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Date: Fri,  5 Mar 1999 02:59:07 -0800 (PST)
From: hokada@isl.melco.co.jp
To: freebsd-gnats-submit@freebsd.org
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Subject: kern/10398: Tagged queueing makes IBM DCAS-34330 slow
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>Number:         10398
>Category:       kern
>Synopsis:       Tagged queueing makes IBM DCAS-34330 slow
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          change-request
>Submitter-Id:   current-users
>Arrival-Date:   Fri Mar  5 03:00:01 PST 1999
>Closed-Date:
>Last-Modified:
>Originator:     Hideaki Okada
>Release:        3.1-RELEASE
>Organization:
MITSUBISHI Electric
>Environment:
FreeBSD waikiki.isl.melco.co.jp 3.1-RELEASE FreeBSD 3.1-RELEASE #5: Sat Feb 20 01:25:27 JST 1999     hokada@waikiki.isl.melco.co.jp:/usr/src/sys/compile/WAIKIKI  i386

>Description:
My IBM DCAS-34330 hard drive is connected to Adaptec AHA-2940 adapter,
and I found write performance is low.
Simple throughput measurement like 'dd if=/dev/zero of=test bs=64k count=1000'
shows ahout 3MB/s even though it should be 7-8MB/s .
However, there is no trouble on read performance.
Here is bonnie's results:

               -------Sequential Output-------- ---Sequential Input-- --Random--
               -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU  /sec %CPU
2.2.8R    100  6677 83.1  7542 22.8  3313 11.3  8519 93.4  7813 14.0 250.0  4.9
3.1R      100  7269 90.7  3199 10.5  2283  8.7  7450 95.7  7548 15.0 262.5  5.4
3.1R(*)   100  7376 91.3  6823 21.5  2628  9.3  6931 88.7  7469 14.3 240.6  4.7

(*) tagged queuing is turned off by modifying cam_xpt.c

>How-To-Repeat:
I reported this on FreeBSD-users-jp@jp.freebsd.org mailing list,
and the other report on this problem is posted.
Its configuration is:
    IBM DCAS-34330W connected to AHA-2940UW

>Fix:
I put initializer of xpt_quirk_table at cam_xpt.c, and I got bonnie's result as reported above.

             {
                     /*
                      * Slow when tagged queueing is enabled. (3MB/sec versus
                      * 8MB/sec.)
                      */
                     { T_DIRECT, SIP_MEDIA_FIXED, "IBM", "DCAS-34330", "S65A" },
                     /*quirks*/0, /*mintags*/0, /*maxtags*/0
             },

>Release-Note:
>Audit-Trail:
>Unformatted:


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