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From: Danil Kipnis <danil.kipnis@cloud.ionos.com>
To: Bart Van Assche <bvanassche@acm.org>
Cc: Jack Wang <jinpuwang@gmail.com>,
	linux-block@vger.kernel.org, linux-rdma@vger.kernel.org,
	Jens Axboe <axboe@kernel.dk>,
	Christoph Hellwig <hch@infradead.org>,
	Sagi Grimberg <sagi@grimberg.me>,
	Jason Gunthorpe <jgg@mellanox.com>,
	Doug Ledford <dledford@redhat.com>,
	rpenyaev@suse.de, Jack Wang <jinpu.wang@cloud.ionos.com>,
	Roman Pen <r.peniaev@gmail.com>
Subject: Re: [PATCH v4 17/25] ibnbd: client: main functionality
Date: Wed, 18 Sep 2019 09:14:18 +0200
Message-ID: <CAHg0HuzQOH4ZCe+v-GHu8jOYm-wUbh1fFRK75Muq+DPpQGAH8A@mail.gmail.com> (raw)
In-Reply-To: <CAHg0HuwFTVsCNHbiXW20P6hQ3c-P_p5tB6dYKtOW=_euWEvLnA@mail.gmail.com>

> > > On Sat, Sep 14, 2019 at 1:46 AM Bart Van Assche <bvanassche@acm.org> wrote:
> > >> A more general question is why ibnbd needs its own queue management
> > >> while no other block driver needs this?
> > >
> > > Each IBNBD device promises to have a queue_depth (of say 512) on each
> > > of its num_cpus hardware queues. In fact we can only process a
> > > queue_depth inflights at once on the whole ibtrs session connecting a
> > > given client with a given server. Those 512 inflights (corresponding
> > > to the number of buffers reserved by the server for this particular
> > > client) have to be shared among all the devices mapped on this
> > > session. This leads to the situation, that we receive more requests
> > > than we can process at the moment. So we need to stop queues and start
> > > them again later in some fair fashion.
> >
> > Can a single CPU really sustain a queue depth of 512 commands? Is it
> > really necessary to have one hardware queue per CPU or is e.g. four
> > queues per NUMA node sufficient? Has it been considered to send the
> > number of hardware queues that the initiator wants to use and also the
> > command depth per queue during login to the target side? That would
> > allow the target side to allocate an independent set of buffers for each
> > initiator hardware queue and would allow to remove the queue management
> > at the initiator side. This might even yield better performance.
> We needed a way which would allow us to address one particular
> requirement: we'd like to be able to "enforce" that a response to an
> IO would be processed on the same CPU the IO was originally submitted
> on. In order to be able to do so we establish one rdma connection per
> cpu, each having a separate cq_vector. The administrator can then
> assign the corresponding IRQs to distinct CPUs. The server always
> replies to an IO on the same connection he received the request on. If
> the administrator did configure the /proc/irq/y/smp_affinity
> accordingly, the response sent by the server will generate interrupt
> on the same cpu, the IO was originally submitted on. The administrator
> can configure IRQs differently, for example assign a given irq
> (<->cq_vector) to a range of cpus belonging to a numa node, or
> whatever assignment is best for his use-case.
> Our transport module IBTRS establishes number of cpus connections
> between a client and a server. The user of the transport module (i.e.
> IBNBD) has no knowledge about the rdma connections, it only has a
> pointer to an abstract "session", which connects  him somehow to a
> remote host. IBNBD as a user of IBTRS creates block devices and uses a
> given "session" to send IOs from all the block devices it created for
> that session. That means IBNBD is limited in maximum number of his
> inflights toward a given remote host by the capability of the
> corresponding "session". So it needs to share the resources provided
> by the session (in our current model those resources are in fact some
> pre registered buffers on server side) among his devices.
> It is possible to extend the IBTRS API so that the user (IBNBD) could
> specify how many connections he wants to have on the session to be
> established. It is also possible to extend the ibtrs_clt_get_tag API
> (this is to get a send "permit") with a parameter specifying the
> connection, the future IO is to be send on.
> We now might have to change our communication model in IBTRS a bit in
> order to fix the potential security problem raised during the recent
> RDMA MC: https://etherpad.net/p/LPC2019_RDMA.
>
I'm not familiar with dm code, but don't they need to deal with the
same situation: if I configure 100 logical volumes on top of a single
NVME drive with X hardware queues, each queue_depth deep, then each dm
block device would need to advertise X hardware queues in order to
achieve highest performance in case only this one volume is accessed,
while in fact those X physical queues have to be shared among all 100
logical volumes, if they are accessed in parallel?

