Re: [PATCHv6 1/3] rdmacg: Added rdma cgroup controller

[Haggai Eran]

On 25/02/2016 15:34, Parav Pandit wrote:
> On Thu, Feb 25, 2016 at 5:33 PM, Haggai Eran  wrote:
> +retry:
> + spin_lock(>rpool_list_lock);
> + rpool = find_cg_rpool_locked(cg, device);
> + if (!rpool) {
> + spin_unlock(>rpool_list_lock);
> + ret = alloc_cg_rpool(cg, device);
> + if (ret)
> + goto err;
> + else
> + goto retry;
 Instead of retrying after allocation of a new rpool, why not just return 
 the
 newly allocated rpool (or the existing one) from alloc_cg_rpool?
>>>
>>> It can be done, but locking semantics just becomes difficult to
>>> review/maintain with that where alloc_cg_rpool will unlock and lock
>>> conditionally later on.
>> Maybe I'm missing something, but couldn't you simply lock rpool_list_lock
>> inside alloc_cg_rpool()? It already does that around its call to
>> find_cg_rpool_locked() and the insertion to cg_list.
> 
> No. ref_count and usage counters are updated at level where lock is
> taken in charge_cg_resource().
> If I move locking rpool_list_lock inside alloc_cg_rpool, unlocking
> will continue outside, alloc_cg_rpool() when its found or allocated.
> As you acknowledged in below comment that this makes confusing to
> lock/unlock from different context, I think current implementation
> achieves both.
> (a) take lock from single context
> (b) keep functionality of find and alloc in two separate individual functions

Okay, fair enough.

>> I thought that was about functions that only locked the lock, called the
>> find function, and released the lock. What I'm suggesting is to have one
>> function that does "lock + find + allocate if needed + unlock",
> 
> I had similar function in past which does,
> "lock + find + allocate if needed + + inc_ref_cnt + unlock", (get_cg_rpool)
> update usage_counter atomically, because other thread/process might update 
> too.
> check atomic_dec_cnt - on reaching zero, "lock + del_entry + unlock + free".
> 
> Tejun asked to simplify this to,
> 
> "lock + find + allocate if needed + inc_ref_cnt_without_atomic" + unlock".
> which I did in this patch v6.

Okay.

>> and another
>> function that does (under caller's lock) "check ref count + check max count +
>> release rpool".
> This can be done. Have one dumb basic question for thiat.
> Can we call kfree() with spin_lock held? All these years I tend to
> avoid doing so.
> 

I think so. This is an old link but I think it still applies: 
https://lkml.org/lkml/2004/11/21/130
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Re: [PATCHv6 1/3] rdmacg: Added rdma cgroup controller

[Parav Pandit]

> Can we call kfree() with spin_lock held? All these years I tend to
> avoid doing so.
Also it doesn't look correct to hold the lock while freeing the memory
which is totally unrelated to the lock.
With that I think current code appears ok with exception that its
duplicated at two place for code readability around lock.
What say?
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Re: [PATCHv6 1/3] rdmacg: Added rdma cgroup controller

[Parav Pandit]

On Thu, Feb 25, 2016 at 5:33 PM, Haggai Eran  wrote:
 +retry:
 + spin_lock(>rpool_list_lock);
 + rpool = find_cg_rpool_locked(cg, device);
 + if (!rpool) {
 + spin_unlock(>rpool_list_lock);
 + ret = alloc_cg_rpool(cg, device);
 + if (ret)
 + goto err;
 + else
 + goto retry;
>>> Instead of retrying after allocation of a new rpool, why not just return the
>>> newly allocated rpool (or the existing one) from alloc_cg_rpool?
>>
>> It can be done, but locking semantics just becomes difficult to
>> review/maintain with that where alloc_cg_rpool will unlock and lock
>> conditionally later on.
> Maybe I'm missing something, but couldn't you simply lock rpool_list_lock
> inside alloc_cg_rpool()? It already does that around its call to
> find_cg_rpool_locked() and the insertion to cg_list.

No. ref_count and usage counters are updated at level where lock is
taken in charge_cg_resource().
If I move locking rpool_list_lock inside alloc_cg_rpool, unlocking
will continue outside, alloc_cg_rpool() when its found or allocated.
As you acknowledged in below comment that this makes confusing to
lock/unlock from different context, I think current implementation
achieves both.
(a) take lock from single context
(b) keep functionality of find and alloc in two separate individual functions

>
>> This path will be hit anyway on first allocation typically. Once
>> application is warm up, it will be unlikely to enter here.
>> I should change if(!rpool) to if (unlikely(!rpool)).
> Theoretically the new allocated rpool can be released again by the time you
> get to the second call to find_cg_rpool_locked().
>
Thats ok, because if that occurs find_cg_rpool_locked() won't find the
entry and will try to allocate again.
Things work fine in that case.

