[Fwd: Re: (2.6.0-test9) usb_storage/uhci_hcd much slower write than linux-2.4]

[Chuck Mead]

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FYI!

- -------- Original Message --------
Subject:     Re: (2.6.0-test9) usb_storage/uhci_hcd much slower write than
linux-2.4
Date:     Mon, 03 Nov 2003 17:17:25 -0500
From:     Tim Shepard <shep at alum.mit.edu>
To:     linux-usb-devel at lists.sourceforge.net, linux-kernel at vger.kernel.org



Someone sent me a private e-mail message suggesting that I apply this
patch that Matthew Dharm posted to the linux-usb-devel list yesterday
and see if that would restore the write throughput to linux-2.4
levels.

The patch limits the size of the transfers, and can be found at

~    http://sourceforge.net/mailarchive/message.php?msg_id=6429200

or right here:

- --- drivers/usb/storage/scsiglue.c.orig    2003-08-09 00:36:46.000000000
- -0400
+++ drivers/usb/storage/scsiglue.c    2003-11-03 16:49:42.000000000 -0500
@@ -315,6 +315,9 @@
~     /* lots of sg segments can be handled */
~     .sg_tablesize =            SG_ALL,

+    /* limit the total size of a transfer to 120 KB */
+    .max_sectors =            240,
+
~     /* merge commands... this seems to help performance, but
~      * periodically someone should test to see which setting is more
~      * optimal.


I am happy to report that this patch has restored the write throughput
to the same speed that it was on linux-2.4.

Problem solved.    Thanks much.

~            -Tim Shepard
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