Message-ID: <551A87D3.2070306@profitbricks.com>
Date: Tue, 31 Mar 2015 13:41:07 +0200
From: Michael Wang <yun.wang@profitbricks.com>
MIME-Version: 1.0
To: Tom Talpey <tom@talpey.com>,
        Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
CC: "ira.weiny" <ira.weiny@intel.com>, Roland Dreier <roland@kernel.org>,
        Sean Hefty <sean.hefty@intel.com>,
        Hal Rosenstock <hal.rosenstock@gmail.com>, linux-rdma@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org,
        netdev@vger.kernel.org, "J. Bruce Fields" <bfields@fieldses.org>,
        Trond Myklebust <trond.myklebust@primarydata.com>,
        "David S. Miller" <davem@davemloft.net>,
        Or Gerlitz <ogerlitz@mellanox.com>, Moni Shoua <monis@mellanox.com>,
        PJ Waskiewicz <pj.waskiewicz@solidfire.com>,
        Tatyana Nikolova <Tatyana.E.Nikolova@intel.com>,
        Yan Burman <yanb@mellanox.com>,
        Jack Morgenstein <jackm@dev.mellanox.co.il>,
        Bart Van Assche <bvanassche@acm.org>,
        Yann Droneaud <ydroneaud@opteya.com>,
        Colin Ian King <colin.king@canonical.com>,
        Majd Dibbiny <majd@mellanox.com>, Jiri Kosina <jkosina@suse.cz>,
        Matan Barak <matanb@mellanox.com>, Alex Estrin <alex.estrin@intel.com>,
        Doug Ledford <dledford@redhat.com>, Eric Dumazet <edumazet@google.com>,
        Erez Shitrit <erezsh@mellanox.com>, Sagi Grimberg <sagig@mellanox.com>,
        Haggai Eran <haggaie@mellanox.com>,
        Shachar Raindel <raindel@mellanox.com>,
        Mike Marciniszyn <mike.marciniszyn@intel.com>,
        Steve Wise <swise@opengridcomputing.com>, Tom Tucker <tom@ogc.us>,
        Chuck Lever <chuck.lever@oracle.com>
Subject: Re: [RFC PATCH 08/11] IB/Verbs: Use management helper has_iwarp()
 for, iwarp-check
References: <551579CA.4030901@profitbricks.com> <55157B98.1060103@profitbricks.com> <20150327161319.GB28412@obsidianresearch.com> <20150327171631.GC27862@phlsvsds.ph.intel.com> <20150327172912.GA28901@obsidianresearch.com> <55196754.5010600@profitbricks.com> <20150330223528.GB27728@obsidianresearch.com> <551A4F24.6090405@profitbricks.com> <551A82D3.70806@talpey.com>
In-Reply-To: <551A82D3.70806@talpey.com>
Content-Type: text/plain; charset=windows-1252
Sender: linux-nfs-owner@vger.kernel.org

Hi, Tom

Thanks for the comments :-)

On 03/31/2015 01:19 PM, Tom Talpey wrote:
> [snip]
>
>>
>> Actually I'm thinking about Doug's idea to use rdma_transport_is_XX()
>> instead of the current basic helper, thus may be use rdma_transport_is_iwarp()
>> in here could be better, since it's actually a feature of iwarp tech
>> that RDMA Read only support one scatter-gather entry.
>
> No, you should expose an attribute to surface the maximum length of
> the remote gather list, which varies by adapter as well as protocol.
> The fact that iWARP is different from IB is not relevant, and conflates
> unrelated properties.

To be confirmed, so your point is that the max-read-sges will be different
even the transport is the same IWRAP, and that depends on the capability
of adapter, correct?

I currently only find this one place where infer max-read-sges from
transport type, it looks more like a special case to me rather than a generic
method we could exposed... and also  not very related with IB management
helper concept IMHO.

Regards,
Michael Wang