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From Brian Behlendorf <br...@organic.com>
Subject Re: Want to add file caching to Apache
Date Fri, 21 Nov 1997 02:27:15 GMT

>From a contact at Microsoft:

>If you do add file caching to apache, make sure to leave a way not to do
>this on NT.  File caching comes for free when you use the Win32 functions
>like TransmitFile, etc that we have talked about using for Apache 2.0.  To
>manage the file cache you setup a file handle cache, closing file handles
>when you do not need the file in cache and keeping open the ones you do want
>in cache.  Implementing a separate file cache would move the file cache out
>of the kernel into user space and would force copies of the file date, which
>is very CPU expensive...
>
>The implementation below is sometimes called file shadowing, Netscape
>implements it (I think).  What we have seen is that this adds about 5%
>performance increase when all data can fit into RAM, and about a 40%
>performance penalty (at least on NT, don't know about other OSes) when there
>is more active data than RAM, because it requires extra file copies, etc.


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"it's a big world, with lots of records to play." - sig   brian@organic.com

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