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Full Discussion: Buffer Cache
Operating Systems HP-UX Buffer Cache Post 68404 by Perderabo on Saturday 2nd of April 2005 08:43:13 PM
Old 04-02-2005
In most cases, data being transferred between disk and memory goes through the buffer cache. When your program reads a file, the system transfers a large chunck of data into the buffer cache. Then the data is copied into your program. The next read may just need a few more bytes from the same buffer. The kernel tries to predict what buffers you may need and reads them in ahead of time. Write also transfer data to the buffer cache. Some tests show that about 90% of explicit reads and writes are satisfied by the buffer cache. This helps performance a lot.
 

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Cache::SharedMemoryCache(3pm)				User Contributed Perl Documentation			     Cache::SharedMemoryCache(3pm)

NAME
Cache::SharedMemoryCache -- extends the MemoryCache. DESCRIPTION
The SharedMemoryCache extends the MemoryCache class and binds the data store to shared memory so that separate process can use the same cache. The official recommendation is now to use FileCache instead of SharedMemoryCache. The reasons for this include: 1) FileCache provides equal or better performance in all cases that we've been able to test. This is due to all modern OS's ability to buffer and cache file system accesses very well. 2) FileCache has no real limits on cached object size or the number of cached objects, whereas the SharedMemoryCache has limits, and rather low ones at that. 3) FileCache works well on every OS, whereas the SharedMemoryCache works only on systems that support IPC::ShareLite. And IPC::ShareLite is an impressive effort -- but think about how hard it is to get shared memory working properly on *one* system. Now imagine writing a wrapper around shared memory for many operating systems. SYNOPSIS
use Cache::SharedMemoryCache; my %cache_options_= ( 'namespace' => 'MyNamespace', 'default_expires_in' => 600 ); my $shared_memory_cache = new Cache::SharedMemoryCache( \%cache_options ) or croak( "Couldn't instantiate SharedMemoryCache" ); METHODS
See Cache::Cache for the API documentation. OPTIONS
See Cache::Cache for the standard options. PROPERTIES
See Cache::Cache for the default properties. SEE ALSO
Cache::Cache, Cache::MemoryCache AUTHOR
Original author: DeWitt Clinton <dewitt@unto.net> Last author: $Author: dclinton $ Copyright (C) 2001-2003 DeWitt Clinton perl v5.12.4 2009-03-01 Cache::SharedMemoryCache(3pm)
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