> I thought that was about functions that only locked the lock, called the
> find function, and released the lock. What I'm suggesting is to have one
> function that does "lock + find + allocate if needed + unlock",

I had similar function in past which does,
"lock + find + allocate if needed + + inc_ref_cnt + unlock", (get_cg_rpool)
update usage_counter atomically, because other thread/process might update too.
check atomic_dec_cnt - on reaching zero, "lock + del_entry + unlock + free".

Tejun asked to simplify this to,

"lock + find + allocate if needed + inc_ref_cnt_without_atomic" + unlock".
which I did in this patch v6.

> and another
> function that does (under caller's lock) "check ref count + check max count +
> release rpool".
This can be done. Have one dumb basic question for thiat.
Can we call kfree() with spin_lock held? All these years I tend to
avoid doing so.
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Re: [PATCHv6 1/3] rdmacg: Added rdma cgroup controller

[Haggai Eran]

On 24/02/2016 18:16, Parav Pandit wrote:
>>> + struct rdmacg_resource_pool *rpool;
>>> + struct rdmacg_pool_info *pool_info = >pool_info;
>>> +
>>> + spin_lock(>rpool_list_lock);
>>> + rpool = find_cg_rpool_locked(cg, device);
>> Is it possible for rpool to be NULL?
>>
> Unlikely, unless we have but in cgroup implementation.
> It may be worth to add WARN_ON and return from here to avoid kernel crash.
Sounds good.

>>> +static int charge_cg_resource(struct rdma_cgroup *cg,
>>> +   struct rdmacg_device *device,
>>> +   int index, int num)
>>> +{
>>> + struct rdmacg_resource_pool *rpool;
>>> + s64 new;
>>> + int ret = 0;
>>> +
>>> +retry:
>>> + spin_lock(>rpool_list_lock);
>>> + rpool = find_cg_rpool_locked(cg, device);
>>> + if (!rpool) {
>>> + spin_unlock(>rpool_list_lock);
>>> + ret = alloc_cg_rpool(cg, device);
>>> + if (ret)
>>> + goto err;
>>> + else
>>> + goto retry;
>> Instead of retrying after allocation of a new rpool, why not just return the
>> newly allocated rpool (or the existing one) from alloc_cg_rpool?
> 
> It can be done, but locking semantics just becomes difficult to
> review/maintain with that where alloc_cg_rpool will unlock and lock
> conditionally later on.
Maybe I'm missing something, but couldn't you simply lock rpool_list_lock
inside alloc_cg_rpool()? It already does that around its call to 
find_cg_rpool_locked() and the insertion to cg_list.

> This path will be hit anyway on first allocation typically. Once
> application is warm up, it will be unlikely to enter here.
> I should change if(!rpool) to if (unlikely(!rpool)).
Theoretically the new allocated rpool can be released again by the time you
get to the second call to find_cg_rpool_locked().

>>> + spin_lock(>rpool_list_lock);
>>> + rpool = find_cg_rpool_locked(cg, device);
>>> + if (!rpool) {
>>> + spin_unlock(>rpool_list_lock);
>>> + ret = alloc_cg_rpool(cg, device);
>>> + if (ret)
>>> + goto opt_err;
>>> + else
>>> + goto retry;
>> You can avoid the retry here too. Perhaps this can go into a function.
>>
> In v5 I had wrapper around code which used to similar hiding using
> get_cg_rpool and put_cg_rpool helper functions.
> But Tejun was of opinion that I should have locks outside of all those
> functions. With that approach, this is done.
> So I think its ok. to have it this way.
I thought that was about functions that only locked the lock, called the 
find function, and released the lock. What I'm suggesting is to have one
function that does "lock + find + allocate if needed + unlock", and another
function that does (under caller's lock) "check ref count + check max count +
release rpool".

