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

[Paolo Bonzini]

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