Linux-USB Archive on lore.kernel.org
 help / color / Atom feed
From: Steffen Maier <maier@linux.ibm.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: linux-scsi@vger.kernel.org,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	James Bottomley <James.Bottomley@hansenpartnership.com>,
	Bart Van Assche <bvanassche@acm.org>,
	Hannes Reinecke <hare@suse.com>, Christoph Hellwig <hch@lst.de>,
	Jim Gill <jgill@vmware.com>, Cathy Avery <cavery@redhat.com>,
	"Ewan D . Milne" <emilne@redhat.com>,
	Brian King <brking@us.ibm.com>,
	James Smart <james.smart@broadcom.com>,
	"Juergen E . Fischer" <fischer@norbit.de>,
	Michael Schmitz <schmitzmic@gmail.com>,
	Finn Thain <fthain@telegraphics.com.au>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	devel@driverdev.osuosl.org, linux-usb@vger.kernel.org,
	Dan Carpenter <dan.carpenter@oracle.com>,
	Benjamin Block <bblock@linux.ibm.com>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	linux-s390@vger.kernel.org
Subject: Re: [PATCH V5 10/16] s390: zfcp_fc: use sg helper to operate scatterlist
Date: Wed, 26 Jun 2019 10:17:33 +0200
Message-ID: <1353d755-de62-d575-4c7b-d20d59d07f23@linux.ibm.com> (raw)
In-Reply-To: <20190626030751.GA26340@ming.t460p>

Hi Ming,

On 6/26/19 5:07 AM, Ming Lei wrote:
> On Tue, Jun 25, 2019 at 12:51:04PM +0200, Steffen Maier wrote:
>> I don't mind doing this change for zfcp. However, I'm having doubts
>> regarding the rationale in the commit description.

> However, I still suggest to do it because it will make us to audit SCSI chained
> sg uses much easier. And the change shouldn't have performance effect.

>> If I was not mistaken above, the following could be more descriptive parts
>> of a patch/commit description, with hopefully less confusion for anyone
>> having to look at zfcp git history a few weeks/months/years from now:
>>
>> "While not required for this SCSI MQ change regarding scatterlist
>> allocation, change all other scatterlist iterators in zfcp to the safe
>> sg_next() even if not necessary as these changed zfcp-internal scatterlists
>> are linear and unchained. This may avoid confusion about a potential need
>> for conversions in the future."

Sure, let's change the code, but could you please update the description of 
your below new patch to something like I drafted above regarding rationale?

If you would like to send a V2, I'll be happy to give a Reviewed-by.

>>>   From c9c368308fefbf034d670984fe9746a4181fe514 Mon Sep 17 00:00:00 2001
>>> From: Ming Lei <ming.lei@redhat.com>
>>> Date: Tue, 25 Jun 2019 09:15:34 +0800
>>> Subject: [PATCH] s390: scsi: use sg helper to iterate over scatterlist

>>> Unlike the legacy I/O path, scsi-mq preallocates a large array to hold
>>> the scatterlist for each request. This static allocation can consume
>>> substantial amounts of memory on modern controllers which support a
>>> large number of concurrently outstanding requests.

>>> To facilitate a switch to a smaller static allocation combined with a
>>> dynamic allocation for requests that need it, we need to make sure all
>>> SCSI drivers handle chained scatterlists correctly.

>>> Convert remaining drivers that directly dereference the scatterlist
>>> array to using the iterator functions.

> OK, I still suggest to apply the patch for the mentioned reason if you
> are fine.



