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Date: Sat, 27 Jul 2002 17:50:17 -0300 (BRT)
From: Rik van Riel <riel@conectiva.com.br>
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To: Buddy Lumpkin <b.lumpkin@attbi.com>
cc: Ville Herva <vherva@niksula.hut.fi>, DervishD <raul@pleyades.net>,
       Linux-kernel <linux-kernel@vger.kernel.org>
Subject: RE: About the need of a swap area
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On Sat, 27 Jul 2002, Buddy Lumpkin wrote:

> >Much more.
> >
> >The latency difference seems to be on the order of 100000 times.
> >It is the latency we care about because that determines how long
> >the CPU cannot do anything useful but has to wait.
>
> And if you look at the ratio between the access time of ram which is in
> the low nanoseconds (1* 10 ^ -9) ... and compare it to the seek +
> rotational delay of a discrete spindal which is in low milliseconds (1*
> 10 ^ -3) that puts you at a ratio of about 1000000.

Indeed.

Now imagine one in every million memory accesses results in
a major page fault ... your computer would run at 1/2 speed.

The difference between a 99.999% hit rate and 99.9999% hit
rate becomes rather important with these latency ratios ;)

regards,

Rik
-- 
Bravely reimplemented by the knights who say "NIH".

http://www.surriel.com/		http://distro.conectiva.com/

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