i386/74074: hw.ata.wc=0 / but write cache still enabled

[Arne Wörner]

The following reply was made to PR i386/74074; it has been noted by GNATS.

From: Arne "Wörner" <arne_woerner at yahoo.com>
To: freebsd-gnats-submit at freebsd.org
Cc:  
Subject: RE: i386/74074: hw.ata.wc=0 / but write cache still enabled
Date: Mon, 29 Nov 2004 04:38:37 -0800 (PST)

 --- Björn König <bkoenig at cs.tu-berlin.de> wrote:
 > Perform a small benchmark, e.g. with /usr/ports/benchmark/bonnie (bonnie -d
 > /usr -s <twice as much as your RAM>). Perhaps the write cache is turned off,
 > but it's not shown correctly. If your write transfer rates around 10 MB/s
 > then the write cache might be disabled. Show the complete result and tell
 > also your CPU model.
 > 
 I use an AMD Athlon(tm) XP 2400+ (2000MHz).
 
 Here are bonnie's results:
 
 AFTER my "dd if=/dev/ad1 bs=512k count=1000 of=/dev/null"-trick (somehow this
 trick seems to 
 change the write speed dramatically (factor 5; /opt/tmp is on /dev/ad1))
 WITH hw.ata.wc=0:
 neo# bonnie -d /opt/tmp -s 1024 -m Athlon2400
               -------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
 Athlon24 1024 47464 55.1 46720 24.9 17561  9.7 44685 56.0 43861 26.5 146.4  2.8
 
 WITHOUT the "trick"
 AFTER a fresh boot
 WITH hw.ata.wc=1:
 neo# bonnie -d /opt/tmp -s 1024 -m Athlon2400
               -------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
 Athlon24 1024  6540  7.3 47957 23.9 15591 11.6 46357 57.1 44280 23.3 142.4  3.6
 
 AFTER previous test
 WITH hw.ata.wc=1:
               -------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
 Athlon24 1024 46270 57.7 47708 24.4 17995  9.5 44864 55.5 43965 23.5 150.2  2.2
 
 
 AFTER fresh boot
 WITHOUT trick
 WITH hw.ata.wc=0
               -------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
 Athlon24 1024  6570 14.4 47726 24.0 15634 13.7 46413 57.1 43569 15.5 155.6  1.2
 
 AFTER previous test
 WITH hw.ata.wc=0
               -------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
 Athlon24 1024 48619 54.4 46796 37.1 15268 19.7 45892 59.7 44151 16.0 159.8  1.2
 
 
 -Arne
 
 
 
 
 
 	
 		
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