(RDMA: Remote Direct Memory Access)
RDMA Live Migration Specification, Version # 1
==============================================
-Wiki: http://wiki.qemu.org/Features/RDMALiveMigration
+Wiki: http://wiki.qemu-project.org/Features/RDMALiveMigration
high-performance RDMA hardware using the following command:
QEMU Monitor Command:
-$ migrate_set_capability x-rdma-pin-all on # disabled by default
+$ migrate_set_capability rdma-pin-all on # disabled by default
Performing this action will cause all 8GB to be pinned, so if that's
not what you want, then please ignore this step altogether.
Next, on the destination machine, add the following to the QEMU command line:
-qemu ..... -incoming x-rdma:host:port
+qemu ..... -incoming rdma:host:port
Finally, perform the actual migration on the source machine:
QEMU Monitor Command:
-$ migrate -d x-rdma:host:port
+$ migrate -d rdma:host:port
PERFORMANCE
===========
active use and the VM itself is completely idle using the same 40 gbps
infiniband link:
-1. x-rdma-pin-all disabled total time: approximately 7.5 seconds @ 9.5 Gbps
-2. x-rdma-pin-all enabled total time: approximately 4 seconds @ 26 Gbps
+1. rdma-pin-all disabled total time: approximately 7.5 seconds @ 9.5 Gbps
+2. rdma-pin-all enabled total time: approximately 4 seconds @ 26 Gbps
These numbers would of course scale up to whatever size virtual machine
you have to migrate using RDMA.
check this field and register all requests found in the array of commands located
in the data portion and return an equal number of results in the response.
The maximum number of repeats is hard-coded to 4096. This is a conservative
-limit based on the maximum size of a SEND message along with emperical
+limit based on the maximum size of a SEND message along with empirical
observations on the maximum future benefit of simultaneous page registrations.
The 'type' field has 12 different command values:
TODO:
=====
-1. 'migrate x-rdma:host:port' and '-incoming x-rdma' options will be
- renamed to 'rdma' after the experimental phase of this work has
- completed upstream.
-2. Currently, 'ulimit -l' mlock() limits as well as cgroups swap limits
+1. Currently, 'ulimit -l' mlock() limits as well as cgroups swap limits
are not compatible with infinband memory pinning and will result in
an aborted migration (but with the source VM left unaffected).
-3. Use of the recent /proc/<pid>/pagemap would likely speed up
+2. Use of the recent /proc/<pid>/pagemap would likely speed up
the use of KSM and ballooning while using RDMA.
-4. Also, some form of balloon-device usage tracking would also
+3. Also, some form of balloon-device usage tracking would also
help alleviate some issues.
-5. Move UNREGISTER requests to a separate thread.
-6. Use LRU to provide more fine-grained direction of UNREGISTER
+4. Use LRU to provide more fine-grained direction of UNREGISTER
requests for unpinning memory in an overcommitted environment.
-7. Expose UNREGISTER support to the user by way of workload-specific
+5. Expose UNREGISTER support to the user by way of workload-specific
hints about application behavior.