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| -rw-r--r-- | Documentation/cgroup-v1/rdma.txt | 109 | ||||
| -rw-r--r-- | Documentation/cgroup-v2.txt | 38 |
2 files changed, 147 insertions, 0 deletions
diff --git a/Documentation/cgroup-v1/rdma.txt b/Documentation/cgroup-v1/rdma.txt new file mode 100644 index 000000000000..af618171e0eb --- /dev/null +++ b/Documentation/cgroup-v1/rdma.txt @@ -0,0 +1,109 @@ + RDMA Controller + ---------------- + +Contents +-------- + +1. Overview + 1-1. What is RDMA controller? + 1-2. Why RDMA controller needed? + 1-3. How is RDMA controller implemented? +2. Usage Examples + +1. Overview + +1-1. What is RDMA controller? +----------------------------- + +RDMA controller allows user to limit RDMA/IB specific resources that a given +set of processes can use. These processes are grouped using RDMA controller. + +RDMA controller defines two resources which can be limited for processes of a +cgroup. + +1-2. Why RDMA controller needed? +-------------------------------- + +Currently user space applications can easily take away all the rdma verb +specific resources such as AH, CQ, QP, MR etc. Due to which other applications +in other cgroup or kernel space ULPs may not even get chance to allocate any +rdma resources. This can leads to service unavailability. + +Therefore RDMA controller is needed through which resource consumption +of processes can be limited. Through this controller different rdma +resources can be accounted. + +1-3. How is RDMA controller implemented? +---------------------------------------- + +RDMA cgroup allows limit configuration of resources. Rdma cgroup maintains +resource accounting per cgroup, per device using resource pool structure. +Each such resource pool is limited up to 64 resources in given resource pool +by rdma cgroup, which can be extended later if required. + +This resource pool object is linked to the cgroup css. Typically there +are 0 to 4 resource pool instances per cgroup, per device in most use cases. +But nothing limits to have it more. At present hundreds of RDMA devices per +single cgroup may not be handled optimally, however there is no +known use case or requirement for such configuration either. + +Since RDMA resources can be allocated from any process and can be freed by any +of the child processes which shares the address space, rdma resources are +always owned by the creator cgroup css. This allows process migration from one +to other cgroup without major complexity of transferring resource ownership; +because such ownership is not really present due to shared nature of +rdma resources. Linking resources around css also ensures that cgroups can be +deleted after processes migrated. This allow progress migration as well with +active resources, even though that is not a primary use case. + +Whenever RDMA resource charging occurs, owner rdma cgroup is returned to +the caller. Same rdma cgroup should be passed while uncharging the resource. +This also allows process migrated with active RDMA resource to charge +to new owner cgroup for new resource. It also allows to uncharge resource of +a process from previously charged cgroup which is migrated to new cgroup, +even though that is not a primary use case. + +Resource pool object is created in following situations. +(a) User sets the limit and no previous resource pool exist for the device +of interest for the cgroup. +(b) No resource limits were configured, but IB/RDMA stack tries to +charge the resource. So that it correctly uncharge them when applications are +running without limits and later on when limits are enforced during uncharging, +otherwise usage count will drop to negative. + +Resource pool is destroyed if all the resource limits are set to max and +it is the last resource getting deallocated. + +User should set all the limit to max value if it intents to remove/unconfigure +the resource pool for a particular device. + +IB stack honors limits enforced by the rdma controller. When application +query about maximum resource limits of IB device, it returns minimum of +what is configured by user for a given cgroup and what is supported by +IB device. + +Following resources can be accounted by rdma controller. + hca_handle Maximum number of HCA Handles + hca_object Maximum number of HCA Objects + +2. Usage Examples +----------------- + +(a) Configure resource limit: +echo mlx4_0 hca_handle=2 hca_object=2000 > /sys/fs/cgroup/rdma/1/rdma.max +echo ocrdma1 hca_handle=3 > /sys/fs/cgroup/rdma/2/rdma.max + +(b) Query resource limit: +cat /sys/fs/cgroup/rdma/2/rdma.max +#Output: +mlx4_0 hca_handle=2 hca_object=2000 +ocrdma1 hca_handle=3 hca_object=max + +(c) Query current usage: +cat /sys/fs/cgroup/rdma/2/rdma.current +#Output: +mlx4_0 hca_handle=1 hca_object=20 +ocrdma1 hca_handle=1 hca_object=23 + +(d) Delete resource limit: +echo echo mlx4_0 hca_handle=max hca_object=max > /sys/fs/cgroup/rdma/1/rdma.max diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt index 4cc07ce3b8dd..94350d79e169 100644 --- a/Documentation/cgroup-v2.txt +++ b/Documentation/cgroup-v2.txt @@ -47,6 +47,8 @@ CONTENTS 5-3. IO 5-3-1. IO Interface Files 5-3-2. Writeback + 5-4. RDMA + 5-4-1. RDMA Interface Files 6. Namespace 6-1. Basics 6-2. The Root and Views @@ -1119,6 +1121,42 @@ writeback as follows. vm.dirty[_background]_ratio. +5-4. RDMA + +The "rdma" controller regulates the distribution and accounting of +of RDMA resources. + +5-4-1. RDMA Interface Files + + rdma.max + A readwrite nested-keyed file that exists for all the cgroups + except root that describes current configured resource limit + for a RDMA/IB device. + + Lines are keyed by device name and are not ordered. + Each line contains space separated resource name and its configured + limit that can be distributed. + + The following nested keys are defined. + + hca_handle Maximum number of HCA Handles + hca_object Maximum number of HCA Objects + + An example for mlx4 and ocrdma device follows. + + mlx4_0 hca_handle=2 hca_object=2000 + ocrdma1 hca_handle=3 hca_object=max + + rdma.current + A read-only file that describes current resource usage. + It exists for all the cgroup except root. + + An example for mlx4 and ocrdma device follows. + + mlx4_0 hca_handle=1 hca_object=20 + ocrdma1 hca_handle=1 hca_object=23 + + 6. Namespace 6-1. Basics |