linux-kernel - Re: [PATCHv12 1/3] rdmacg: Added rdma cgroup controller

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Date:   Wed, 14 Sep 2016 14:49:56 +0530
From:   Parav Pandit <pandit.parav@...il.com>
To:     Matan Barak <matanb@...lanox.com>
Cc:     Leon Romanovsky <leon@...nel.org>,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        Christoph Hellwig <hch@....de>, Tejun Heo <tj@...nel.org>,
        cgroups@...r.kernel.org, linux-doc@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-rdma@...r.kernel.org, Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Doug Ledford <dledford@...hat.com>,
        Liran Liss <liranl@...lanox.com>,
        "Hefty, Sean" <sean.hefty@...el.com>,
        Haggai Eran <haggaie@...lanox.com>,
        Jonathan Corbet <corbet@....net>, james.l.morris@...cle.com,
        serge@...lyn.com, Or Gerlitz <ogerlitz@...lanox.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-security-module@...r.kernel.org
Subject: Re: [PATCHv12 1/3] rdmacg: Added rdma cgroup controller

Hi Matan,

On Wed, Sep 14, 2016 at 1:44 PM, Matan Barak <matanb@...lanox.com> wrote:
> On 14/09/2016 10:06, Parav Pandit wrote:
>>
>> Hi Dennis,
>>
>> Do you know how would HFI1 driver would work along with rdma cgroup?
>>
>> Hi Matan, Leon, Jason,
>> Apart from HFI1, is there any other concern?
>
>
> I just wonder how things like RSS will work. For example, a RSS QP doesn't
> really have a queue (if I recall, it's connected to work queues via an
> indirection table). So, when a user creates such a QP, do you want to
> account it as a regular QP?
> How are work queues accounted?

ib_create_rwq_ind_table verb allows creating indirection table.
I assume it allows creating multiple such tables.
If it is so, than number of tables should be a cgroup resource that we
can add in follow on patch.
By doing so, one container doesn't takeaway all the tables.

>
>
>> Or Patch is good to go?
>>
>> 4.8 dates are close by (2 weeks) and there are two git trees involved
>> (that might cause merge error to Linus) so if there are no issues, I
>> would like to make request to Doug to consider it for 4.8 early on.
>>
>> Parav
>>
>> On Mon, Sep 12, 2016 at 10:37 AM, Leon Romanovsky <leon@...nel.org> wrote:
>>>
>>> On Sun, Sep 11, 2016 at 11:52:35AM -0600, Jason Gunthorpe wrote:
>>>>
>>>> On Sun, Sep 11, 2016 at 07:24:45PM +0200, Christoph Hellwig wrote:
>>>>>>>>
>>>>>>>> I've posted some initial work toward a) a while ago, and once we
>>>>>>
>>>>>>
>>>>>> Did it get merged? Do you have a pointer?
>>>>>
>>>>>
>>>>> http://www.spinics.net/lists/linux-rdma/msg31958.html
>>>>
>>>>
>>>> Right, I remember that. Certainly the right direction
>>>>
>>>>>> However, everything under verbs is not straightforward. The files in
>>>>>> userspace are not copies...
>>>>>>
>>>>>> user:
>>>>>>
>>>>>> struct ibv_query_device {
>>>>>>        __u32 command;
>>>>>>        __u16 in_words;
>>>>>>        __u16 out_words;
>>>>>>        __u64 response;
>>>>>>        __u64 driver_data[0];
>>>>>> };
>>>>>>
>>>>>> kernel:
>>>>>>
>>>>>> struct ib_uverbs_query_device {
>>>>>>         __u64 response;
>>>>>>         __u64 driver_data[0];
>>>>>> };
>>>>>
>>>>>
>>>>> We'll obviously need different strutures for the libibvers API
>>>>> and the kernel interface in this case, and we'll need to figure out
>>>>> how to properly translate them.  I think a cast, plus compile time
>>>>> type checking ala BUILD_BUG_ON is the way to go.
>>>>
>>>>
>>>> I'm not sure I follow, which would I cast?
>>>>
>>>> BUILD_BUG_ON(sizeof(ibv_query_device) == sizeof(ib_uverbs_cmd_hdr) +
>>>>              sizeof(ib_uverbs_query_device))
>>>>
>>>> ?
>>>>
>>>>>> I'm thinking the best way forward might be to use a script and
>>>>>> transform userspace into:
>>>>>>
>>>>>> struct ibv_query_device {
>>>>>>   struct ib_uverbs_cmd_hdr hdr;
>>>>>>   struct ib_uverbs_query_device cmd;
>>>>>> };
>>>>>
>>>>>
>>>>> That would break the users of the interface.
>>>>
>>>>
>>>> Sorry, I mean doing this inside rdma-plumbing. Since the change is ABI
>>>> identical the modified libibverbs would still be binary compatible
>>>> with all providers but not source compatible. Since all kernel
>>>> supported providers are in rdma-plumbing we can add the '.cmd.' at the
>>>> same time.
>>>>
>>>> The kernel uapi header would stay the same.
>>>>
>>>>> However automatically generating the user ABI from the kernel one
>>>>> might still be a good idea in the long run.
>>>>
>>>>
>>>> My preference would be to try and use the kernel headers directly.
>>>
>>>
>>> I thought the same, especially after realizing that they are almost
>>> copy/paste from the vendor *-abi.h files.
>>>
>>>>
>>>> Jason
>
>