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From: Erez Zilber <erezz@Voltaire.COM>
To: Bart Van Assche <bart.vanassche@gmail.com>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>,
	rdreier@cisco.com, James.Bottomley@hansenpartnership.com,
	torvalds@linux-foundation.org, akpm@linux-foundation.org,
	vst@vlnb.net, linux-scsi@vger.kernel.org,
	scst-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org
Subject: Re: Integration of SCST in the mainstream Linux kernel
Date: Mon, 18 Feb 2008 11:43:31 +0200	[thread overview]
Message-ID: <47B95343.9060802@Voltaire.COM> (raw)
In-Reply-To: <e2e108260802060416w492db372mc09848edd365d441@mail.gmail.com>

Bart Van Assche wrote:
> On Feb 5, 2008 6:01 PM, Erez Zilber <erezz@voltaire.com> wrote:
>   
>> Using such large values for FirstBurstLength will give you poor
>> performance numbers for WRITE commands (with iSER). FirstBurstLength
>> means how much data should you send as unsolicited data (i.e. without
>> RDMA). It means that your WRITE commands were sent without RDMA.
>>     
>
> Sorry, but I'm afraid you got this wrong. When the iSER transport is
> used instead of TCP, all data is sent via RDMA, including unsolicited
> data. If you have look at the iSER implementation in the Linux kernel
> (source files under drivers/infiniband/ulp/iser), you will see that
> all data is transferred via RDMA and not via TCP/IP.
>
>   

When you execute WRITE commands with iSCSI, it works like this:

EDTL (Expected data length) - the data length of your command

FirstBurstLength - the length of data that will be sent as unsolicited
data (i.e. as immediate data with the SCSI command and as unsolicited
data-out PDUs)

If you use a high value for FirstBurstLength, all (or most) of your data
will be sent as unsolicited data-out PDUs. These PDUs don't use the RDMA
engine, so you miss the advantage of IB.

If you use a lower value for FirstBurstLength, EDTL - FirstBurstLength
bytes will be sent as solicited data-out PDUs. With iSER, solicited
data-out PDUs are RDMA operations.

I hope that I'm more clear now.

Erez

  parent reply	other threads:[~2008-02-18  9:43 UTC|newest]

