On Tue, 2007-09-25 at 12:15 +0200, Or Gerlitz wrote:
> Eli Cohen wrote:
> > Add checksum offload support to the core
> > A device that publishes IB_DEVICE_IP_CSUM actually supports
> > calculating checksum on transmit and provides indication whether
> > the checksum is OK on receive.
>
> Hi Eli,
>
> From the discussion over the "IB/ipoib: S/G and HW checksum support"
> thread, I understand that Linux actually never offloads the IP checksum
> calculation to the HW but rather only the TCP and UDP checksum.
>
> I find it more clear if the device capability (same for the send flag)
> name would follow one of these:
> > #define NETIF_F_IP_CSUM 2 /* Can checksum TCP/UDP over IPv4. */
> > #define NETIF_F_NO_CSUM 4 /* Does not require checksum. F.e.
> > loopack. */
> > #define NETIF_F_HW_CSUM 8 /* Can checksum all the packets. */
> > #define NETIF_F_IPV6_CSUM 16 /* Can checksum TCP/UDP over IPV6 */
>
> Or.
I am not sure that defining all kinds of capabilities to the device are
useful. For example if a device defines only IP checksum than there is
no useful.
>
> > Index: ofa_1_3_dev_kernel/include/rdma/ib_verbs.h
>
> > enum ib_cq_notify_flags {
> > @@ -615,7 +617,9 @@ enum ib_send_flags {
> > IB_SEND_FENCE = 1,
> > IB_SEND_SIGNALED = (1<<1),
> > IB_SEND_SOLICITED = (1<<2),
> > - IB_SEND_INLINE = (1<<3)
> > + IB_SEND_INLINE = (1<<3),
> > + IB_SEND_IP_CSUM = (1<<4),
> there's no point for the HW to compute the IP csum, asking this is a
> pure waste, since the stack always does it
> > + IB_SEND_UDP_TCP_CSUM = (1<<5)
> > };
>
I am not sure this is always true but anyway it is not a waste since
computing the checksum does put more "work" on the hardware.
_______________________________________________
general mailing list
[email protected]
http://lists.openfabrics.org/cgi-bin/mailman/listinfo/general
To unsubscribe, please visit http://openib.org/mailman/listinfo/openib-general
