netdev - Re: [RFC] RESEND - rdmatool

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Message-ID: <20170119191257.GA28570@mtr-leonro.local>
Date:   Thu, 19 Jan 2017 21:12:57 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:     Bart Van Assche <bart.vanassche@...disk.com>,
        Or Gerlitz <gerlitz.or@...il.com>,
        Ariel Almog <arielalmogworkemails@...il.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [RFC] RESEND - rdmatool - tool for RDMA users

On Thu, Jan 19, 2017 at 11:03:08AM -0700, Jason Gunthorpe wrote:
> On Thu, Jan 19, 2017 at 08:33:26AM +0200, Leon Romanovsky wrote:
> > On Wed, Jan 18, 2017 at 01:45:14PM -0800, Bart Van Assche wrote:
> > > On 01/18/2017 10:31 AM, Jason Gunthorpe wrote:
> > > > I think it depends on what this tool is supposed to cover, but based
> > > > on the description, I would start with netlink-only.
> > > >
> > > > The only place verbs covers a similar ground is in 'device
> > > > capabilities' - for some of that you might want to open a new-uAPI
> > > > verbs fd, but even the capability data from that would not be
> > > > totally offensive to be accessed over netlink.
> > > >
> > > > IMHO netlink should cover almost everything found in sysfs today.
> > >
> > > We would need a very strong argument to introduce a netlink API that
> > > duplicates existing sysfs API functionality. Since the sysfs API is
> > > extensible, why not extend that API further? E.g. the SCST sysfs API
> > > shows that more is possible with sysfs than what most kernel drivers
> > > realize.
> >
> > We didn't look deeply on sysfs mainly because it is unpopular
> > in netdev community. Maybe we were misled and it is simply not true.
>
> sysfs is unpopular because the 'one value per file' dogma is laregly
> unsuitable for complex mulit-value atomic changes which are common in
> netdev. You can force it to work, but it is pretty horrible..
>
> It is also very expensive if you want to shuttle a lot of data, eg I
> could not see doing something like 'netstat' for IB through sysfs
>
> Maybe you should start by showing some examples of command out you
> wish to have in a rdmatool ..

Ariel wrote very simplified version in his proposal:
Functionality
*************
The rdmatool will provide a platform which can grow as needed. The
initial functionality might include:
* help – man page
* version – version number
* statistics – RDMA statistics – such as port and QP statistics
  	       To allow easy reading of statistics, we offer to use a filter
  	       functionality, allowing reading of statistics families, such
	       as link layer, error counters, etc.
* protocol – RoCE/iWARP/InfiniBand related configuration, such as RDMA
	     congestion configuration and statistics
* query – RDMA objects (qp, cq, srq, ..) information such as owner,
	  status, type
* debug – an interface to allow read and write from user space
	  to the provider RDMA driver, exposing debug information.

Commands similar to "ip" program.

>
> Jason

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