Re: [Xen-devel] about the network speed is too slow with vtd on Xen-3.2

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

Have you considered not printing so much? After passthru is set up you
should only be logging on error conditions.

 -- Keir

On 16/6/08 11:27, "Zhang, Li" <li.zhang@xxxxxxxxx> wrote:

> Hi, Keir
> With 3.2-tree, if we assigned NIC to guest, we copy a file with 'scp'
> command. the speed shows only about 2M in 1000M LAN. It is because that
> when we add the guest_level, too many messages in the serial are
> printed. The patch 17509 of Xen unstable can be ported to this tree to
> fix it. 
> 
> diff -r b39b6ab402ee xen/drivers/char/serial.c
> --- a/xen/drivers/char/serial.c Fri Jun 13 13:59:22 2008 +0100
> +++ b/xen/drivers/char/serial.c Mon Jun 16 17:49:48 2008 +0800
> @@ -14,6 +14,9 @@
>  #include <xen/sched.h>
>  #include <xen/mm.h>
>  #include <xen/serial.h>
> +
> +/* Never drop characters, even if the async transmit buffer fills. */
> +/* #define SERIAL_NEVER_DROP_CHARS 1 */
>  
>  static struct serial_port com[2] = {
>      { .rx_lock = SPIN_LOCK_UNLOCKED, .tx_lock = SPIN_LOCK_UNLOCKED },
> @@ -81,22 +84,24 @@
>  
>  static void __serial_putc(struct serial_port *port, char c)
>  {
> -    int i;
> -
>      if ( (port->txbuf != NULL) && !port->sync )
>      {
>          /* Interrupt-driven (asynchronous) transmitter. */
> +#ifdef SERIAL_NEVER_DROP_CHARS
>          if ( (port->txbufp - port->txbufc) == SERIAL_TXBUFSZ )
>          {
> -            /* Buffer is full: we spin, but could alternatively drop
> chars. */
> +            /* Buffer is full: we spin waiting for space to appear */
> +            int i;
>              while ( !port->driver->tx_empty(port) )
>                  cpu_relax();
>              for ( i = 0; i < port->tx_fifo_size; i++ )
>                  port->driver->putc(
>                      port,
> port->txbuf[MASK_SERIAL_TXBUF_IDX(port->txbufc++)]);
>              port->txbuf[MASK_SERIAL_TXBUF_IDX(port->txbufp++)] = c;
> +            return;
>          }
> -        else if ( ((port->txbufp - port->txbufc) == 0) &&
> +#endif
> +        if ( ((port->txbufp - port->txbufc) == 0) &&
>                    port->driver->tx_empty(port) )
>          {
>              /* Buffer and UART FIFO are both empty. */
> 
> Thanks
> -Li
> 
> 
> _______________________________________________
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> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel



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