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From: Bart Van Assche <bvanassche@acm.org>
To: Roman Penyaev <r.peniaev@gmail.com>
Cc: Danil Kipnis <danil.kipnis@cloud.ionos.com>,
	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>
Subject: Re: [PATCH v4 17/25] ibnbd: client: main functionality
Date: Fri, 27 Sep 2019 09:37:39 -0700
Message-ID: <b31be034-eae0-77f7-aabf-92c8f8a984e5@acm.org> (raw)
In-Reply-To: <CACZ9PQU8=4DaSAUQ7czKdcWio2H5HB1ro-pXaY2VP9PhgTxk7g@mail.gmail.com>

On 9/27/19 1:52 AM, Roman Penyaev wrote:
> No, it seems this thingy is a bit different.  According to my
> understanding patches 3 and 4 from this patchset do the
> following: 1# split equally the whole queue depth on number
> of hardware queues and 2# return tag number which is unique
> host-wide (more or less similar to unique_tag, right?).
> 
> 2# is not needed for ibtrs, and 1# can be easy done by dividing
> queue_depth on number of hw queues on tag set allocation, e.g.
> something like the following:
> 
>      ...
>      tags->nr_hw_queues = num_online_cpus();
>      tags->queue_depth  = sess->queue_deph / tags->nr_hw_queues;
> 
>      blk_mq_alloc_tag_set(tags);
> 
> 
> And this trick won't work out for the performance.  ibtrs client
> has a single resource: set of buffer chunks received from a
> server side.  And these buffers should be dynamically distributed
> between IO producers according to the load.  Having a hard split
> of the whole queue depth between hw queues we can forget about a
> dynamic load distribution, here is an example:
> 
>     - say server shares 1024 buffer chunks for a session (do not
>       remember what is the actual number).
> 
>     - 1024 buffers are equally divided between hw queues, let's
>       say 64 (number of cpus), so each queue is 16 requests depth.
> 
>     - only several CPUs produce IO, and instead of occupying the
>       whole "bandwidth" of a session, i.e. 1024 buffer chunks,
>       we limit ourselves to a small queue depth of an each hw
>       queue.
> 
> And performance drops significantly when number of IO producers
> is smaller than number of hw queues (CPUs), and it can be easily
> tested and proved.
> 
> So for this particular ibtrs case tags should be globally shared,
> and seems (unfortunately) there is no any other similar requirements
> for other block devices.

Hi Roman,

I agree that BLK_MQ_F_HOST_TAGS partitions a tag set across hardware 
queues while ibnbd shares a single tag set across multiple hardware 
queues. Since such sharing may be useful for other block drivers, isn't 
that something that should be implemented in the block layer core 
instead of in the ibnbd driver? If that logic would be moved into the 
block layer core, would that allow to reuse the queue restarting logic 
that already exists in the block layer core?

Thanks,

Bart.

  parent 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
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 [this message]
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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