Browse Prior Art Database

Real addressing mode for RDMA operations

IP.com Disclosure Number: IPCOM000126449D
Original Publication Date: 2005-Jul-18
Included in the Prior Art Database: 2005-Jul-18
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Abstract

There are certain classes of applications that have privileged access to a remote nodes memory using RDMA. This invention describes a mechanism for using "real addresses" for RDMA operations, thus avoiding the address translation overhead, while maintaining the same level of protection that is used for standard RDMA operations.

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Real addressing mode for RDMA operations

RDMA-capable adapters such as InfiniBand Host Channel Adapters (HCAs) allow efficient transfer of data between nodes without the need for software to copy data. These adapters provide numerous protection checks before allowing access to the remote memory. After these protection checks have completed successfully, the remote adapter translates the virtual address provided in the RDMA request packet, using the address translation tables that were set up when the memory region was registered with the adapter.There are certain classes of applications that have privileged access to the remote nodes memory. For such applications, significant performance benefits can be gained by avoiding the address translation portion of an RDMA operation. Disclosed is a mechanism for using "real addresses" for RDMA operations, thus avoiding the address translation overhead typically associated with these adapters, while maintaining the same level of protection that is used for standard RDMA operations. In order to perform the address translation of an incoming RDMA operation, the adapter needs to fetch a protection table entry and potentially multiple levels of address translation tables. This severely impacts the performance of the operation. It is possible to cache the entries in the adapter, but for large memory regions the probability of a cache hit for all entries is small. This invention describes mechanisms for eliminating the address translation process, whereby only the protection table entry is needed, which improves the performance and in addition is also much m...