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Merge branch 'for-4.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Browse Source 
Pull cgroup updates from Tejun Heo:
 "Several noteworthy changes.

   - Parav's rdma controller is finally merged. It is very straight
     forward and can limit the abosolute numbers of common rdma
     constructs used by different cgroups.

   - kernel/cgroup.c got too chubby and disorganized. Created
     kernel/cgroup/ subdirectory and moved all cgroup related files
     under kernel/ there and reorganized the core code. This hurts for
     backporting patches but was long overdue.

   - cgroup v2 process listing reimplemented so that it no longer
     depends on allocating a buffer large enough to cache the entire
     result to sort and uniq the output. v2 has always mangled the sort
     order to ensure that users don't depend on the sorted output, so
     this shouldn't surprise anybody. This makes the pid listing
     functions use the same iterators that are used internally, which
     have to have the same iterating capabilities anyway.

   - perf cgroup filtering now works automatically on cgroup v2. This
     patch was posted a long time ago but somehow fell through the
     cracks.

   - misc fixes asnd documentation updates"

* 'for-4.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (27 commits)
  kernfs: fix locking around kernfs_ops->release() callback
  cgroup: drop the matching uid requirement on migration for cgroup v2
  cgroup, perf_event: make perf_event controller work on cgroup2 hierarchy
  cgroup: misc cleanups
  cgroup: call subsys->*attach() only for subsystems which are actually affected by migration
  cgroup: track migration context in cgroup_mgctx
  cgroup: cosmetic update to cgroup_taskset_add()
  rdmacg: Fixed uninitialized current resource usage
  cgroup: Add missing cgroup-v2 PID controller documentation.
  rdmacg: Added documentation for rdmacg
  IB/core: added support to use rdma cgroup controller
  rdmacg: Added rdma cgroup controller
  cgroup: fix a comment typo
  cgroup: fix RCU related sparse warnings
  cgroup: move namespace code to kernel/cgroup/namespace.c
  cgroup: rename functions for consistency
  cgroup: move v1 mount functions to kernel/cgroup/cgroup-v1.c
  cgroup: separate out cgroup1_kf_syscall_ops
  cgroup: refactor mount path and clearly distinguish v1 and v2 paths
  cgroup: move cgroup v1 specific code to kernel/cgroup/cgroup-v1.c
  ...
This commit is contained in:
Linus Torvalds
2017-02-27 21:41:08 -08:00
parent fb15a78210 f83f3c5156
commit f7878dc3a9
30 changed files with 3267 additions and 1901 deletions
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109
Documentation/cgroup-v1/rdma.txt Normal file
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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