Re: [PATCHv11 0/3] rdmacg: IB/core: rdma controller support

[Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

(cc'ing Christoph)

On Mon, Aug 22, 2016 at 06:03:48PM +0530, Parav Pandit wrote:
> rdmacg: IB/core: rdma controller support
> 
> Patch is generated and tested against below Doug's linux-rdma
> git tree.
> 
> URL: git://git.kernel.org/pub/scm/linux/kernel/git/dledford/rdma.git
> Branch: master
> 
> Patchset is also compiled and tested against below Tejun's cgroup tree
> using cgroup v2 mode.
> URL: git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git
> Branch: master
> 
> Overview:
> 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 results into service unavailibility.
> 
> RDMA cgroup addresses this issue by allowing resource accounting,
> limit enforcement on per cgroup, per rdma device basis.
> 
> RDMA uverbs layer will enforce limits on well defined RDMA verb
> resources without any HCA vendor device driver involvement.
> 
> RDMA uverbs layer will not do limit enforcement of HCA hw vendor
> specific resources. Instead rdma cgroup provides set of APIs
> through which vendor specific drivers can do resource accounting
> by making use of rdma cgroup.
> 
> Resource limit enforcement is hierarchical.
> 
> When process is migrated with active RDMA resources, rdma cgroup
> continues to uncharge original cgroup for allocated resource. New resource
> is charged to current process's cgroup, which means if the process is
> migrated with active resources, for new resources it will be charged to
> new cgroup and old resources will be correctly uncharged from old cgroup.
> 
> Changes from v10:
>   * (To address comments from Tejun, Christoph)
>    1. Removed unused rpool_list_lock from rdma_cgroup structure.
>    2. Moved rdma resource definition to rdma cgroup instead of IB stack
>    3. Added prefix rdmacg to static instances
>    4. Simplified locking with single mutex for all operations
>    5. Following approach of atomically allocating object and
>       charging resource in hirerchy
>    6. Code simplification due to single lock
>    7. Using for_each_set_bit API for bit operation
>    8. Renamed list heads as Objects instead of _head
>    9. Renamed list entries as _node instead of _list.
>   10. Made usage_num to 64 bit to avoid overflow and to avoid 
>       additional code to track non zero number of usage counts.
>   * (To address comments from Doug)
>    1. Added copyright and GPLv2 license

Looks good to me.  I just have a nit in the documentation.  Christoph,
what do you think?

Thanks.

-- 
tejun