Apache HTTP Server Version 2.2
This document refers to the 2.2 version of Apache httpd, which is no longer maintained. The active release is documented here. If you have not already upgraded, please follow this link for more information.
You may follow this link to go to the current version of this document.
Available Languages: en
Description: | An experimental variant of the standard worker
MPM |
---|---|
Status: | MPM |
Module Identifier: | mpm_event_module |
Source File: | event.c |
This MPM is experimental, so it may or may not work as expected.
The event
Multi-Processing Module (MPM) is
designed to allow more requests to be served simultaneously by
passing off some processing work to supporting threads, freeing up
the main threads to work on new requests. It is based on the
worker
MPM, which implements a hybrid
multi-process multi-threaded server. Run-time configuration
directives are identical to those provided by
worker
.
To use the event
MPM, add
--with-mpm=event
to the configure
script's arguments when building the httpd
.
This MPM tries to fix the 'keep alive problem' in HTTP. After a client completes the first request, the client can keep the connection open, and send further requests using the same socket. This can save significant overhead in creating TCP connections. However, Apache traditionally keeps an entire child process/thread waiting for data from the client, which brings its own disadvantages. To solve this problem, this MPM uses a dedicated thread to handle both the Listening sockets, and all sockets that are in a Keep Alive state.
The MPM assumes that the underlying apr_pollset
implementation is reasonably threadsafe. This enables the MPM to
avoid excessive high level locking, or having to wake up the listener
thread in order to send it a keep-alive socket. This is currently
only compatible with KQueue and EPoll.
This MPM depends on APR's atomic
compare-and-swap operations for thread synchronization. If you are
compiling for an x86 target and you don't need to support 386s, or
you are compiling for a SPARC and you don't need to run on
pre-UltraSPARC chips, add
--enable-nonportable-atomics=yes
to the
configure
script's arguments. This will cause
APR to implement atomic operations using efficient opcodes not
available in older CPUs.
This MPM does not perform well on older platforms which lack good threading, but the requirement for EPoll or KQueue makes this moot.
libkse
(see man libmap.conf
).glibc
has been compiled
with support for EPoll.Available Languages: en