ b/net.c
> @@ -491,7 +491,12 @@ void qemu_flush_queued_packets(VLANClientState *vc)
>         queue = vc->send_queue;
>     }
>
> -    qemu_net_queue_flush(queue);
> +    if (qemu_net_queue_flush(queue)) {
> +        /* We emptied the queue successfully, signal to the IO thread to
> repoll
> +         * the file descriptor (for tap, for example).
> +         */
> +        qemu_notify_event();
> +    }
>  }
>
>  static ssize_t qemu_send_packet_async_with_flags(VLANClientState *sender,
> diff --git a/net/queue.c b/net/queue.c
> index 1ab5247..fd1c7e6 100644
> --- a/net/queue.c
> +++ b/net/queue.c
> @@ -232,7 +232,7 @@ void qemu_net_queue_purge(NetQueue *queue,
> VLANClientState *from)
>     }
>  }
>
> -void qemu_net_queue_flush(NetQueue *queue)
> +bool qemu_net_queue_flush(NetQueue *queue)
>  {
>     while (!QTAILQ_EMPTY(&queue->packets)) {
>         NetPacket *packet;
> @@ -248,7 +248,7 @@ void qemu_net_queue_flush(NetQueue *queue)
>                                      packet->size);
>         if (ret == 0) {
>             QTAILQ_INSERT_HEAD(&queue->packets, packet, entry);
> -            break;
> +            return 0;
>         }
>
>         if (packet->sent_cb) {
> @@ -257,4 +257,5 @@ void qemu_net_queue_flush(NetQueue *queue)
>
>         g_free(packet);
>     }
> +    return 1;
>  }
> diff --git a/net/queue.h b/net/queue.h
> index a31958e..4bf6d3c 100644
> --- a/net/queue.h
> +++ b/net/queue.h
> @@ -66,6 +66,6 @@ ssize_t qemu_net_queue_send_iov(NetQueue *queue,
>                                 NetPacketSent *sent_cb);
>
>  void qemu_net_queue_purge(NetQueue *queue, VLANClientState *from);
> -void qemu_net_queue_flush(NetQueue *queue);
> +bool qemu_net_queue_flush(NetQueue *queue);
>
>  #endif /* QEMU_NET_QUEUE_H */
>



-- 
-----------------------------------------+-------------------------------
 Prof. Luigi RIZZO, rizzo@iet.unipi.it  . Dip. di Ing. dell'Informazione
 http://www.iet.unipi.it/~luigi/        . Universita` di Pisa
 TEL      +39-050-2211611               . via Diotisalvi 2
 Mobile   +39-338-6809875               . 56122 PISA (Italy)
-----------------------------------------+-------------------------------

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Re: [Qemu-devel] forgotten commit ? (Re: Proposed patch: huge RX speedup for hw/e1000.c)

[Paolo Bonzini]

Il 24/07/2012 18:49, Luigi Rizzo ha scritto:
> Paolo,
> a few weeks ago you posted the patch below but apparently
> it did not get in after my 'tested-by' reply of June C1st4th
> I'd like to confirm that your patch works perfectly for me.
> 
> Tested-by: Luigi Rizzo <rizzo@iet.unipi.it>

It's on the todo list. :)

Paolo

[Qemu-devel] forgotten commit ? (Re: Proposed patch: huge RX speedup for hw/e1000.c)

[Luigi Rizzo]

Paolo,
a few weeks ago you posted the patch below but apparently
it did not get in after my 'tested-by' reply of June C1st4th
I'd like to confirm that your patch works perfectly for me.