>>> + }
>>> +
>>> + /* now set the new limits of the rpool */
>>> + while (enables) {
>>> + /* if user set the limit, enables bit is set */
>>> + if (enables & BIT(i)) {
>>> + enables &= ~BIT(i);
>>> + set_resource_limit(rpool, i, new_limits[i]);
>>> + }
>>> + i++;
>>> + }
>>> + if (rpool->refcnt == 0 &&
>>> + rpool->num_max_cnt == pool_info->table_len) {
>>> + /*
>>> +  * No user of the rpool and all entries are
>>> +  * set to max, so safe to delete this rpool.
>>> +  */
>>> + list_del(>cg_list);
>>> + spin_unlock(>rpool_list_lock);
>>> + free_cg_rpool(rpool);
>>> + } else {
>>> + spin_unlock(>rpool_list_lock);
>>> + }
>> You should consider putting this piece of code in a function (the
>> check of the reference counts and release of the rpool).
>>
> Yes. I did. Same as above comment. Also this function will have to
> unlock. Its usually better to lock/unlock from same function level,
> instead of locking at one level and unlocking from inside the
> function.
> Or
> I should have
> cg_rpool_cond_free_unlock() for above code (check of the reference
> counts and release of the rpool)?
It is confusing to lock and unlock in different contexts. Why not lock
in the caller context? free_cg_rpool() can be called under rpool_list_lock,
couldn't it? It locks device->rpool_lock, but uncharge_cg_resource() also
locks both in the same order.

Thanks,
Haggai
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Re: [PATCHv6 1/3] rdmacg: Added rdma cgroup controller

[Haggai Eran]

Hi,

Overall I the patch looks good to me. I have a few comments below.

On 20/02/2016 13:00, Parav Pandit wrote:
> Resource pool is created/destroyed dynamically whenever
> charging/uncharging occurs respectively and whenever user
> configuration is done. Its a tradeoff of memory vs little more code
Its -> It's
> space that creates resource pool whenever necessary,
> instead of creating them during cgroup creation and device registration
> time.
> 
> Signed-off-by: Parav Pandit 

> diff --git a/include/linux/cgroup_rdma.h b/include/linux/cgroup_rdma.h
> new file mode 100644
> index 000..b370733
> --- /dev/null
> +++ b/include/linux/cgroup_rdma.h

> +struct rdmacg_device {
> + struct rdmacg_pool_info pool_info;
> + struct list_headrdmacg_list;
> + struct list_headrpool_head;
> + spinlock_t  rpool_lock; /* protects rsource pool list */
rsource -> resource

> + char*name;
> +};
> +
> +/* APIs for RDMA/IB stack to publish when a device wants to
> + * participate in resource accounting
> + */
> +int rdmacg_register_device(struct rdmacg_device *device);
> +void rdmacg_unregister_device(struct rdmacg_device *device);
> +
> +/* APIs for RDMA/IB stack to charge/uncharge pool specific resources */
> +int rdmacg_try_charge(struct rdma_cgroup **rdmacg,
> +   struct rdmacg_device *device,
> +   int resource_index,
> +   int num);
> +void rdmacg_uncharge(struct rdma_cgroup *cg,
> +  struct rdmacg_device *device,
> +  int resource_index,
> +  int num);
> +void rdmacg_query_limit(struct rdmacg_device *device,
> + int *limits, int max_count);
You can drop the max_count parameter, and require the caller to
always provide pool_info->table_len items, couldn't you?

> +
> +#endif   /* CONFIG_CGROUP_RDMA */
> +#endif   /* _CGROUP_RDMA_H */
> diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
> index 0df0336a..d0e597c 100644
> --- a/include/linux/cgroup_subsys.h
> +++ b/include/linux/cgroup_subsys.h
> @@ -56,6 +56,10 @@ SUBSYS(hugetlb)
>  SUBSYS(pids)
>  #endif
>  
> +#if IS_ENABLED(CONFIG_CGROUP_RDMA)
> +SUBSYS(rdma)
> +#endif
> +
>  /*
>   * The following subsystems are not supported on the default hierarchy.
>   */
> diff --git a/init/Kconfig b/init/Kconfig
> index 2232080..1741b65 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1054,6 +1054,16 @@ config CGROUP_PIDS
> since the PIDs limit only affects a process's ability to fork, not to
> attach to a cgroup.
>  
> +config CGROUP_RDMA
> + bool "RDMA controller"
> + help
> +   Provides enforcement of RDMA resources defined by IB stack.
> +   It is fairly easy for consumers to exhaust RDMA resources, which
> +   can result into resource unavailibility to other consumers.
unavailibility -> unavailability
> +   RDMA controller is designed to stop this from happening.
> +   Attaching processes with active RDMA resources to the cgroup
> +   hierarchy is allowed even if can cross the hierarchy's limit.
> +
>  config CGROUP_FREEZER
>   bool "Freezer controller"
>   help
> diff --git a/kernel/Makefile b/kernel/Makefile
> index baa55e5..501f5df 100644

