On Fri, Mar 01, 2019 at 09:50:46AM -0800, Bart Van Assche wrote: > On Thu, 2019-02-28 at 15:22 +0200, Leon Romanovsky wrote: > > On Thu, Feb 28, 2019 at 07:39:25AM -0500, Dennis Dalessandro wrote: > > > On 2/27/2019 2:49 PM, Parav Pandit wrote: > > > > Giving low priority to most of them, I think desire to have loopback rdma device are below. > > > > 1. rxe is not ready for adding IB link types and large code restructure to avoid skb processing in it. Pretty large rewrite to skip skbs. > > > > 2. stability and reasonable performance > > > > 3. maintainability > > > > > > I don't see how this is more maintainable. We are adding a new driver, a new > > > user space provider. So I don't see that as being a reason for adding this. > > > > Agree too, it is so tempting to write something new instead of fixing. > > Hi Leon, > > Early 2018 there was a discussion at LSF/MM about how to implement a high- > performance block driver in user space. A highly optimized RDMA loopback > driver in combination with e.g. the NVMeOF kernel initiator driver and a > NVMeOF target driver in user space could be used for this purpose. Do you > think it is possible to make loopback in the rdma_rxe driver as fast as > in Parav Pandit's driver? See also Matthew Wilcox, [LSF/MM TOPIC] A high- > performance userspace block driver, January 2018 > (https://www.spinics.net/lists/linux-fsdevel/msg120674.html). I don't see any reason to say no, once RXE and SIW detect that they were requested operate on loopback, they can "perform" extra optimizations to do it extremely fast. In case of RXE, that driver will skip SW ICRC calculations. Thanks > > Thanks, > > Bart. >
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