[8170] in linux-scsi channel archive
scatter gather or not to scatter gather
daemon@ATHENA.MIT.EDU (Matthew Dharm)
Wed Feb 23 00:46:37 2000
Date: Tue, 22 Feb 2000 18:04:53 -0800 (PST)
From: Matthew Dharm <mdharm-scsi@one-eyed-alien.net>
To: The Linux SCSI list <linux-scsi@vger.rutgers.edu>
Message-ID: <Pine.LNX.4.10.10002221759010.6488-100000@ziggy.one-eyed-alien.net>
MIME-Version: 1.0
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To scatter-gather, or not to scatter-gather; that is the question.
Basically, I'm writting a virtual host driver. I can support scatter
gather, or I can opt not to. If I don't use scatter gather, there will be
an (as yet) unquantified performance gain on the USB bus that this virtual
host uses. However, what are the negatives in terms of the SCSI
layering?
From my logs, it seems that the SCSI layer is sending me long
scatter-gather chains, where each block is 1K in size, and they tend to be
all or mostly adjacent in RAM.
The question boils down to this: Why would it be bad for me to replace the
SG_ALL in the host template with SG_NONE?
Matt Dharm
--
Matthew Dharm Home: mdharm@one-eyed-alien.net
Engineer, Qualcomm, Inc. Work: mdharm@qualcomm.com
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-- CEO
User Friendly, 4/30/1998
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