Thread overview: 147+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-23 14:22 Bart Van Assche
2008-01-23 17:11 ` Vladislav Bolkhovitin
2008-01-29 20:42 ` James Bottomley
2008-01-29 21:31   ` Roland Dreier
2008-01-29 23:32     ` FUJITA Tomonori
2008-01-30  1:15       ` [Scst-devel] " Vu Pham
2008-01-30  8:38       ` Bart Van Assche
2008-01-30 10:56         ` FUJITA Tomonori
2008-01-30 11:40           ` Vladislav Bolkhovitin
2008-01-30 13:10           ` Bart Van Assche
2008-01-30 13:54             ` FUJITA Tomonori
2008-01-31  7:48               ` Bart Van Assche
2008-01-31 13:25           ` Nicholas A. Bellinger
2008-01-31 14:34             ` Bart Van Assche
2008-01-31 14:44               ` Nicholas A. Bellinger
2008-01-31 15:50               ` Vladislav Bolkhovitin
2008-01-31 16:25                 ` [Scst-devel] " Joe Landman
2008-01-31 17:08                   ` Bart Van Assche
2008-01-31 17:13                     ` Joe Landman
2008-01-31 18:12                     ` David Dillow
2008-02-01 11:50                       ` Vladislav Bolkhovitin
2008-02-01 11:50                     ` Vladislav Bolkhovitin
2008-02-01 12:25                       ` Vladislav Bolkhovitin
2008-01-31 17:14                 ` Nicholas A. Bellinger
2008-01-31 17:40                   ` Bart Van Assche
2008-01-31 18:15                     ` Nicholas A. Bellinger
2008-02-01  9:08                       ` Bart Van Assche
2008-02-01  8:11             ` Bart Van Assche
2008-02-01 10:39               ` Nicholas A. Bellinger
2008-02-01 11:04                 ` Bart Van Assche
2008-02-01 12:05                   ` Nicholas A. Bellinger
2008-02-01 13:25                     ` Bart Van Assche
2008-02-01 14:36                       ` Nicholas A. Bellinger
2008-01-30 16:34         ` James Bottomley
2008-01-30 16:50           ` Bart Van Assche
2008-02-02 15:32           ` Pete Wyckoff
2008-02-05 17:01         ` Erez Zilber
2008-02-06 12:16           ` Bart Van Assche
2008-02-06 16:45             ` Benny Halevy
2008-02-06 17:06             ` Roland Dreier
2008-02-18  9:43             ` Erez Zilber [this message]
2008-02-18 11:01               ` Bart Van Assche
2008-02-20  7:34                 ` Erez Zilber
2008-02-20  8:41                   ` Bart Van Assche
2008-01-30 11:18       ` Vladislav Bolkhovitin
2008-01-30  8:29   ` Bart Van Assche
2008-01-30 16:22     ` James Bottomley
2008-01-30 17:03       ` Bart Van Assche
2008-02-05  7:14       ` [Scst-devel] " Tomasz Chmielewski
2008-02-05 13:38         ` FUJITA Tomonori
2008-02-05 16:07           ` Tomasz Chmielewski
2008-02-05 16:21             ` Ming Zhang
2008-02-05 16:43             ` FUJITA Tomonori
2008-02-05 17:09           ` Matteo Tescione
2008-02-06  1:29             ` FUJITA Tomonori
2008-02-06  2:01               ` Nicholas A. Bellinger
2008-01-30 11:17   ` Vladislav Bolkhovitin
2008-02-04 12:27     ` Vladislav Bolkhovitin
2008-02-04 13:53       ` Bart Van Assche
2008-02-04 17:00         ` David Dillow
2008-02-04 17:08         ` Vladislav Bolkhovitin
2008-02-05 16:25         ` Bart Van Assche
2008-02-05 18:18           ` Linus Torvalds
2008-02-04 15:30       ` James Bottomley
2008-02-04 16:25         ` Vladislav Bolkhovitin
2008-02-04 17:06           ` James Bottomley
2008-02-04 17:16             ` Vladislav Bolkhovitin
2008-02-04 17:25               ` James Bottomley
2008-02-04 17:56                 ` Vladislav Bolkhovitin
2008-02-04 18:22                   ` James Bottomley
2008-02-04 18:38                     ` Vladislav Bolkhovitin
2008-02-04 18:54                       ` James Bottomley
2008-02-05 18:59                         ` Vladislav Bolkhovitin
2008-02-05 19:13                           ` James Bottomley
2008-02-06 18:07                             ` Vladislav Bolkhovitin
2008-02-07 13:13                             ` [Scst-devel] " Bart Van Assche
2008-02-07 13:45                               ` Vladislav Bolkhovitin
2008-02-07 22:51                                 ` david
2008-02-08 10:37                                   ` Vladislav Bolkhovitin
2008-02-09  7:40                                     ` david
2008-02-08 11:33                                   ` Nicholas A. Bellinger
2008-02-08 14:36                                     ` Vladislav Bolkhovitin
2008-02-08 23:53                                       ` Nicholas A. Bellinger
2008-02-15 15:02                                 ` Bart Van Assche
2008-02-07 15:38                               ` [Scst-devel] " Nicholas A. Bellinger
2008-02-07 20:37                                 ` Luben Tuikov
2008-02-08 10:32                                   ` Vladislav Bolkhovitin
2008-02-09  7:32                                     ` Luben Tuikov
2008-02-11 10:02                                       ` Vladislav Bolkhovitin
2008-02-08 11:53                                   ` [Scst-devel] " Nicholas A. Bellinger
2008-02-08 14:42                                     ` Vladislav Bolkhovitin
2008-02-09  0:00                                       ` Nicholas A. Bellinger
2008-02-04 18:29                 ` Linus Torvalds
2008-02-04 18:49                   ` James Bottomley
2008-02-04 19:06                   ` Nicholas A. Bellinger
2008-02-04 19:19                     ` Nicholas A. Bellinger
2008-02-04 19:44                     ` Linus Torvalds
2008-02-04 20:06                       ` [Scst-devel] " 4news
2008-02-04 20:24                       ` Nicholas A. Bellinger
2008-02-04 21:01                       ` J. Bruce Fields
2008-02-04 21:24                         ` Linus Torvalds
2008-02-04 22:00                           ` Nicholas A. Bellinger
2008-02-04 22:57                           ` Jeff Garzik
2008-02-04 23:45                             ` Linus Torvalds
2008-02-05  0:08                               ` Jeff Garzik
2008-02-05  1:20                                 ` Linus Torvalds
2008-02-05  8:38                             ` Bart Van Assche
2008-02-05 17:50                               ` Jeff Garzik
2008-02-06 10:22                                 ` Bart Van Assche
2008-02-06 14:21                                   ` Jeff Garzik
2008-02-05 13:05                             ` Olivier Galibert
2008-02-05 18:08                               ` Jeff Garzik
2008-02-05 19:01                           ` Vladislav Bolkhovitin
2008-02-04 22:43                       ` Alan Cox
2008-02-04 17:30                         ` Douglas Gilbert
2008-02-05  2:07                           ` [Scst-devel] " Chris Weiss
2008-02-05 14:19                             ` FUJITA Tomonori
2008-02-04 22:59                         ` Nicholas A. Bellinger
2008-02-04 23:00                         ` James Bottomley
2008-02-04 23:12                           ` Nicholas A. Bellinger
2008-02-04 23:16                             ` Nicholas A. Bellinger
2008-02-05 18:37                             ` James Bottomley
2008-02-04 23:04                         ` Jeff Garzik
2008-02-04 23:27                           ` Linus Torvalds
2008-02-05 19:01                           ` Vladislav Bolkhovitin
2008-02-05 19:12                             ` Jeff Garzik
2008-02-05 19:21                               ` Vladislav Bolkhovitin
2008-02-06  0:11                                 ` Nicholas A. Bellinger
2008-02-06  1:43                                   ` Nicholas A. Bellinger
2008-02-12 16:05                                   ` [Scst-devel] " Bart Van Assche
2008-02-13  3:44                                     ` Nicholas A. Bellinger
2008-02-13  6:18                                       ` CONFIG_SLUB and reproducable general protection faults on 2.6.2x Nicholas A. Bellinger
2008-02-13 16:37                                         ` Nicholas A. Bellinger
2008-02-06  0:17                               ` Integration of SCST in the mainstream Linux kernel Nicholas A. Bellinger
2008-02-06  0:48                             ` Nicholas A. Bellinger
2008-02-06  0:51                               ` Nicholas A. Bellinger
2008-02-05  0:07                         ` Matt Mackall
2008-02-05  0:24                           ` Linus Torvalds
2008-02-05  0:42                             ` Jeff Garzik
2008-02-05  0:45                             ` Matt Mackall
2008-02-05  4:43                             ` [Scst-devel] " Matteo Tescione
2008-02-05  5:07                               ` James Bottomley
2008-02-05 13:38                               ` FUJITA Tomonori
2008-02-05 19:00                       ` Vladislav Bolkhovitin
2008-02-05 17:10 ` Erez Zilber
2008-02-05 19:02   ` Bart Van Assche
2008-02-05 19:02   ` Vladislav Bolkhovitin

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