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Date: Tue, 19 Apr 2016 14:26:08 +0530
Message-ID: <CAG53R5Xt1J9+SBvAFRQOcwvkFzeLMkTZ-7vyBG2BVPYdU8p4Nw@mail.gmail.com>
Subject: Re: [PATCHv10 1/3] rdmacg: Added rdma cgroup controller
From: Parav Pandit <pandit.parav@gmail.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Tejun Heo <tj@kernel.org>, cgroups@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-rdma@vger.kernel.org, lizefan@huawei.com,
        Johannes Weiner <hannes@cmpxchg.org>,
        Doug Ledford <dledford@redhat.com>, Liran Liss <liranl@mellanox.com>,
        "Hefty, Sean" <sean.hefty@intel.com>,
        Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
        Haggai Eran <haggaie@mellanox.com>, Jonathan Corbet <corbet@lwn.net>,
        james.l.morris@oracle.com, serge@hallyn.com,
        Or Gerlitz <ogerlitz@mellanox.com>, Matan Barak <matanb@mellanox.com>,
        akpm@linux-foundation.org, linux-security-module@vger.kernel.org
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Hi Christoph,

I was on travel. Sorry for the late inline response and question.

Parav


On Tue, Apr 5, 2016 at 10:57 PM, Christoph Hellwig <hch@infradead.org> wrote:
> On Tue, Apr 05, 2016 at 05:55:26AM -0700, Parav Pandit wrote:
>> Just because we add one more rdma resource, we need to ask someone to
>> upgrade kernel?
>
> Yes.  Just like when you need any other core kernel resource.

By architecture Linux kernel allows
(a) plugin of any new block level IO scheduler as kernel module.
This is much more fundamental resource or functionality than rdma resource.
(b) plugin of any new file system as kernel module.

Changing both in field and out of box can do be more harmful than
defining new rdma resource.

RDMA Resource definition by IB core module is very similar to above
two functionality, where elevator and VFS provides basic support
framework and so rdma cgroup controller here.

So can you please help me understand - which resource did you compare
against in your above comment for "core kernel resource"?
I compared it with similar functionality, flexibility given by (a)
block IO Scheduler and (b) VFS subsystem to implement them as kernel
module.