[1498] in linux-scsi channel archive
Re: elevator sorting for the scsi subsystem.
daemon@ATHENA.MIT.EDU (Leonard N. Zubkoff)
Sun Mar 2 20:16:14 1997
Date: Sun, 2 Mar 1997 17:11:20 -0800
From: "Leonard N. Zubkoff" <lnz@dandelion.com>
To: groudier@club-internet.fr
CC: Dario_Ballabio@milano.europe.dg.com, linux-scsi@vger.rutgers.edu
In-reply-to: <Pine.LNX.3.91.970302235017.289A-100000@localhost> (message from
Gerard Roudier on Mon, 3 Mar 1997 01:03:24 +0000 (GMT))
Date: Mon, 3 Mar 1997 01:03:24 +0000 (GMT)
From: Gerard Roudier <groudier@club-internet.fr>
Well. In my opinion, the right layer for such stuff in Linux
is ll_rw_blk.
As far as I remember, disk IOs are done
this way under Linux.
1 - Plug the device.
2 - Queue IO in severall chunks. Io chunks are then coalesced and
reordered on the fly by make_request() and add_request().
Actually, we should only coalesce as many requests as can be handed off to the
host adapter as a single request. The present code is very poor in the case
where the host adapter cannot accept as large a scatter/gather list as the
make_request/add_request level created. In that case, we split the request,
but the second part is not queued separately; it has to wait for the first part
of the request to complete.
Leonard
