Automatic pinning and unpinning of virtual pages for remote direct memory access
In one exemplary embodiment, a computer-implemented method includes receiving, at a remote direct memory access (RDMA) device, a plurality of RDMA requests referencing a plurality of virtual pages. Data transfers are scheduled for the plurality of virtual pages, wherein the scheduling occurs at the RDMA device. The number of the virtual pages that are currently pinned is limited for the RDMA requests based on a predetermined pinned page limit.
1. A system comprising
a remote direct memory access (RDMA) device configured to:
receive, from two or more user applications, a plurality of RDMA requests referencing a plurality of virtual pages;
schedule data transfers for the two or more user applications, wherein the scheduling comprises:
ordering the plurality of RDMA requests according to when they were received; and
performing a first RDMA request out of order based on the first RDMA request referencing a virtual page that is currently pinned; and
limit the number of the virtual pages that are currently pinned for the RDMA requests based on a predetermined pinned page limit; and
software configured to pin the plurality of virtual pages according to the scheduling of the RDMA device.
2. The system of claim 1 , the RDMA device being further configured to generate a pin fault related to a first virtual page of the plurality of virtual pages, and the software being further configured to pin and register the first virtual page in response to the pin fault.
3. The system of claim 1 , the RDMA device being further configured to determine whether the first virtual page of the plurality of virtual pages is currently pinned.
4. The system of claim 1 , the RDMA device being further configured to:
complete a first subset of the plurality of RDMA requests, wherein a second subset of the RDMA requests has yet to be completed; and
determine whether a first virtual page that is currently pinned is referenced by the second subset of the RDMA requests.
5. The system of claim 1 , wherein the RDMA device is configured to schedule the data transfers for the plurality of virtual pages at least by managing an amount of time taken in total to pin the plurality of virtual pages for the plurality of RDMA requests.
6. The system of claim 1 , wherein the RDMA device is configured to schedule the data transfers for the plurality of virtual pages at least by giving priority to a first subset of the plurality of virtual pages, wherein the first subset comprises virtual pages that are currently pinned.
7. The system of claim 1 , the RDMA device being further configured to:
predict that a first RDMA request will be received referencing a first virtual page; and
request that the first virtual page be pinned based on the prediction.