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From: Sagi Grimberg <sagi@grimberg.me>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Danil Kipnis <danil.kipnis@cloud.ionos.com>,
	Jack Wang <jinpuwang@gmail.com>,
	linux-block@vger.kernel.org, linux-rdma@vger.kernel.org,
	axboe@kernel.dk, Christoph Hellwig <hch@infradead.org>,
	bvanassche@acm.org, dledford@redhat.com,
	Roman Pen <r.peniaev@gmail.com>,
	gregkh@linuxfoundation.org
Subject: Re: [PATCH v4 00/25] InfiniBand Transport (IBTRS) and Network Block Device (IBNBD)
Date: Wed, 10 Jul 2019 09:25:05 -0700	[thread overview]
Message-ID: <c49bf227-5274-9d13-deba-a405c75d1358@grimberg.me> (raw)
In-Reply-To: <20190710135519.GA4051@ziepe.ca>


>> Another question, from what I understand from the code, the client
>> always rdma_writes data on writes (with imm) from a remote pool of
>> server buffers dedicated to it. Essentially all writes are immediate (no
>> rdma reads ever). How is that different than using send wrs to a set of
>> pre-posted recv buffers (like all others are doing)? Is it faster?
> 
> RDMA WRITE only is generally a bit faster, and if you use a buffer
> pool in a smart way it is possible to get very good data packing.

There is no packing, its used exactly as send/recv, but with a remote
buffer pool (pool of 512K buffers) and the client selects one and rdma
write with imm to it.

> With
> SEND the number of recvq entries dictates how big the rx buffer can
> be, or you waste even more memory by using partial send buffers..

This is exactly how it used here.

> A scheme like this seems like a high performance idea, but on the
> other side, I have no idea how you could possibly manage invalidations
> efficiently with a shared RX buffer pool...

There are no invalidations, this remote server pool is registered once
and long lived with the session.

> The RXer has to push out an invalidation for the shared buffer pool
> MR, but we don't have protocols for partial MR invalidation.
> 
> Which is back to my earlier thought that the main reason this perfoms
> better is because it doesn't have synchronous MR invalidation.

This issue only exists on the client side. The server never
invalidates any of its buffers.

> Maybe this is fine, but it needs to be made very clear that it uses
> this insecure operating model to get higher performance..

I still do not understand why this should give any notice-able
performance advantage.

  reply	other threads:[~2019-07-10 16:25 UTC|newest]

Thread overview: 148+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-20 15:03 [PATCH v4 00/25] InfiniBand Transport (IBTRS) and Network Block Device (IBNBD) Jack Wang
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
2019-06-20 15:03 ` [PATCH v4 02/25] ibtrs: public interface header to establish RDMA connections Jack Wang
2019-09-23 17:44   ` Bart Van Assche
2019-09-25 10:20     ` Danil Kipnis
2019-09-25 15:38       ` Bart Van Assche
2019-06-20 15:03 ` [PATCH v4 03/25] ibtrs: private headers with IBTRS protocol structs and helpers Jack Wang
2019-09-23 22:50   ` 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
2019-06-20 15:03 ` [PATCH v4 04/25] ibtrs: core: lib functions shared between client and server modules Jack Wang
2019-09-23 23:03   ` Bart Van Assche
2019-09-27 10:13     ` Jinpu Wang
2019-06-20 15:03 ` [PATCH v4 05/25] ibtrs: client: private header with client structs and functions Jack Wang
2019-09-23 23:05   ` Bart Van Assche
2019-09-27 10:18     ` Jinpu Wang
2019-06-20 15:03 ` [PATCH v4 06/25] ibtrs: client: main functionality Jack Wang
2019-09-23 21:51   ` 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
2019-06-20 15:03 ` [PATCH v4 07/25] ibtrs: client: statistics functions Jack Wang
2019-09-23 23:15   ` Bart Van Assche
2019-09-27 12:00     ` Jinpu Wang
2019-06-20 15:03 ` [PATCH v4 08/25] ibtrs: client: sysfs interface functions Jack Wang
2019-06-20 15:03 ` [PATCH v4 09/25] ibtrs: server: private header with server structs and functions Jack Wang
2019-09-23 23:21   ` Bart Van Assche
2019-09-27 12:04     ` Jinpu Wang
2019-06-20 15:03 ` [PATCH v4 10/25] ibtrs: server: main functionality Jack Wang
2019-09-23 23:49   ` 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
2019-06-20 15:03 ` [PATCH v4 11/25] ibtrs: server: statistics functions Jack Wang
2019-09-23 23:56   ` 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
2019-06-20 15:03 ` [PATCH v4 12/25] ibtrs: server: sysfs interface functions Jack Wang
2019-09-24  0:00   ` Bart Van Assche
2019-10-02 15:11     ` Jinpu Wang
2019-06-20 15:03 ` [PATCH v4 13/25] ibtrs: include client and server modules into kernel compilation Jack Wang
2019-06-20 15:03 ` [PATCH v4 14/25] ibtrs: a bit of documentation Jack Wang
2019-06-20 15:03 ` [PATCH v4 15/25] ibnbd: private headers with IBNBD protocol structs and helpers Jack Wang
2019-09-13 22:10   ` 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
2019-06-20 15:03 ` [PATCH v4 16/25] ibnbd: client: private header with client structs and functions Jack Wang
2019-09-13 22:25   ` Bart Van Assche
2019-09-17 16:36     ` Jinpu Wang
2019-09-25 23:43       ` Danil Kipnis
2019-09-26 10:00         ` Jinpu Wang
2019-06-20 15:03 ` [PATCH v4 17/25] ibnbd: client: main functionality Jack Wang
2019-09-13 23:46   ` 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
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
2019-06-20 15:03 ` [PATCH v4 18/25] ibnbd: client: sysfs interface functions Jack Wang
2019-09-18 16:28   ` Bart Van Assche
2019-09-19 15:55     ` Jinpu Wang
2019-06-20 15:03 ` [PATCH v4 19/25] ibnbd: server: private header with server structs and functions Jack Wang
2019-06-20 15:03 ` [PATCH v4 20/25] ibnbd: server: main functionality Jack Wang
2019-09-18 17:41   ` 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
2019-06-20 15:03 ` [PATCH v4 21/25] ibnbd: server: functionality for IO submission to file or block dev Jack Wang
2019-09-18 21:46   ` 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
2019-06-20 15:03 ` [PATCH v4 22/25] ibnbd: server: sysfs interface functions Jack Wang
2019-06-20 15:03 ` [PATCH v4 23/25] ibnbd: include client and server modules into kernel compilation Jack Wang
2019-06-20 15:03 ` [PATCH v4 24/25] ibnbd: a bit of documentation Jack Wang
2019-09-13 23:58   ` Bart Van Assche
2019-09-18 12:22     ` Jinpu Wang
2019-06-20 15:03 ` [PATCH v4 25/25] MAINTAINERS: Add maintainer for IBNBD/IBTRS modules Jack Wang
2019-07-09 15:10   ` 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
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 [this message]
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

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