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Date: Sat, 4 Oct 2003 22:38:38 -0700
From: Andrew Morton <akpm@osdl.org>
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Cc: jgarzik@pobox.com, lm@bitmover.com, hannal@us.ibm.com,
       lse-tech@lists.sourceforge.net, linux-kernel@vger.kernel.org
Subject: Re: Minutes from 10/1 LSE Call
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insecure <insecure@mail.od.ua> wrote:
>
> So:
>  * we hit a ceiling of ~133 Mb/s, no matter how many disks
>  * CPU utilization is 100%, spent mostly in copy_to_user
>  * RAM bandwidth is >1Gb/s
> 
>  These can't be true at once.

True.  But bear in mind that the data crosses the memory busses up to three
times: disk to pagecache, pagecache to CPU, CPU to user memory.

So top speed may be as little as 300 MB/sec.