On 01/11/15 10:40, Sagi Grimberg wrote: > I would say there is no need for specific coordination from iSCSI PoV. > This is exactly what flow steering is designed for. As I see it, in > order to get the TX/RX to match rings, the user can attach 5-tuple rules > (using standard ethtool) to steer packets to the right rings.
Hello Sagi, Can the 5-tuple rules be chosen such that it is guaranteed that the sockets used to implement per-CPU queues are spread evenly over MSI-X completion vectors ? If not, would it help to add a socket option to the Linux network stack that allows to select the TX ring explicitly, just like ib_create_cq() in the Linux RDMA stack allows to select a completion vector explicitly ? My concerns are as follows: - If the number of queues exceeds the number of MSI-X vectors then I expect that it will be much easier to guarantee even spreading by selecting tx queues explicitly instead of relying on a hashing scheme. - On multi-socket systems it is important to process completion interrupts on the CPU socket from where the I/O was initiated. I'm not sure it is possible to guarantee this when using a hashing algorithm to select the TX ring. Bart. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