  reply index

Thread overview: 123+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20190620150337.7847-1-jinpuwang@gmail.com>
2019-06-20 15:03 ` [PATCH v4 01/25] sysfs: export sysfs_remove_file_self() Jack Wang
2019-09-23 17:21   ` Bart Van Assche
2019-09-25  9:30     ` Danil Kipnis
2019-07-09  9:55 ` [PATCH v4 00/25] InfiniBand Transport (IBTRS) and Network Block Device (IBNBD) Danil Kipnis
2019-07-09 11:00   ` Leon Romanovsky
2019-07-09 11:17     ` Greg KH
2019-07-09 11:57       ` Jinpu Wang
2019-07-09 13:32       ` Leon Romanovsky
2019-07-09 15:39       ` Bart Van Assche
2019-07-09 11:37     ` Jinpu Wang
2019-07-09 12:06       ` Jason Gunthorpe
2019-07-09 13:15         ` Jinpu Wang
2019-07-09 13:19           ` Jason Gunthorpe
2019-07-09 14:17             ` Jinpu Wang
2019-07-09 21:27             ` Sagi Grimberg
2019-07-19 13:12               ` Danil Kipnis
2019-07-10 14:55     ` Danil Kipnis
2019-07-09 12:04   ` Jason Gunthorpe
2019-07-09 19:45   ` Sagi Grimberg
2019-07-10 13:55     ` Jason Gunthorpe
2019-07-10 16:25       ` Sagi Grimberg
2019-07-10 17:25         ` Jason Gunthorpe
2019-07-10 19:11           ` Sagi Grimberg
2019-07-11  7:27             ` Danil Kipnis
2019-07-11  8:54     ` Danil Kipnis
2019-07-12  0:22       ` Sagi Grimberg
2019-07-12  7:57         ` Jinpu Wang
2019-07-12 19:40           ` Sagi Grimberg
2019-07-15 11:21             ` Jinpu Wang
2019-07-12 10:58         ` Danil Kipnis
     [not found] ` <20190620150337.7847-26-jinpuwang@gmail.com>
2019-07-09 15:10   ` [PATCH v4 25/25] MAINTAINERS: Add maintainer for IBNBD/IBTRS modules Leon Romanovsky
2019-07-09 15:18     ` Jinpu Wang
2019-07-09 15:51       ` Leon Romanovsky
2019-09-13 23:56   ` Bart Van Assche
2019-09-19 10:30     ` Jinpu Wang
     [not found] ` <20190620150337.7847-16-jinpuwang@gmail.com>
2019-09-13 22:10   ` [PATCH v4 15/25] ibnbd: private headers with IBNBD protocol structs and helpers Bart Van Assche
2019-09-15 14:30     ` Jinpu Wang
2019-09-16  5:27       ` Leon Romanovsky
2019-09-16 13:45         ` Bart Van Assche
2019-09-17 15:41           ` Leon Romanovsky
2019-09-17 15:52             ` Jinpu Wang
2019-09-16  7:08       ` Danil Kipnis
2019-09-16 14:57       ` Jinpu Wang
2019-09-16 17:25         ` Bart Van Assche
2019-09-17 12:27           ` Jinpu Wang
2019-09-16 15:39       ` Jinpu Wang
2019-09-18 15:26         ` Bart Van Assche
2019-09-18 16:11           ` Jinpu Wang
     [not found] ` <20190620150337.7847-17-jinpuwang@gmail.com>
2019-09-13 22:25   ` [PATCH v4 16/25] ibnbd: client: private header with client structs and functions Bart Van Assche
2019-09-17 16:36     ` Jinpu Wang
2019-09-25 23:43       ` Danil Kipnis
2019-09-26 10:00         ` Jinpu Wang
     [not found] ` <20190620150337.7847-18-jinpuwang@gmail.com>
2019-09-13 23:46   ` [PATCH v4 17/25] ibnbd: client: main functionality Bart Van Assche
2019-09-16 14:17     ` Danil Kipnis
2019-09-16 16:46       ` Bart Van Assche
2019-09-17 11:39         ` Danil Kipnis
2019-09-18  7:14           ` Danil Kipnis [this message]
2019-09-18 15:47             ` Bart Van Assche
2019-09-20  8:29               ` Danil Kipnis
2019-09-25 22:26               ` Danil Kipnis
2019-09-26  9:55                 ` Roman Penyaev
2019-09-26 15:01                   ` Bart Van Assche
2019-09-27  8:52                     ` Roman Penyaev
2019-09-27  9:32                       ` Danil Kipnis
2019-09-27 12:18                         ` Danil Kipnis
2019-09-27 16:37                       ` Bart Van Assche
2019-09-27 16:50                         ` Roman Penyaev
2019-09-27 17:16                           ` Bart Van Assche
2019-09-17 13:09     ` Jinpu Wang
2019-09-17 16:46       ` Bart Van Assche
2019-09-18 12:02         ` Jinpu Wang
2019-09-18 16:05     ` Jinpu Wang
2019-09-14  0:00   ` Bart Van Assche