> +/**
> + * uncharge_cg_resource - uncharge resource for rdma cgroup
> + * @cg: pointer to cg to uncharge and all parents in hierarchy
It only uncharges a single cg, right?
> + * @device: pointer to ib device
> + * @index: index of the resource to uncharge in cg (resource pool)
> + * @num: the number of rdma resource to uncharge
> + *
> + * It also frees the resource pool in the hierarchy for the resource pool
> + * which was created as part of charing operation.
charing -> charging
> + */
> +static void uncharge_cg_resource(struct rdma_cgroup *cg,
> +  struct rdmacg_device *device,
> +  int index, int num)
> +{
> + struct rdmacg_resource_pool *rpool;
> + struct rdmacg_pool_info *pool_info = >pool_info;
> +
> + spin_lock(>rpool_list_lock);
> + rpool = find_cg_rpool_locked(cg, device);
Is it possible for rpool to be NULL?

> +
> + /*
> +  * A negative count (or overflow) is invalid,
> +  * it indicates a bug in the rdma controller.
> +  */
> + rpool->resources[index].usage -= num;
> +
> + WARN_ON_ONCE(rpool->resources[index].usage < 0);
> + rpool->refcnt--;
> + if (rpool->refcnt == 0 && rpool->num_max_cnt == pool_info->table_len) {
> + /*
> +  * No user of the rpool and all entries are set to max, so
> +  * safe to delete this rpool.
> +  */
> + list_del(>cg_list);
> + spin_unlock(>rpool_list_lock);
> +
> + free_cg_rpool(rpool);
> + return;
> + }
> + spin_unlock(>rpool_list_lock);
> +}

> +/**
> + * charge_cg_resource - charge 

Re: [PATCHv6 1/3] rdmacg: Added rdma cgroup controller

[Leon Romanovsky]

On Sat, Feb 20, 2016 at 04:30:04PM +0530, Parav Pandit wrote:
> Added rdma cgroup controller that does accounting, limit enforcement
> on rdma/IB verbs and hw resources.
> 
> Added rdma cgroup header file which defines its APIs to perform
> charing/uncharing functionality and device registration which will
> participate in controller functions of accounting and limit
> enforcements. It also define rdmacg_device structure to bind IB stack
> and RDMA cgroup controller.
> 
> RDMA resources are tracked using resource pool. Resource pool is per
> device, per cgroup entity which allows setting up accounting limits
> on per device basis.
> 
> Resources are not defined by the RDMA cgroup, instead they are defined
> by the external module IB stack. This allows extending IB stack
> without changing kernel, as IB stack is going through changes
> and enhancements.
> 
> Resource pool is created/destroyed dynamically whenever
> charging/uncharging occurs respectively and whenever user
> configuration is done. Its a tradeoff of memory vs little more code
> space that creates resource pool whenever necessary,
> instead of creating them during cgroup creation and device registration
> time.
> 
> Signed-off-by: Parav Pandit 
> ---
>  include/linux/cgroup_rdma.h   |  53 +++
>  include/linux/cgroup_subsys.h |   4 +
>  init/Kconfig  |  10 +
>  kernel/Makefile   |   1 +
>  kernel/cgroup_rdma.c  | 753 
> ++
>  5 files changed, 821 insertions(+)
>  create mode 100644 include/linux/cgroup_rdma.h
>  create mode 100644 kernel/cgroup_rdma.c
> 
> diff --git a/include/linux/cgroup_rdma.h b/include/linux/cgroup_rdma.h
> new file mode 100644
> index 000..b370733
> --- /dev/null
> +++ b/include/linux/cgroup_rdma.h
> @@ -0,0 +1,53 @@
> +#ifndef _CGROUP_RDMA_H
> +#define _CGROUP_RDMA_H
> +
> +#include 
> +
> +struct rdma_cgroup {
> +#ifdef CONFIG_CGROUP_RDMA
> + struct cgroup_subsys_state  css;
> +
> + spinlock_t rpool_list_lock; /* protects resource pool list */
> + struct list_head rpool_head;/* head to keep track of all resource
> +  * pools that belongs to this cgroup.
> +  */
> +#endif
> +};
> +
> +#ifdef CONFIG_CGROUP_RDMA

I'm sure that you already asked about that, but why do you need ifdef
embedded in struct rdma_cgroup and right after that the same one?
Can you place this ifdef before declaring struct rdma_cgroup?

