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From: Sagi Grimberg <sagig@dev.mellanox.co.il>
To: Bart Van Assche <bvanassche@acm.org>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>
Cc: linux-rdma <linux-rdma@vger.kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	Jens Axboe <axboe@kernel.dk>, Robert Elliott <Elliott@hp.com>,
	Ming Lei <ming.lei@canonical.com>
Subject: Re: [PATCH 8/8] IB/srp: Add multichannel support
Date: Wed, 24 Sep 2014 15:22:35 +0300	[thread overview]
Message-ID: <5422B78B.4000501@dev.mellanox.co.il> (raw)
In-Reply-To: <5421C3DF.5000102@acm.org>

On 9/23/2014 10:02 PM, Bart Van Assche wrote:
> On 23/09/2014 10:32, Sagi Grimberg wrote:
>> On 9/19/2014 4:00 PM, Bart Van Assche wrote:
>>> Improve performance by using multiple RDMA/RC channels per SCSI host
>>> for communicating with an SRP target.
>>>
>>
>> Hey Bart,
>>
>> Since you don't seem to negotiate/declare multichannel with the target,
>> did you test this code with some target implementations other than SCST
>> that happen to be out there?
>>
>> Overall, I think this patch would be easier to review if you also
>> provide a list of logical changes (which obviously are introduced in
>> this patch). Patch 7/8 can use some more information of target-channel
>> relations as well.
>
> Hello Sagi,
>
> That's a good question. So far this patch series has only been tested
> against the SCST SRP target driver. However, as you probably noticed, if
> setting up a second or later RDMA channel fails SRP login is not failed
> but communication proceeds with the number of channels that have been
> established. This mechanism should retain backwards compatibility with
> SRP target systems that do not support multichannel communication.
> However, if the new code for SRP login turns out to be triggering bugs
> in existing SRP target implementations we can still add a blacklist for
> these implementations.

I'm more concerned that a target will accept multichannel and then
starts flipping since that wasn't tested in I don't know when, probably
never...

Since SRP_LOGIN_REQ/RESP has some free bits why not declare it and
activate it when both sides *says* they support it? I'd be much calmer
knowing we're on the safe side on this...

>
> I will provide a more detailed list of logical changes in the second
> version of this patch series.

Thanks,

Plus, I would like to run it on my performance setups. can you point me
to the SCST repo? is multichannel supported in scst trunk?

Sagi.

