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infinibandrdmamellanoxofed

RDMA Fast Memory Registration (FMR)

I'm developing a system that uses RDMA extensively (on Mellanox hardware) and would like to be able to register memory regions more efficiently/faster.

I have taken a look into Fast Memory Registration and I have a few questions:

  1. Is FMR going away? From here [1] it seems it might get removed/replaced soon.

  2. Is there any user-space code out there that makes use of this feature? There are only a few threads online discussing this and mostly in the context of kernel modules.

Any useful pointers would be greatly appreciated.

[1] https://jira.hpdd.intel.com/browse/LU-5783

Solution

  • It seems that kernel developers would like to get FMR removed. See for example this future of FMR thread on linux-rdma.

    FMR (and FRWR) are only used in the kernel. User-space isn't trusted to use these operations as they allow access to the physical address space and could break process isolation.