> +
> +struct rdmacg_device;
> +

Thanks
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Re: [PATCHv6 1/3] rdmacg: Added rdma cgroup controller

[Parav Pandit]

On Sun, Feb 21, 2016 at 8:39 PM, Leon Romanovsky  wrote:
> On Sun, Feb 21, 2016 at 07:41:08PM +0530, Parav Pandit wrote:
>> CONFIG_CGROUP_RDMA
>>
>> On Sun, Feb 21, 2016 at 7:15 PM, Leon Romanovsky  wrote:
>> > On Sun, Feb 21, 2016 at 05:03:05PM +0530, Parav Pandit wrote:
>> >> On Sun, Feb 21, 2016 at 1:13 PM, Leon Romanovsky  wrote:
>> >> > On Sat, Feb 20, 2016 at 04:30:04PM +0530, Parav Pandit wrote:
>> >> > Can you place this ifdef before declaring struct rdma_cgroup?
>> >> Yes. I missed out this cleanup. Done locally now.
>> >
>> > Great, additional thing which spotted my attention was related to
>> > declaring and using the new cgroups functions. There are number of
>> > places where you protected the calls by specific ifdefs in the
>> > IB/core c-files and not in h-files as it is usually done.
>> >
>> ib_device_register_rdmacg, ib_device_unregister_rdmacg are the only
>> two functions called from IB/core as its tied to functionality.
>> They can also be implemented as NULL call when CONFIG_CGROUP_RDMA is 
>> undefined.
>> (Similar to ib_rdmacg_try_charge and others).
>> I didn't do because occurrence of call of register and unregister is
>> limited to single file and only twice compare to charge/uncharge
>> functions.
>> Either way is fine with me, I can make the changes which you
>> described. Let me know.
>
> Please do,
> IMHO, it is better to have one place which handles all relevant ifdefs
> and functions. IB/core doesn't need to know about cgroups implementation.
>
ok. Done. Thanks for the review. I will accumulate more comments from
Tejun and others before spinning v7.
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Re: [PATCHv6 1/3] rdmacg: Added rdma cgroup controller

[Leon Romanovsky]

On Sun, Feb 21, 2016 at 07:41:08PM +0530, Parav Pandit wrote:
> CONFIG_CGROUP_RDMA
> 
> On Sun, Feb 21, 2016 at 7:15 PM, Leon Romanovsky  wrote:
> > On Sun, Feb 21, 2016 at 05:03:05PM +0530, Parav Pandit wrote:
> >> On Sun, Feb 21, 2016 at 1:13 PM, Leon Romanovsky  wrote:
> >> > On Sat, Feb 20, 2016 at 04:30:04PM +0530, Parav Pandit wrote:
> >> > Can you place this ifdef before declaring struct rdma_cgroup?
> >> Yes. I missed out this cleanup. Done locally now.
> >
> > Great, additional thing which spotted my attention was related to
> > declaring and using the new cgroups functions. There are number of
> > places where you protected the calls by specific ifdefs in the
> > IB/core c-files and not in h-files as it is usually done.
> >
> ib_device_register_rdmacg, ib_device_unregister_rdmacg are the only
> two functions called from IB/core as its tied to functionality.
> They can also be implemented as NULL call when CONFIG_CGROUP_RDMA is 
> undefined.
> (Similar to ib_rdmacg_try_charge and others).
> I didn't do because occurrence of call of register and unregister is
> limited to single file and only twice compare to charge/uncharge
> functions.
> Either way is fine with me, I can make the changes which you
> described. Let me know.

Please do,
IMHO, it is better to have one place which handles all relevant ifdefs
and functions. IB/core doesn't need to know about cgroups implementation.

Thanks
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[PATCHv6 1/3] rdmacg: Added rdma cgroup controller

[Parav Pandit]

Added rdma cgroup controller that does accounting, limit enforcement
on rdma/IB verbs and hw resources.

Added rdma cgroup header file which defines its APIs to perform
charing/uncharing functionality and device registration which will
participate in controller functions of accounting and limit
enforcements. It also define rdmacg_device structure to bind IB stack
and RDMA cgroup controller.

RDMA resources are tracked using resource pool. Resource pool is per
device, per cgroup entity which allows setting up accounting limits
on per device basis.

Resources are not defined by the RDMA cgroup, instead they are defined
by the external module IB stack. This allows extending IB stack
without changing kernel, as IB stack is going through changes
and enhancements.

