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From: Benjamin LaHaise <bcrl@redhat.com>
To: dean gaudet <dean-list-linux-kernel@arctic.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: 3x slower file reading oddity
Date: Mon, 17 Jun 2002 16:07:57 -0400	[thread overview]
Message-ID: <20020617160757.C1457@redhat.com> (raw)
In-Reply-To: <Pine.LNX.4.44.0206171246270.31265-100000@twinlark.arctic.org>; from dean-list-linux-kernel@arctic.org on Mon, Jun 17, 2002 at 01:03:15PM -0700

On Mon, Jun 17, 2002 at 01:03:15PM -0700, dean gaudet wrote:
> 3x slower with the two cats in parallel.

cat uses an incredibly small buffer for file io (4KB on x86), so 
running multiple cats in parallel will simply thrash your disk.  
What you really want is to run the open()s in parallel and the 
read()s sequentially (or in parallel with a large buffer to cut 
down on the seek cost).

		-ben
-- 
"You will be reincarnated as a toad; and you will be much happier."

  reply	other threads:[~2002-06-17 20:07 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-06-17 20:03 3x slower file reading oddity dean gaudet
2002-06-17 20:07 ` Benjamin LaHaise [this message]
2002-06-17 20:31   ` dean gaudet
2002-06-17 23:26 ` Andrew Morton
2002-06-18  0:15   ` dean gaudet
2002-06-18  0:36     ` Andrew Morton
2002-06-18  1:40       ` dean gaudet
2002-06-18  1:45       ` Andreas Dilger
2002-06-18  2:08         ` dean gaudet
2002-06-18 10:45           ` Padraig Brady

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