From: Douglas Gilbert <dougg@torque.net>
To: James Bottomley <James.Bottomley@SteelEye.com>
Cc: Jens Axboe <axboe@suse.de>,
Kai Makisara <Kai.Makisara@kolumbus.fi>,
matthew@wil.cx, linux-scsi@vger.kernel.org
Subject: Re: [PATCH] SCSI sym53c8xx_2: bigger transfer limits
Date: Wed, 01 Mar 2006 11:00:56 -0500 [thread overview]
Message-ID: <4405C538.4050709@torque.net> (raw)
In-Reply-To: <1141227541.3276.26.camel@mulgrave.il.steeleye.com>
James Bottomley wrote:
> On Wed, 2006-03-01 at 16:29 +0100, Jens Axboe wrote:
>
>>Strictly speaking, the clustering bit is unrelated. I seem to recall
>>Gerard years ago talking about some sym chips that did not like
>>clustering, hence it was disabled.
>
>
> Yes, I remember that too ... I've never been able to find out which
> chip, though ... the scripts all seem happily coded for variable size sg
> segments.
>
> However, given the new way 2.6 does memory allocations,
> ENABLE_CLUSTERING will probably make quite a difference to the size of
> the sg list ... since we try to allocate contiguous pages, physical
> merging becomes much more of a possibility (I think I last measured it
> at around 30% of all SG tables, as opposed to <1% with the old
> allocation method).
James,
So the maximum data carrying size of a scatter gather list
is not deterministic? Is the worst case (page_size * SG_ALL)?
Doug Gilbert
next prev parent reply other threads:[~2006-03-01 16:02 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-28 19:14 [PATCH] SCSI sym53c8xx_2: bigger transfer limits Kai Makisara
2006-02-28 20:41 ` Matthew Wilcox
2006-03-01 15:29 ` Jens Axboe
2006-03-01 15:39 ` James Bottomley
2006-03-01 15:54 ` Jens Axboe
2006-03-01 16:00 ` Douglas Gilbert [this message]
2006-03-01 16:11 ` Jens Axboe
2006-03-01 16:17 ` James Bottomley
2006-03-01 20:34 ` Kai Makisara
2006-03-01 20:43 ` Jens Axboe
2006-03-01 22:24 ` Kai Makisara
2006-03-02 3:57 ` Matthew Wilcox
2006-03-02 7:29 ` Jens Axboe
2006-03-04 8:16 ` Kai Makisara
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