On Fri, Jun 18, 2010 at 01:26:49PM +0800, Xin, Xiaohui wrote: > > Herbert, > I have questions about the idea above: > 1) Since netdev_alloc_skb() is still there, and we only modify alloc_page(), > then we don't need napi_gro_frags() any more, the driver's original receiving > function is ok. Right? Well I was actually thinking about converting all drivers that need this to napi_gro_frags. But now that you mention it, yes we could still keep the old interface to minimise the work. > 2) Is napi_gro_frags() only suitable for TCP protocol packet? > I have done a small test for ixgbe driver to let it only allocate paged buffers > and found kernel hangs when napi_gro_frags() receives an ARP packet. It should work with any packet. In fact, I'm pretty sure the other drivers (e.g., cxgb3) use that interface for all packets. > 3) As I have mentioned above, with this idea, netdev_alloc_skb() will allocate > as usual, the data pointed by skb->data will be copied into the first guest buffer. > That means we should reserve sufficient room in guest buffer. For PS mode > supported driver (for example ixgbe), the room will be more than 128. After 128bytes, > we will put the first frag data. Look into virtio-net.c the function page_to_skb() > and receive_mergeable(), that means we should modify guest virtio-net driver to > compute the offset as the parameter for skb_set_frag(). > > How do you think about this? Attached is a patch to how to modify the guest driver. > I reserve 512 bytes as an example, and transfer the header len of the skb in hdr->hdr_len. Expanding the buffer size to 512 bytes to accomodate PS mode looks reasonable to me. However, I don't think we should increase the copy threshold to 512 bytes at the same time. I don't have any figures myself but I think if we are to make such a change it should be a separate one and come with supporting numbers. Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
