linux-kernel - Re: [PATCH 0/7] devcg: device cgroup extension for rdma resource

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Date:	Wed, 28 Oct 2015 13:44:12 +0530
From:	Parav Pandit <pandit.parav@...il.com>
To:	Haggai Eran <haggaie@...lanox.com>
Cc:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	"Hefty, Sean" <sean.hefty@...el.com>, Tejun Heo <tj@...nel.org>,
	Doug Ledford <dledford@...hat.com>,
	"cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	"lizefan@...wei.com" <lizefan@...wei.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Jonathan Corbet <corbet@....net>,
	"james.l.morris@...cle.com" <james.l.morris@...cle.com>,
	"serge@...lyn.com" <serge@...lyn.com>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Matan Barak <matanb@...lanox.com>,
	"raindel@...lanox.com" <raindel@...lanox.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-security-module@...r.kernel.org" 
	<linux-security-module@...r.kernel.org>
Subject: Re: [PATCH 0/7] devcg: device cgroup extension for rdma resource

Hi,

I finally got some chance and progress on redesigning rdma cgroup
controller for the most use cases that we discussed in this email
chain.
I am posting RFC and soon code in new email.

Parav


On Sun, Sep 20, 2015 at 4:05 PM, Haggai Eran <haggaie@...lanox.com> wrote:
> On 15/09/2015 06:45, Jason Gunthorpe wrote:
>> No, I'm saying the resource pool is *well defined* and *fixed* by each
>> hardware.
>>
>> The only question is how do we expose the N resource limits, the list
>> of which is totally vendor specific.
>
> I don't see why you say the limits are vendor specific. It is true that
> different RDMA devices have different implementations and capabilities,
> but they all use the expose the same set of RDMA objects with their
> limitations. Whether those limitations come from hardware limitations,
> from the driver, or just because the address space is limited, they can
> still be exhausted.
>
>> Yes, using a % scheme fixes the ratios, 1% is going to be a certain
>> number of PD's, QP's, MRs, CQ's, etc at a ratio fixed by the driver
>> configuration. That is the trade off for API simplicity.
>>
>>
>> Yes, this results in some resources being over provisioned.
>
> I agree that such a scheme will be easy to configure, but I don't think
> it can work well in all situations. Imagine you want to let one
> container use almost all RC QPs as you want it to connect to the entire
> cluster through RC. Other containers can still use a single datagram QP
> to connect to the entire cluster, but they would require many address
> handles. If you force a fixed ratio of resources given to each container
> it would be hard to describe such a partitioning.
>
> I think it would be better to expose different controls for the
> different RDMA resources.
>
> Regards,
> Haggai
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