xen-devel
[Xen-devel] Re: [7/11] [NET] back: Added tx queue
On 7 Jul 2006, at 15:19, Herbert Xu wrote:
ET] back: Added tx queue
This patch adds a tx queue to the backend if the frontend supports rx
refill notification. A queue is needed because SG/TSO greatly reduces
the number of packets that can be stored in the rx ring. Given an rx
ring with 256 entries, a maximum TSO packet can occupy as many as 18
entries, meaning that the entire ring can only hold 14 packets. This
is too small at high bandwidths with large TCP RX windows.
Having a tx queue does not present a new security risk as the queue is
a fixed size buffer just like rx ring. So each guest can only hold a
fixed amount of memory (proportional to the tx queue length) on the
host.
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
What's the default queue size? It shouldn't be too large if each packet
can be 64kB!
Also, what does NETIF_F_LLTX have to do with whether we have a queue or
not -- couldn't we set that all the time? And you set queue length to 1
in the other case -- what's wrong with zero? Seems a saner value when
there is no queue: or do we need to commit to having *some* queue at
register_netdevice() time, and there's no way to go back from that by
the time we find out if netfront supports rx refill notifications (so
at that point we cannot change queue len to zero)?
-- Keir
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- [Xen-devel] Re: [3/11] [NET] front: Stop using rx->id, (continued)
[Xen-devel] [4/11] [NET] front: Move rx req pushing to one spot , Herbert Xu
[Xen-devel] [5/11] [NET] back: Replace netif->active with netif_carrier_ok , Herbert Xu
[Xen-devel] [6/11] [NET] front: Added feature-rx-notify , Herbert Xu
[Xen-devel] [7/11] [NET] back: Added tx queue , Herbert Xu
- [Xen-devel] Re: [7/11] [NET] back: Added tx queue,
Keir Fraser <=
[Xen-devel] [8/11] [NET] front: Add SG support , Herbert Xu
[Xen-devel] [9/11] [NET] back: Transmit SG packets if supported , Herbert Xu
[Xen-devel] [10/11] [NET] front: Add TSO support , Herbert Xu
[Xen-devel] [11/11] [NET] back: Transmit TSO packets if supported , Herbert Xu
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