-- 
Mit freundlichen Gruessen / Kind regards
Steffen Maier

Linux on IBM Z Development

https://www.ibm.com/privacy/us/en/
IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Matthias Hartmann
Geschaeftsfuehrung: Dirk Wittkopp
Sitz der Gesellschaft: Boeblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294


  reply index

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-18  1:37 [PATCH V5 00/16] " Ming Lei
2019-06-18  1:37 ` [PATCH V5 01/16] scsi: vmw_pscsi: " Ming Lei
2019-06-18  1:37 ` [PATCH V5 02/16] scsi: advansys: " Ming Lei
2019-06-18  1:37 ` [PATCH V5 03/16] scsi: lpfc: " Ming Lei
2019-06-18  1:37 ` [PATCH V5 04/16] scsi: mvumi: " Ming Lei
2019-06-18  1:37 ` [PATCH V5 05/16] scsi: ipr: " Ming Lei
2019-06-18  1:37 ` [PATCH V5 06/16] scsi: pmcraid: " Ming Lei
2019-06-18  1:37 ` [PATCH V5 07/16] usb: image: microtek: " Ming Lei
2019-06-18  1:37 ` [PATCH V5 08/16] staging: unisys: visorhba: " Ming Lei
2019-06-18  1:37 ` [PATCH V5 09/16] staging: rtsx: " Ming Lei
2019-06-18  1:37 ` [PATCH V5 10/16] s390: zfcp_fc: " Ming Lei
2019-06-24 15:13   ` Steffen Maier
2019-06-25  1:19     ` Ming Lei
2019-06-25  2:01       ` Finn Thain
2019-06-25  2:30         ` Ming Lei
2019-06-25  3:42           ` Finn Thain
2019-06-25 10:51       ` Steffen Maier
2019-06-26  3:07         ` Ming Lei
2019-06-26  8:17           ` Steffen Maier [this message]
2019-06-18  1:37 ` [PATCH V5 11/16] scsi: aha152x: " Ming Lei
2019-06-18  3:54   ` Finn Thain
2019-06-18  1:37 ` [PATCH V5 12/16] scsi: imm: " Ming Lei
2019-06-18  1:37 ` [PATCH V5 13/16] scsi: pcmcia: nsp_cs: " Ming Lei
2019-06-18  1:37 ` [PATCH V5 14/16] scsi: ppa: " Ming Lei
2019-06-18  1:37 ` [PATCH V5 15/16] scsi: wd33c93: " Ming Lei
2019-06-18  1:37 ` [PATCH V5 16/16] NCR5380: Support chained sg lists Ming Lei
2019-06-19  0:29 ` [PATCH V5 00/16] use sg helper to operate scatterlist Martin K. Petersen
2019-06-19 19:43   ` Bart Van Assche
2019-06-19 19:55     ` Martin K. Petersen
2019-06-24 12:40       ` Ming Lei
2019-06-24 12:54         ` Martin K. Petersen

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1353d755-de62-d575-4c7b-d20d59d07f23@linux.ibm.com \
    --to=maier@linux.ibm.com \
    --cc=James.Bottomley@hansenpartnership.com \
    --cc=bblock@linux.ibm.com \
    --cc=brking@us.ibm.com \
    --cc=bvanassche@acm.org \
    --cc=cavery@redhat.com \
    --cc=dan.carpenter@oracle.com \
    --cc=devel@driverdev.osuosl.org \
    --cc=emilne@redhat.com \
    --cc=fischer@norbit.de \
    --cc=fthain@telegraphics.com.au \
    --cc=gregkh@linuxfoundation.org \
    --cc=hare@suse.com \
    --cc=hch@lst.de \
    --cc=heiko.carstens@de.ibm.com \
    --cc=james.smart@broadcom.com \
    --cc=jgill@vmware.com \
    --cc=linux-s390@vger.kernel.org \
    --cc=linux-scsi@vger.kernel.org \
    --cc=linux-usb@vger.kernel.org \
    --cc=martin.petersen@oracle.com \
    --cc=ming.lei@redhat.com \
    --cc=schmitzmic@gmail.com \
    --cc=schwidefsky@de.ibm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-USB Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-usb/0 linux-usb/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-usb linux-usb/ https://lore.kernel.org/linux-usb \
		linux-usb@vger.kernel.org linux-usb@archiver.kernel.org
	public-inbox-index linux-usb


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-usb


AGPL code for this site: git clone https://public-inbox.org/ public-inbox