Re: CVS commit: src/sys/arch/xen/xen

[YAMAMOTO Takashi <yamt%mwd.biglobe.ne.jp@localhost>]

> Module Name:  src
> Committed By: bouyer
> Date:         Sun Oct  2 21:49:23 UTC 2005
> 
> Modified Files:
>       src/sys/arch/xen/xen: xennetback.c
> 
> Log Message:
> Major improvements to the network backend, leading to a 0-copy transmit and
> receive system:
> - on the receive side, attach the mapped buffer as external storage
>   instead of copying it. As a mapped buffer may not live much longer, we
>   have to deal with the fact that one page of buffer may containt several
>   packets, and it's not possible to map them several times. Use a hashed list
>   to keep track of mapped pages, and use reference counters.

- are you sure that it isn't possible to map a page several times?
  to me, linux netback doesn't seem to do anything special for it.

- as you defer ack until xennetback_tx_free and the mbuf can live ~forever,
  you can capture all buffers.
  (i think that linux netback has the same problem.)

YAMAMOTO Takashi