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This module is contained in the mod_mmap_static.c file, with
Apache 1.3 and later. It provides mmap()ing of a statically configured list
of frequently requested but not changed files. It is not compiled into the
server by default. To use mod_mmap_static you have to enable
the following line in the server build Configuration file:
AddModule modules/experimental/mod_mmap_static.o
This is an experimental module and should be used with
care. You can easily create a broken site using this module, read this
document carefully.
mod_mmap_static maps a list of statically configured files (via
MMapFile directives in the main server configuration) into
memory through the system call mmap(). This system
call is available on most modern Unix derivates, but not on all. There
are sometimes system-specific limits on the size and number of files that
can be mmap()d, experimentation is probably the easiest way to find out.
This mmap()ing is done once at server start or restart, only. So whenever
one of the mapped files changes on the filesystem you have to
restart the server by at least sending it a HUP or USR1 signal (see the
Stopping and Restarting documentation). To
reiterate that point: if the files are modified in place without
restarting the server you may end up serving requests that are completely
bogus. You should update files by unlinking the old copy and putting a new
copy in place. Most tools such as rdist and mv do
this. The reason why this modules doesn't take care of changes to the files
is that this check would need an extra stat() every time which
is a waste and against the intent of I/O reduction.
Syntax: MMapFile filename ...
Default: None
Context: server-config
Override: Not applicable
Status: Experimental
Module: mod_mmap_static
Compatibility: Only available in Apache 1.3 or later
The MMapFile directive maps one or more files (given as
whitespace separated arguments) into memory at server startup time. They
are automatically unmapped on a server shutdown. When the files have changed
on the filesystem at least a HUP or USR1 signal should be send to the server
to re-mmap them.
Be careful with the filename arguments: They have to literally
match the filesystem path Apache's URL-to-filename translation handlers
create. We cannot compare inodes or other stuff to match paths through
symbolic links etc. because that again would cost extra stat()
system calls which is not acceptable. This module may or may not work
with filenames rewritten by mod_alias or
mod_rewrite... it is an experiment after all.
Notice: You cannot use this for speeding up CGI programs or other files which are served by special content handlers. It can only be used for regular files which are usually served by the Apache core content handler.
Example:MMapFile /usr/local/apache/htdocs/index.html
Note: don't bother asking for a for a MMapDir
directive which
recursively maps all the files in a directory. Use Unix the way it was
meant to be used. For example, see the
Include directive, and consider this command:
find /www/htdocs -type f -print \ | sed -e 's/.*/mmapfile &/' > /www/conf/mmap.conf
