All of lore.kernel.org
 help / color / mirror / Atom feed
From: Grant Grundler <iod00d@hp.com>
To: linux-ia64@vger.kernel.org
Subject: Re: SCSI ERRORS triggered by BIO_VMERGE_BOUNDARY
Date: Tue, 24 Jun 2003 21:07:17 +0000	[thread overview]
Message-ID: <marc-linux-ia64-105648893606349@msgid-missing> (raw)
In-Reply-To: <marc-linux-ia64-105604433402604@msgid-missing>

On Mon, Jun 23, 2003 at 03:05:49PM -0700, Grant Grundler wrote:
> It looks like blk_recount_segments() is only used to gather
> stastics about how many segments are in the transaction.
> I tracked back to fs/bio.c to find the consumer of this
> information (# of segments) but didn't find it.
> Anyone know off hand?

James Bottomley explained it to me:

| The second is this nr_phys_segments in the elevator queuing code.  This   
| counts the number of SG entries that will be required to describe the
| request.  A lot of devices have fixed size SG tables, so the SG table is
| the only thing that limits the size of the transfer.  Thus the block
| layer has code that tries to merge physically contiguous segments of a
| bio so it can squeeze extra blocks into the transfer.

I don't know if LSI SCSI controllers/drivers have limits in this space
and what they might be. Will try to figure that out.

thanks,
grant

      parent reply	other threads:[~2003-06-24 21:07 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-06-19 17:36 SCSI ERRORS triggered by BIO_VMERGE_BOUNDARY David Mosberger
2003-06-19 20:48 ` Jesse Barnes
2003-06-19 21:47 ` Grant Grundler
2003-06-23  7:11 ` Grant Grundler
2003-06-23 15:04 ` Alex Williamson
2003-06-23 16:52 ` David Mosberger
2003-06-23 20:24 ` Grant Grundler
2003-06-23 20:41 ` David Mosberger
2003-06-23 22:05 ` Grant Grundler
2003-06-23 22:14 ` David Mosberger
2003-06-24 21:07 ` Grant Grundler [this message]

Reply instructions:

You may reply publicly 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=marc-linux-ia64-105648893606349@msgid-missing \
    --to=iod00d@hp.com \
    --cc=linux-ia64@vger.kernel.org \
    /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
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.