From: Douglas Gilbert <dougg@torque.net>
To: Andrew Morton <akpm@zip.com.au>, linux-kernel@vger.kernel.org
Subject: Re: Bio pool & scsi scatter gather pool usage
Date: Thu, 18 Apr 2002 19:11:43 -0400 [thread overview]
Message-ID: <3CBF52AF.38B7DC49@torque.net> (raw)
Andrew Morton <akpm@zip.com.au> wrote:
<snip/>
> Right now, BIO_MAX_SECTORS is only 64k, and IDE can
> take twice that. I'm not sure what the largest
> request size is for SCSI - certainly 128k.
Scatter gather lists in the scsi subsystem have a max
length of 255. The actual maximum size is dictated by
the HBA driver (sg_tablesize). The HBA driver can
further throttle the size of a single transfer with
max_sectors.
Experiments with raw IO (both in 2.4 and 2.5) indicate
that pages are not contiguous when the scatter gather
list is built. On i386 this limits the maximum transfer
size of a single scsi command to just less than 1 MB.
Doug Gilbert
next reply other threads:[~2002-04-18 23:16 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-04-18 23:11 Douglas Gilbert [this message]
-- strict thread matches above, loose matches on Subject: below --
2002-04-18 22:58 Bio pool & scsi scatter gather pool usage Mark Peloquin
2002-04-18 23:36 ` Alan Cox
2002-04-18 23:48 ` Andrew Morton
2002-04-19 7:29 ` Stephen Lord
2002-04-19 8:08 ` Joe Thornber
2002-04-19 8:51 ` Alan Cox
2002-04-19 8:58 ` Alan Cox
2002-04-19 15:27 ` Steve Lord
2002-04-19 15:57 ` Alan Cox
2002-04-19 15:51 ` Rik van Riel
2002-04-22 6:50 ` Suparna Bhattacharya
2002-04-22 7:06 ` arjan
2002-04-22 7:54 ` Suparna Bhattacharya
2002-04-24 10:20 ` Helge Hafting
2002-04-19 18:15 ` Oliver Xymoron
2002-04-18 18:23 Mark Peloquin
2002-04-18 18:57 ` Andrew Morton
2002-04-19 15:44 ` Denis Vlasenko
2002-04-25 19:43 ` Mike Fedyk
2002-04-25 19:56 ` Andrew Morton
2002-04-25 19:59 ` David Mansfield
2002-04-18 13:58 Mark Peloquin
2002-04-18 16:17 ` Andrew Morton
2002-04-18 17:35 ` Andrew Morton
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