Docs ModMemCache » History » Revision 3
Revision 2 (Anonymous, 2007-04-24 13:30) → Revision 3/24 (qhy, 2007-04-26 09:15)
{{{ #!rst ================== Memory File Cache ================== --------------------- Module: mod_mem_cache --------------------- .. meta:: :keywords: lighttpd, cache .. contents:: Table of Contents Description =========== Serving several thousands small files for lighttpd Mod_mem_cache is quite challenging. Operating System has to do a lot of random access, which increase io-wait. mod_mem_cache is the plugin which stores content of files in memory for faster serving. It's more configurable than OS buffers (at least, linux buffers), in some cases yields better performance. For example, you can configure it to cache files smaller than 5 kb, just cache files with a specific mime type or different strategies to free memory when the configured limit has been reached. Installation ============ This module is a 3rd party module, is not included in the official distribution. You need to download it from here: * For lighttpd 1.4.13: [http://www.linux.com.cn/tag/mod_mem_cache mod_mem_cache] * For lighttpd 1.4.15: [http://bergstroem.nu/lighttpd-1.4.15.mod_mem_cache.v1.2.patch] (unsupported, straight port from 1.4.13 patch) Options ======= There's not much documentation. See [http://www.linux.com.cn/archives/171.html] mem-cache.filetypes content-type arrays which want to put into memory. e.g.: :: mem-cache.filetypes=("text/css") Default: not set, cache all files mem-cache.enable * mem-cache.enable: enable or disable mod_mem_cache. e.g.: :: mem-cache.enable = "disable" $HTTP["host"] == "images.example.org" { mem-cache.enable = "enable" } Default: mem_cache, default to enable mem-cache.max-memory * mem-cache.max-memory: maxium memory in Mbytes mod-mem-cache can use. Default: used by mod_memcache, default is 512 (means 512 (512 ''Megabytes''). mem-cache.max-file-size * mem-cache.max-file-size: maxium file size in Kbytes of kbytes for single file to cache in memory. Default: file, default is 512 (means 512 ''Kilobytes''). mem-cache.lru-remove-count * mem-cache.lru-remove-count: number of cached memory items to remove when used memory reached maxmemory by LRU algorthim Default: algorthim. default is 200. mem-cache.expire-time memory * mem-cache.expire-time: cache's expire time in minutes. e.g.: :: mem-cache.expire-time = 1440 # 1 day Default: 0 (means default is zero which means to check file update for etag every request) mem-cache.slru-thresold time * mem-cache.filetypes: content-type arrays which want to put into cache content. default is not set which means to cache all types. for examples: mem-cache.filetypes=("text/css") to cache css files only. * mem-cache.slru-thresold: Adjusts slru threshold (against hit counter) Default: counter). Default is 0 (disabled) Example ======= e.g.: :: mem-compress.filetypes = ("application/x-javascript", "text/css", "text/html", "text/javascript") # Cache javascript, css, html file in memory mem-cache.max-memory = 1024 # Use 1G memory cache mem-cache.max-file-size = 1024 # Cache maxium 1M-size file === Additional info concerning SLRU balancing === ========================================= The SLRU has one LRU cache for the probationary segment, one for the protected segment. On the first miss an entry is added to the probationary LRU cache without any data. Only if its hit count increases over threshold it is propagated to the protected LRU cache which has real content. That way you decrease the propability that an entry is kicked out of the LRU cache as you increase the threshold for one entry getting into the cache. In practice, mem-cache.slru-thresold should adjust to archieve higher hit-rate and less memory usage }}}