Resource pool is created/destroyed dynamically whenever
charging/uncharging occurs respectively and whenever user
configuration is done. Its a tradeoff of memory vs little more code
space that creates resource pool whenever necessary,
instead of creating them during cgroup creation and device registration
time.

Signed-off-by: Parav Pandit 
---
 include/linux/cgroup_rdma.h   |  53 +++
 include/linux/cgroup_subsys.h |   4 +
 init/Kconfig  |  10 +
 kernel/Makefile   |   1 +
 kernel/cgroup_rdma.c  | 753 ++
 5 files changed, 821 insertions(+)
 create mode 100644 include/linux/cgroup_rdma.h
 create mode 100644 kernel/cgroup_rdma.c

diff --git a/include/linux/cgroup_rdma.h b/include/linux/cgroup_rdma.h
new file mode 100644
index 000..b370733
--- /dev/null
+++ b/include/linux/cgroup_rdma.h
@@ -0,0 +1,53 @@
+#ifndef _CGROUP_RDMA_H
+#define _CGROUP_RDMA_H
+
+#include 
+
+struct rdma_cgroup {
+#ifdef CONFIG_CGROUP_RDMA
+   struct cgroup_subsys_state  css;
+
+   spinlock_t rpool_list_lock; /* protects resource pool list */
+   struct list_head rpool_head;/* head to keep track of all resource
+* pools that belongs to this cgroup.
+*/
+#endif
+};
+
+#ifdef CONFIG_CGROUP_RDMA
+
+struct rdmacg_device;
+
+struct rdmacg_pool_info {
+   const char **resource_name_table;
+   int table_len;
+};
+
+struct rdmacg_device {
+   struct rdmacg_pool_info pool_info;
+   struct list_headrdmacg_list;
+   struct list_headrpool_head;
+   spinlock_t  rpool_lock; /* protects rsource pool list */
+   char*name;
+};
+
+/* APIs for RDMA/IB stack to publish when a device wants to
+ * participate in resource accounting
+ */
+int rdmacg_register_device(struct rdmacg_device *device);
+void rdmacg_unregister_device(struct rdmacg_device *device);
+
+/* APIs for RDMA/IB stack to charge/uncharge pool specific resources */
+int rdmacg_try_charge(struct rdma_cgroup **rdmacg,
+ struct rdmacg_device *device,
+ int resource_index,
+ int num);
+void rdmacg_uncharge(struct rdma_cgroup *cg,
+struct rdmacg_device *device,
+int resource_index,
+int num);
+void rdmacg_query_limit(struct rdmacg_device *device,
+   int *limits, int max_count);
+
+#endif /* CONFIG_CGROUP_RDMA */
+#endif /* _CGROUP_RDMA_H */
diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
index 0df0336a..d0e597c 100644
--- a/include/linux/cgroup_subsys.h
+++ b/include/linux/cgroup_subsys.h
@@ -56,6 +56,10 @@ SUBSYS(hugetlb)
 SUBSYS(pids)
 #endif
 
+#if IS_ENABLED(CONFIG_CGROUP_RDMA)
+SUBSYS(rdma)
+#endif
+
 /*
  * The following subsystems are not supported on the default hierarchy.
  */
diff --git a/init/Kconfig b/init/Kconfig
index 2232080..1741b65 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1054,6 +1054,16 @@ config CGROUP_PIDS
  since the PIDs limit only affects a process's ability to fork, not to
  attach to a cgroup.
 
+config CGROUP_RDMA
+   bool "RDMA controller"
+   help
+ Provides enforcement of RDMA resources defined by IB stack.
+ It is fairly easy for consumers to exhaust RDMA resources, which
+ can result into resource unavailibility to other consumers.
+ RDMA controller is designed to stop this from happening.
+ Attaching processes with active RDMA resources to the cgroup
+ hierarchy is allowed even if can cross the hierarchy's limit.
+
 config CGROUP_FREEZER
bool "Freezer controller"
help
diff --git a/kernel/Makefile b/kernel/Makefile
index baa55e5..501f5df 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -56,6 +56,7 @@ obj-$(CONFIG_COMPAT) += compat.o
 obj-$(CONFIG_CGROUPS) += cgroup.o
 obj-$(CONFIG_CGROUP_FREEZER) += cgroup_freezer.o
 obj-$(CONFIG_CGROUP_PIDS) += cgroup_pids.o
+obj-$(CONFIG_CGROUP_RDMA) += cgroup_rdma.o
 obj-$(CONFIG_CPUSETS) += cpuset.o
 obj-$(CONFIG_UTS_NS) +=