Added documentation for rdma controller to use in legacy mode and using new unified hirerchy.
Signed-off-by: Parav Pandit <pandit.pa...@gmail.com> --- Documentation/cgroup-legacy/rdma.txt | 129 +++++++++++++++++++++++++++++++++++ Documentation/cgroup.txt | 79 +++++++++++++++++++++ 2 files changed, 208 insertions(+) create mode 100644 Documentation/cgroup-legacy/rdma.txt diff --git a/Documentation/cgroup-legacy/rdma.txt b/Documentation/cgroup-legacy/rdma.txt new file mode 100644 index 0000000..70626c5 --- /dev/null +++ b/Documentation/cgroup-legacy/rdma.txt @@ -0,0 +1,129 @@ + RDMA Resource Controller + ------------------------ + +Contents +-------- + +1. Overview + 1-1. What is RDMA resource controller? + 1-2. Why RDMA resource controller needed? + 1-3. How is RDMA resource controller implemented? +2. Usage Examples + +1. Overview + +1-1. What is RDMA resource controller? +------------------------------------- + +RDMA resource controller allows user to limit RDMA/IB specific resources +that a given set of processes can use. These processes are grouped using +RDMA resource controller. + +RDMA resource controller currently allows two different type of resource +pools. +(a) RDMA IB specification level verb resources defined by IB stack +(b) HCA vendor device specific resources + +RDMA resource controller controller allows maximum of upto 64 resources in +a resource pool which is the internal construct of rdma cgroup explained +at later part of this document. + +1-2. Why RDMA resource controller needed? +---------------------------------------- + +Currently user space applications can easily take away all the rdma device +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 leads to service unavailability. + +Therefore RDMA resource controller is needed through which resource consumption +of processes can be limited. Through this controller various different rdma +resources described by IB uverbs layer and any HCA vendor driver can be +accounted. + +1-3. How is RDMA resource controller implemented? +------------------------------------------------ + +rdma cgroup allows limit configuration of resources. These resources are not +defined by the rdma controller. Instead they are defined by the IB stack +and HCA device drivers(optionally). +This provides great flexibility to allow IB stack to define new resources, +without any changes to rdma cgroup. +Rdma cgroup maintains resource accounting per cgroup, per device, per resource +type 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 +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’s not the primary use case. + +Finally mapping of the resource owner pid to cgroup is maintained using +simple hash table to perform quick look-up during resource charing/uncharging +time. + +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. This is done using default +resource pool. Instead of implementing any sort of time markers, default pool +simplifies the design. + +Resource pool is destroyed if it was of default type (not created +by administrative operation) and it’s the last resource getting +deallocated. Resource pool created as administrative operation is not +deleted, as it’s expected to be used in near future. + +If user setting tries to delete all the resource limit +with active resources per device, RDMA cgroup just marks the pool as +default pool with maximum limits for each resource, otherwise it deletes the +default resource pool. + +2. Usage Examples +----------------- + +(a) List available RDMA verb level resources: + +#cat /sys/fs/cgroup/rdma/1/rdma.resource.verb.list +Output: +mlx4_0 uctx ah pd mr srq qp flow + +(b) Configure resource limit: +echo mlx4_0 mr=100 qp=10 ah=2 > /sys/fs/cgroup/rdma/1/rdma.resource.verb.limit +echo ocrdma1 mr=120 qp=20 cq=10 > /sys/fs/cgroup/rdma/2/rdma.resource.verb.limit + +(c) Query resource limit: +cat /sys/fs/cgroup/rdma/2/rdma.resource.verb.limit +#Output: +mlx4_0 mr=100 qp=10 ah=2 +ocrdma1 mr=120 qp=20 cq=10 + +(d) Query current usage: +cat /sys/fs/cgroup/rdma/2/rdma.resource.verb.usage +#Output: +mlx4_0 mr=95 qp=8 ah=2 +ocrdma1 mr=0 qp=20 cq=10 + +(e) Delete resource limit: +echo mlx4_0 remove > /sys/fs/cgroup/rdma/1/rdma.resource.verb.limit + +(f) List available HCA HW specific resources: (optional) +cat /sys/fs/cgroup/rdma/1/rdma.hw.verb.list +vendor1 hw_qp hw_cq hw_timer + +(g) Configure hw specific resource limit: +echo vendor1 hw_qp=56 > /sys/fs/cgroup/rdma/2/rdma.resource.hw.limit diff --git a/Documentation/cgroup.txt b/Documentation/cgroup.txt index 983ba63..57eb59c 100644 --- a/Documentation/cgroup.txt +++ b/Documentation/cgroup.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 @@ -1017,6 +1019,83 @@ writeback as follows. total available memory and applied the same way as vm.dirty[_background]_ratio. +5-4. RDMA + +The "rdma" controller regulates the distribution of RDMA resources. +This controller implements both RDMA/IB verb level and RDMA HCA +driver level resource distribution. + +5-4-1. RDMA Interface Files + + rdma.resource.verb.list + + A read-only file that exists for all the cgroups that describes + which all verb specific resources of a given device can be + distributed and accounted. + + Lines are keyed by device name and are not ordered. + Each line contains space separated resource name that can be + distributed. + + An example for mlx4_0 device follows. + + mlx4_0 ah cq pd mr qp flow srq + + rdma.resource.verb.limit + A readwrite file that exists for all the cgroups that describes + current configured verbs 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. + + An example for mlx4 and ocrdma device follows. + + mlx4_0 mr=1000 qp=104 ah=2 + ocrdma1 mr=900 qp=89 cq=10 + + rdma.resource.verb.usage + A read-only file that describes current resource usage. + It exists for all the cgroup including root. + + An example for mlx4 and ocrdma device follows. + + mlx4_0 mr=1000 qp=102 ah=2 + ocrdma1 mr=900 qp=79 cq=10 + + rdma.resource.verb.failcnt + A read-only file that describes resource allocation failure + count for a given resource type of a particular device. + It exists for all the cgroup including root. + + An example for mlx4 and ocrdma device follows. + + mlx4_0 mr=0 qp=1 ah=1 + ocrdma1 mr=2 qp=1 cq=1 + + rdma.resource.hw.list + + A read-only file that exists for all the cgroups that describes + which all HCA hardware specific resources of a given device can be + distributed and accounted. + + rdma.resource.hw.limit + A readwrite file that exists for all the cgroups that describes + current configured HCA hardware 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. + + rdma.resource.hw.usage + A read-only file that describes current resource usage. + It exists for all the cgroup including root. + + rdma.resource.hw.failcnt + A read-only file that describes HCA hardware resource + allocation failure count for a given resource type of + a particular device. + It exists for all the cgroup including root. 6. 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