  reply	other threads:[~2014-09-24 12:22 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-19 12:55 [PATCH RFC 0/8] IB/srp: Add multichannel support Bart Van Assche
2014-09-19 12:56 ` Bart Van Assche
2014-09-19 18:02   ` Sagi Grimberg
2014-09-19 12:57 ` [PATCH 2/8] scsi-mq: Add support for multiple hardware queues Bart Van Assche
     [not found]   ` <541C281E.9090206-HInyCGIudOg@public.gmane.org>
2014-09-19 18:05     ` Sagi Grimberg
2014-09-19 18:11       ` Christoph Hellwig
     [not found]       ` <CAF9gx6JfP2bGyMauB6LzepZP_vKEvrd-sPZc5CRuOrtgQ_UCSw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-09-26 11:08         ` Ming Lei
     [not found]           ` <CACVXFVMiYsW=dszQ6mE-o_L8fEDdkO59vJ5qeHKch5c33K_QXw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-09-26 14:02             ` Bart Van Assche
2014-09-19 12:57 ` [PATCH 3/8] scsi-mq: Pass hctx to low-level SCSI drivers Bart Van Assche
     [not found] ` <541C27BF.6070609-HInyCGIudOg@public.gmane.org>
2014-09-19 12:58   ` [PATCH 4/8] IB/srp: Move ib_destroy_cm_id() call into srp_free_ch_ib() Bart Van Assche
     [not found]     ` <541C285B.5010309-HInyCGIudOg@public.gmane.org>
2014-09-19 18:10       ` Sagi Grimberg
2014-09-19 12:58   ` [PATCH 5/8] IB/srp: Remove stale connection retry mechanism Bart Van Assche
2014-09-19 18:25     ` Sagi Grimberg
     [not found]     ` <541C287D.1050900-HInyCGIudOg@public.gmane.org>
2014-09-20 17:45       ` Or Gerlitz
     [not found]         ` <CAJ3xEMhPKiut4MwZH9F7-T0+u7B6XPuh-FTZpA=Xe4ViAj5UUQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-10-02 10:34           ` Bart Van Assche
     [not found]             ` <542D2A3C.2080009-HInyCGIudOg@public.gmane.org>
2014-10-03  8:51               ` Bart Van Assche
2014-09-19 13:00   ` [PATCH 8/8] IB/srp: Add multichannel support Bart Van Assche
     [not found]     ` <541C28E0.7010705-HInyCGIudOg@public.gmane.org>
2014-09-19 14:28       ` Ming Lei
     [not found]         ` <CACVXFVPzz37J-613NZCfPStUBxf0rLOtz71LJ07PpCxYg5nn+g-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-09-19 15:21           ` Bart Van Assche
     [not found]             ` <541C49EC.6030404-HInyCGIudOg@public.gmane.org>
2014-09-19 15:27               ` Ming Lei
2014-09-19 15:35                 ` Bart Van Assche
2014-09-19 15:38                   ` Jens Axboe
2014-09-19 17:30                     ` Sagi Grimberg
2014-09-19 17:33                       ` Jens Axboe
2014-09-19 18:11                         ` Christoph Hellwig
     [not found]                     ` <541C4DF1.4090604-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>
2014-10-01 16:08                       ` Bart Van Assche
2014-10-01 16:54                         ` Jens Axboe
2014-10-01 21:14                           ` Christoph Hellwig
     [not found]                           ` <542C31C4.1020702-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>
2014-10-02 16:45                             ` Bart Van Assche
2014-10-02 16:55                               ` Jens Axboe
     [not found]                                 ` <542D8368.8080604-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>
2014-10-03 13:01                                   ` Bart Van Assche
2014-10-03 14:24                                     ` Jens Axboe
     [not found]                               ` <542D8143.3050305-HInyCGIudOg@public.gmane.org>
2014-10-02 17:30                                 ` Christoph Hellwig
2014-10-06 11:16                                   ` Bart Van Assche
     [not found]                                     ` <54327A21.6070202-HInyCGIudOg@public.gmane.org>
2014-10-10 20:16                                       ` Roland Dreier
2014-09-23 16:32     ` Sagi Grimberg
     [not found]       ` <5421A093.1070203-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>
2014-09-23 19:02         ` Bart Van Assche
2014-09-24 12:22           ` Sagi Grimberg [this message]
2014-09-24 13:13             ` Bart Van Assche
     [not found]               ` <5422C395.7090902-HInyCGIudOg@public.gmane.org>
2014-09-24 13:38                 ` Sagi Grimberg
     [not found]                   ` <5422C970.4050306-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>
2014-09-24 13:43                     ` Sagi Grimberg
2014-10-07 12:51         ` Bart Van Assche
     [not found]           ` <5433E1B5.1030103-HInyCGIudOg@public.gmane.org>
2014-10-13  8:17             ` Sagi Grimberg
     [not found]               ` <543B8AB0.1090704-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>
2014-10-13  8:52                 ` Bart Van Assche
2014-10-01 16:14   ` [PATCH RFC] scsi_tcq.h: Add support for multiple hardware queues Bart Van Assche
2014-09-19 12:59 ` [PATCH 6/8] IB/srp: Avoid that I/O hangs due to a cable pull during LUN scanning Bart Van Assche
2014-09-19 12:59 ` [PATCH 7/8] IB/srp: Separate target and channel variables Bart Van Assche
2014-09-19 18:47   ` Sagi Grimberg
     [not found]   ` <541C28C8.7000007-HInyCGIudOg@public.gmane.org>
2014-09-23 16:07     ` Sagi Grimberg
2014-09-23 20:00       ` Bart Van Assche
2014-09-19 18:31 ` [PATCH RFC 0/8] IB/srp: Add multichannel support Jens Axboe
2014-09-22 14:37 ` Christoph Hellwig
     [not found]   ` <20140922143731.GA15377-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2014-09-22 16:25     ` Bart Van Assche
2014-09-22 16:31       ` Jens Axboe
2014-09-22 16:39         ` Jens Axboe

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