mod_mem_cache config

Problems with the Linux version of XAMPP, questions, comments, and anything related.

mod_mem_cache config

Postby bigpcman » 10. August 2009 01:11

Where is the configuration file for mod_mem_cache? I don't see anything in httpd.conf or any extra config files associated with it.
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Re: mod_mem_cache config

Postby Nobbie » 10. August 2009 08:53

Feel free to insert the configuration lines wherever you want, either directly in httpd.conf or in an external file and include that file in httpd.conf
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Re: mod_mem_cache config

Postby bigpcman » 10. August 2009 12:55

Nobbie wrote:Feel free to insert the configuration lines wherever you want, either directly in httpd.conf or in an external file and include that file in httpd.conf


Thanks.
I noticed the mod_mem_cache module is loaded in the httpd.conf file so I assumed it was "running" using a default configuration. The html web site files do indeed seem to be cached. I guess this must be linux caching the files. Is there a significant performance gain using mod_mem_cache in addition to the linux cache ?

I've read that mod_disk_cache is faster than mod_mem_cache. I wonder if there is a significant performance gain using mod_disk_cache in addition to the linux cache ?
Last edited by bigpcman on 10. August 2009 13:17, edited 1 time in total.
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Re: mod_mem_cache config

Postby Wiedmann » 10. August 2009 13:03

I guess this must be linux caching the files.

Linux is not caching files.

But maybe your browser (or proxy, or web application) is doing this.

so I assumed it was "running" using a default configuration.

Correct. (and the default for mod_cache is to cache nothing)
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Re: mod_mem_cache config

Postby bigpcman » 10. August 2009 13:23

Thanks for your quick reply. You replied faster than I could finish my post.

I added a question about mod_mem_cache vs mod_disk_cache.

Anyway... you commented that linux does not cache files. Seems to me the linux kernel uses a disk file cache to speed up disk access. Am I missing something here?
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Re: mod_mem_cache config

Postby Nobbie » 11. August 2009 13:18

bigpcman wrote:Seems to me the linux kernel uses a disk file cache to speed up disk access. Am I missing something here?


Linux file system (i.e. extfs2/3, reiserfs etc.) is a caching file system, but caching does not take place on file level, but (one layer beyond) on block level. A block is the smallest unit of disk I/O. Block size depends on disk size and number of blocks, it is determined during disk format ("mkfs" command in linux/unix).

The cache is builtin in the file system driver, i.e. in the linux kernel. You cannot configure or modify it, it is used automatically.

As I am not really a fan of stacked cachings (usually the most powerfull caching is done by the OS), i dont think that there is a measurable performance gain by using several stacking algorithms at different levels/layers. You should run some benchmarks on your system to find out, if additional caching really raises performanceof your webserver.
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