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From: Mike Christie <>
To: Jens Axboe <>,
Subject: [PATCH] update max_sectors documentation
Date: Tue, 07 Mar 2006 18:27:01 -0600	[thread overview]
Message-ID: <1141777621.5594.3.camel@max> (raw)

Hi Jens,

I was looking over Kai's scsi command size email and was going to try
and add it to some block docs and noticed I did not send the update to
the max_sectors biodoc.txt. Sorry about that. Here is the patch against

The max_sectors has been split into max_hw_sectors and max_sectors for some
time. A patch to have blk_queue_max_sectors enforce this was sent by
me and it broke IDE. This patch updates the documentation.

--- linux-2.6.16-rc5/Documentation/block/biodoc.txt	2006-02-26 23:09:35.000000000 -0600
+++	2006-03-07 18:10:57.000000000 -0600
@@ -132,8 +132,18 @@ Some new queue property settings:
 		limit. No highmem default.
 	blk_queue_max_sectors(q, max_sectors)
-		Maximum size request you can handle in units of 512 byte
-		sectors. 255 default.
+		Sets two variables that limit the size of the request.
+		- The request queue's max_sectors, which is a soft size in
+		in units of 512 byte sectors, and could be dynamically varied
+		by the core kernel.
+		- The request queue's max_hw_sectors, which is a hard limit
+		and reflects the maximum size request a driver can handle
+		in units of 512 byte sectors.
+		The default for both max_sectors and max_hw_sectors is
+		255. The upper limit of max_sectors is 1024.
 	blk_queue_max_phys_segments(q, max_segments)
 		Maximum physical segments you can handle in a request. 128

             reply	other threads:[~2006-03-08  0:27 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-03-08  0:27 Mike Christie [this message]
2006-03-08 10:17 ` Jens Axboe

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