linux-kernel - Re: [RFC PATCH 08/11] IB/Verbs: Use management helper has

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Message-ID: <CAJuTgQUFXLdaj=+6baamUvPHC4Ocj4f_U6Q5WD9UijbaZ3iYLg@mail.gmail.com>
Date:	Fri, 27 Mar 2015 18:35:28 +0100
From:	Yun Wang <yun.wang@...fitbricks.com>
To:	"ira.weiny" <ira.weiny@...el.com>
Cc:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Roland Dreier <roland@...nel.org>,
	Sean Hefty <sean.hefty@...el.com>,
	Hal Rosenstock <hal.rosenstock@...il.com>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-nfs@...r.kernel.org, netdev@...r.kernel.org,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	"David S. Miller" <davem@...emloft.net>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Moni Shoua <monis@...lanox.com>,
	PJ Waskiewicz <pj.waskiewicz@...idfire.com>,
	Tatyana Nikolova <Tatyana.E.Nikolova@...el.com>,
	Yan Burman <yanb@...lanox.com>,
	Jack Morgenstein <jackm@....mellanox.co.il>,
	Bart Van Assche <bvanassche@....org>,
	Yann Droneaud <ydroneaud@...eya.com>,
	Colin Ian King <colin.king@...onical.com>,
	Majd Dibbiny <majd@...lanox.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Matan Barak <matanb@...lanox.com>,
	Alex Estrin <alex.estrin@...el.com>,
	Doug Ledford <dledford@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Erez Shitrit <erezsh@...lanox.com>,
	Sagi Grimberg <sagig@...lanox.com>,
	Haggai Eran <haggaie@...lanox.com>,
	Shachar Raindel <raindel@...lanox.com>,
	Mike Marciniszyn <mike.marciniszyn@...el.com>,
	Steve Wise <swise@...ngridcomputing.com>,
	Tom Tucker <tom@....us>, Chuck Lever <chuck.lever@...cle.com>
Subject: Re: [RFC PATCH 08/11] IB/Verbs: Use management helper has_iwarp()
 for, iwarp-check

On Fri, Mar 27, 2015 at 6:16 PM, ira.weiny <ira.weiny@...el.com> wrote:
> On Fri, Mar 27, 2015 at 10:13:19AM -0600, Jason Gunthorpe wrote:
>> On Fri, Mar 27, 2015 at 04:47:36PM +0100, Michael Wang wrote:
>> >
>> > Introduce helper has_iwarp() to help us check if an IB device
>> > support IWARP protocol.
>>
>> Should probably be !has_rdma_read_sges()
>>
>> True if the device can handle more than one SGE entry on a RDMA READ
>> work request.
>
> Isn't this value already provided by the query_device verb?
>
> The verbs spec states the Query HCA contains the:
>
> "Maximum number of scatter/gather entries per Work Request supported by the
> HCA."

I'm not sure but may be query_device() is just too expensive for this path?
I need some investigation here too.

Regards,
Michael Wang

>
> -- Ira
>
>>
>> Jason
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