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Date: Wed, 16 Apr 2003 05:45:20 -0400
From: Chuck Ebbert <76306.1226@compuserve.com>
Subject: Re: DMA transfers in 2.5.67
To: Mens Rullgerd <mru@users.sourceforge.net>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
       Alan Cox <alan@lxorguk.ukuu.org.uk>
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> Btw, I just noticed that hard disk throughput is much lower with 2.5
> than 2.4.  With 2.4.21-pre5 I get ~40 MB/s, but with 2.5.67 the speed
> drops to 25-30 MB/s.  Everything according to hdparm.  Is it possible
> that DMA is generally slow for some reason?


  I am seeing that too, with IDE hardware.

  And 2.4.20aa1 is even faster:



# mount /ext3_fs
# time dd if=/ext3_fs/100MiB_file of=/dev/null bs=32k



  2.4.20aa1 : 3.3 sec (exactly what I expect to see)
  2.5.66    : 6.6 sec


--
 Chuck