Tested-by: Luigi Rizzo <rizzo@iet.unipi.it>

cheers
luigi

On Thu, May 31, 2012 at 01:03:35PM +0200, Paolo Bonzini wrote:
> Il 31/05/2012 12:40, Jan Kiszka ha scritto:
> > On 2012-05-31 12:03, Paolo Bonzini wrote:
> >> Il 31/05/2012 10:23, Jan Kiszka ha scritto:
> >>>>> @@ -922,6 +923,7 @@ set_rdt(E1000State *s, int index, uint32_t val)
> >>>>>  {
> >>>>>      s->check_rxov = 0;
> >>>>>      s->mac_reg[index] = val & 0xffff;
> >>>>> +    qemu_notify_event();
> >>> This still looks like the wrong tool: Packets that can't be delivered
> >>> are queued.
> >>
> >> Packets that are read from the tap but can't be delivered are queued;
> >> packets that are left on the tap need qemu_notify_event to be flushed.
> >>
> >>> So we need to flush the queue and clear the blocked delivery
> >>> there. qemu_flush_queued_packets appears more appropriate for this.
> >>
> >> Right, and qemu_flush_queued_packets needs to call qemu_notify_event
> >> which makes the call in virtio-net unnecessary.
> >>
> >> Paolo
> >>
> >> diff --git a/hw/e1000.c b/hw/e1000.c
> >> index 4573f13..43d933a 100644
> >> --- a/hw/e1000.c
> >> +++ b/hw/e1000.c
> >> @@ -295,6 +295,7 @@ set_rx_control(E1000State *s, int index, uint32_t val)
> >>      s->rxbuf_min_shift = ((val / E1000_RCTL_RDMTS_QUAT) & 3) + 1;
> >>      DBGOUT(RX, "RCTL: %d, mac_reg[RCTL] = 0x%x\n", s->mac_reg[RDT],
> >>             s->mac_reg[RCTL]);
> >> +    qemu_flush_queued_packets(&s->nic->nc);
> >>  }
> >>  
> >>  static void
> >> @@ -926,6 +927,9 @@ set_rdt(E1000State *s, int index, uint32_t val)
> >>  {
> >>      s->check_rxov = 0;
> >>      s->mac_reg[index] = val & 0xffff;
> >> +    if (e1000_has_rxbufs(s, 1)) {
> >> +        qemu_flush_queued_packets(&s->nic->nc);
> >> +    }
> >>  }
> >>  
> >>  static void
> >> diff --git a/hw/virtio-net.c b/hw/virtio-net.c
> >> index 3f190d4..0974945 100644
> >> --- a/hw/virtio-net.c
> >> +++ b/hw/virtio-net.c
> >> @@ -447,10 +447,6 @@ static void virtio_net_handle_rx(VirtIODevice *vdev, VirtQueue *vq)
> >>      VirtIONet *n = to_virtio_net(vdev);
> >>  
> >>      qemu_flush_queued_packets(&n->nic->nc);
> >> -
> >> -    /* We now have RX buffers, signal to the IO thread to break out of the
> >> -     * select to re-poll the tap file descriptor */
> >> -    qemu_notify_event();
> >>  }
> >>  
> >>  static int virtio_net_can_receive(VLANClientState *nc)
> >> diff --git a/net.c b/net.c
> >> index 1922d8a..fa846ae 100644
> >> --- a/net.c
> >> +++ b/net.c
> >> @@ -491,7 +491,12 @@ void qemu_flush_queued_packets(VLANClientState *vc)
> >>          queue = vc->send_queue;
> >>      }
> >>  
> >> -    qemu_net_queue_flush(queue);
> >> +    if (qemu_net_queue_flush(queue)) {
> >> +        /* We emptied the queue successfully, signal to the IO thread to repoll
> >> +         * the file descriptor (for tap, for example).
> >> +         */
> >> +        qemu_notify_event();
> >> +    }
> >>  }
> >>  
> >>  static ssize_t qemu_send_packet_async_with_flags(VLANClientState *sender,
> >> diff --git a/net/queue.c b/net/queue.c
> >> index 1ab5247..fd1c7e6 100644
> >> --- a/net/queue.c
> >> +++ b/net/queue.c
> >> @@ -232,7 +232,7 @@ void qemu_net_queue_purge(NetQueue *queue, VLANClientState *from)
> >>      }
> >>  }
> >>  
> >> -void qemu_net_queue_flush(NetQueue *queue)
> >> +bool qemu_net_queue_flush(NetQueue *queue)
> >>  {
> >>      while (!QTAILQ_EMPTY(&queue->packets)) {
> >>          NetPacket *packet;
> >> @@ -248,7 +248,7 @@ void qemu_net_queue_flush(NetQueue *queue)
> >>                                       packet->size);
> >>          if (ret == 0) {
> >>              QTAILQ_INSERT_HEAD(&queue->packets, packet, entry);
> >> -            break;
> >> +            return 0;
> >>          }
> >>  
> >>          if (packet->sent_cb) {
> >> @@ -257,4 +257,5 @@ void qemu_net_queue_flush(NetQueue *queue)
> >>  
> >>          g_free(packet);
> >>      }
> >> +    return 1;
> >>  }
> >> diff --git a/net/queue.h b/net/queue.h
> >> index a31958e..4bf6d3c 100644
> >> --- a/net/queue.h
> >> +++ b/net/queue.h
> >> @@ -66,6 +66,6 @@ ssize_t qemu_net_queue_send_iov(NetQueue *queue,
> >>                                  NetPacketSent *sent_cb);
> >>  
> >>  void qemu_net_queue_purge(NetQueue *queue, VLANClientState *from);
> >> -void qemu_net_queue_flush(NetQueue *queue);
> >> +bool qemu_net_queue_flush(NetQueue *queue);
> >>  
> >>  #endif /* QEMU_NET_QUEUE_H */
> > 
> > Looks good.
> 
> Luigi, please reply with a Tested-by when possible.
> 
> Paolo