On Sun, Sep 14, 2014 at 9:46 PM, Yuval Shaia <yuval.shaia@xxxxxxxxxx> wrote: > By default, IPoIB-CM driver uses 64k MTU. Larger MTU gives better performance. > This MTU plus overhead puts the memory allocation for IP based packets at 32 4k pages > (order 5), So if we make sure that the advertized netdevice MTU is 64K minus that over head we're back to order four allocation and problem is solved? note that RFC 4755 makes sure that the MTU is negotiated in both directions, so it can have any value, specifically 64K - that epsilon which will hopefully make you happy > [...] The proposal is to tell to network stack that IPoIB-CM supports IP > Checksum offload. This enables Linux IPoIB-CM driver to use Scatter/Gather feature. Network > sends the IP packet without adding the IP Checksum to the header. AFAIK, on the TX side, Linux will always compute the IP checksum, but with this suggestion, not the TCP checksum which is assumed to be computed by the card... so we will have a TCP packet on the wire without checksum. And if this packet goes through gateway it will be dropped at some point, agree? -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