     [not found] ` <20190620150337.7847-25-jinpuwang@gmail.com>
2019-09-13 23:58   ` [PATCH v4 24/25] ibnbd: a bit of documentation Bart Van Assche
2019-09-18 12:22     ` Jinpu Wang
     [not found] ` <20190620150337.7847-19-jinpuwang@gmail.com>
2019-09-18 16:28   ` [PATCH v4 18/25] ibnbd: client: sysfs interface functions Bart Van Assche
2019-09-19 15:55     ` Jinpu Wang
     [not found] ` <20190620150337.7847-21-jinpuwang@gmail.com>
2019-09-18 17:41   ` [PATCH v4 20/25] ibnbd: server: main functionality Bart Van Assche
2019-09-20  7:36     ` Danil Kipnis
2019-09-20 15:42       ` Bart Van Assche
2019-09-23 15:19         ` Danil Kipnis
     [not found] ` <20190620150337.7847-22-jinpuwang@gmail.com>
2019-09-18 21:46   ` [PATCH v4 21/25] ibnbd: server: functionality for IO submission to file or block dev Bart Van Assche
2019-09-26 14:04     ` Jinpu Wang
2019-09-26 15:11       ` Bart Van Assche
2019-09-26 15:25         ` Danil Kipnis
2019-09-26 15:29           ` Bart Van Assche
2019-09-26 15:38             ` Danil Kipnis
2019-09-26 15:42               ` Jinpu Wang
     [not found] ` <20190620150337.7847-3-jinpuwang@gmail.com>
2019-09-23 17:44   ` [PATCH v4 02/25] ibtrs: public interface header to establish RDMA connections Bart Van Assche
2019-09-25 10:20     ` Danil Kipnis
2019-09-25 15:38       ` Bart Van Assche
     [not found] ` <20190620150337.7847-7-jinpuwang@gmail.com>
2019-09-23 21:51   ` [PATCH v4 06/25] ibtrs: client: main functionality Bart Van Assche
2019-09-25 17:36     ` Danil Kipnis
2019-09-25 18:55       ` Bart Van Assche
2019-09-25 20:50         ` Danil Kipnis
2019-09-25 21:08           ` Bart Van Assche
2019-09-25 21:16             ` Bart Van Assche
2019-09-25 22:53             ` Danil Kipnis
2019-09-25 23:21               ` Bart Van Assche
2019-09-26  9:16                 ` Danil Kipnis
     [not found] ` <20190620150337.7847-4-jinpuwang@gmail.com>
2019-09-23 22:50   ` [PATCH v4 03/25] ibtrs: private headers with IBTRS protocol structs and helpers Bart Van Assche
2019-09-25 21:45     ` Danil Kipnis
2019-09-25 21:57       ` Bart Van Assche
2019-09-27  8:56     ` Jinpu Wang
     [not found] ` <20190620150337.7847-5-jinpuwang@gmail.com>
2019-09-23 23:03   ` [PATCH v4 04/25] ibtrs: core: lib functions shared between client and server modules Bart Van Assche
2019-09-27 10:13     ` Jinpu Wang
     [not found] ` <20190620150337.7847-6-jinpuwang@gmail.com>
2019-09-23 23:05   ` [PATCH v4 05/25] ibtrs: client: private header with client structs and functions Bart Van Assche
2019-09-27 10:18     ` Jinpu Wang
     [not found] ` <20190620150337.7847-8-jinpuwang@gmail.com>
2019-09-23 23:15   ` [PATCH v4 07/25] ibtrs: client: statistics functions Bart Van Assche
2019-09-27 12:00     ` Jinpu Wang
     [not found] ` <20190620150337.7847-10-jinpuwang@gmail.com>
2019-09-23 23:21   ` [PATCH v4 09/25] ibtrs: server: private header with server structs and functions Bart Van Assche
2019-09-27 12:04     ` Jinpu Wang
     [not found] ` <20190620150337.7847-11-jinpuwang@gmail.com>
2019-09-23 23:49   ` [PATCH v4 10/25] ibtrs: server: main functionality Bart Van Assche
2019-09-27 15:03     ` Jinpu Wang
2019-09-27 15:11       ` Bart Van Assche
2019-09-27 15:19         ` Jinpu Wang
     [not found] ` <20190620150337.7847-12-jinpuwang@gmail.com>
2019-09-23 23:56   ` [PATCH v4 11/25] ibtrs: server: statistics functions Bart Van Assche
2019-10-02 15:15     ` Jinpu Wang
2019-10-02 15:42       ` Leon Romanovsky
2019-10-02 15:45         ` Jinpu Wang
2019-10-02 16:00           ` Leon Romanovsky
     [not found] ` <20190620150337.7847-13-jinpuwang@gmail.com>
2019-09-24  0:00   ` [PATCH v4 12/25] ibtrs: server: sysfs interface functions Bart Van Assche
2019-10-02 15:11     ` Jinpu Wang

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