Apache is appalling in memory consumption
a line
And that's just a start. Sometimes it can be 1MB.
Is this normal? How can I optimize Apache better? Before the test I have followed this guide:
And it still consumes so much memory. Even a blank response with nothing more than a status code costs me 150kB of RAM.
I don't know but Apache just seems outrageous in memory usage. If it is so NOT efficient in memory management, why does it get so popular in the first place? There's got be something I'm doing wrong.
FYI, the total number of unique visits to all my sites hosted at my Linode 512MB box is about 6000 - 8000. Some of them are wordpress blogs without cache management and some of them are my own development work. Do I need to upgrade to the 1024 plan?
14 Replies
Replace with Nginx or Lighttpd.
You won't ever look back. your 512mb box should be able to cope easily with that many users if configured properly.
Nginx does perform faster so if you feel like switching it's not a bad thing.
If you don't feel like switching can you post your apache configuration?
> Some of them are wordpress blogs without cache management
There's your #1 culprit. WordPress without caching is just a disaster waiting to happen.
The guide you linked to recommends ServerLimit and MaxClients values of 64 each. If you're OOMing all the time, you should try reducing those values. Set them both to 25-30 and watch your memory consumption go down.
@fiat:
The best way to optimize Apache is by uninstalling it.
Replace with Nginx or Lighttpd.
You won't ever look back. your 512mb box should be able to cope easily with that many users if configured properly.
But do I have to modify my existing code of all the websites (PHP, .htaccess, etc) on a massive scale? Are Lighttpd and Apache fully compatible?
@obs:
I assume you mean 6000-8000 unique visits a day? At most thats one visit every 10 seconds, which is nothing for a 512.
Nginx does perform faster so if you feel like switching it's not a bad thing.
If you don't feel like switching can you post your apache configuration?
Yes, 6k-8k uv/day. Please inspect the configuration file here:
#
# Based upon the NCSA server configuration files originally by Rob McCool.
#
# This is the main Apache server configuration file. It contains the
# configuration directives that give the server its instructions.
# See http://httpd.apache.org/docs/2.2/ for detailed information about
# the directives.
#
# Do NOT simply read the instructions in here without understanding
# what they do. They're here only as hints or reminders. If you are unsure
# consult the online docs. You have been warned.
#
# The configuration directives are grouped into three basic sections:
# 1\. Directives that control the operation of the Apache server process as a
# whole (the 'global environment').
# 2\. Directives that define the parameters of the 'main' or 'default' server,
# which responds to requests that aren't handled by a virtual host.
# These directives also provide default values for the settings
# of all virtual hosts.
# 3\. Settings for virtual hosts, which allow Web requests to be sent to
# different IP addresses or hostnames and have them handled by the
# same Apache server process.
#
# Configuration and logfile names: If the filenames you specify for many
# of the server's control files begin with "/" (or "drive:/" for Win32), the
# server will use that explicit path. If the filenames do *not* begin
# with "/", the value of ServerRoot is prepended -- so "/var/log/apache2/foo.log"
# with ServerRoot set to "" will be interpreted by the
# server as "//var/log/apache2/foo.log".
#
### Section 1: Global Environment
#
# The directives in this section affect the overall operation of Apache,
# such as the number of concurrent requests it can handle or where it
# can find its configuration files.
#
#
# ServerRoot: The top of the directory tree under which the server's
# configuration, error, and log files are kept.
#
# NOTE! If you intend to place this on an NFS (or otherwise network)
# mounted filesystem then please read the LockFile documentation (available
# at <url:http: httpd.apache.org="" docs-2.1="" mod="" mpm_common.html#lockfile="">);
# you will save yourself a lot of trouble.
#
# Do NOT add a slash at the end of the directory path.
#
ServerRoot "/etc/apache2"
#
# The accept serialization lock file MUST BE STORED ON A LOCAL DISK.
#
# <ifmodule !mpm_winnt.c=""># <ifmodule !mpm_netware.c="">LockFile /var/lock/apache2/accept.lock
#</ifmodule>
#</ifmodule>
#
# PidFile: The file in which the server should record its process
# identification number when it starts.
# This needs to be set in /etc/apache2/envvars
#
PidFile ${APACHE_PID_FILE}
#
# Timeout: The number of seconds before receives and sends time out.
#
Timeout 300
#
# KeepAlive: Whether or not to allow persistent connections (more than
# one request per connection). Set to "Off" to deactivate.
#
KeepAlive On
#
# MaxKeepAliveRequests: The maximum number of requests to allow
# during a persistent connection. Set to 0 to allow an unlimited amount.
# We recommend you leave this number high, for maximum performance.
#
MaxKeepAliveRequests 250
#
# KeepAliveTimeout: Number of seconds to wait for the next request from the
# same client on the same connection.
#
KeepAliveTimeout 15
##
## Server-Pool Size Regulation (MPM specific)
##
# prefork MPM
# StartServers: number of server processes to start
# MinSpareServers: minimum number of server processes which are kept spare
# MaxSpareServers: maximum number of server processes which are kept spare
# MaxClients: maximum number of server processes allowed to start
# MaxRequestsPerChild: maximum number of requests a server process serves
<ifmodule mpm_prefork_module="">StartServers 1
MinSpareServers 3
MaxSpareServers 6
ServerLimit 24
MaxClients 24
MaxRequestsPerChild 3000</ifmodule>
# worker MPM
# StartServers: initial number of server processes to start
# MaxClients: maximum number of simultaneous client connections
# MinSpareThreads: minimum number of worker threads which are kept spare
# MaxSpareThreads: maximum number of worker threads which are kept spare
# ThreadsPerChild: constant number of worker threads in each server process
# MaxRequestsPerChild: maximum number of requests a server process serves
<ifmodule mpm_worker_module="">StartServers 1
MaxClients 24
MinSpareThreads 3
MaxSpareThreads 6
ThreadsPerChild 24
MaxRequestsPerChild 3000</ifmodule>
# These need to be set in /etc/apache2/envvars
User ${APACHE_RUN_USER}
Group ${APACHE_RUN_GROUP}
#
# AccessFileName: The name of the file to look for in each directory
# for additional configuration directives. See also the AllowOverride
# directive.
#
AccessFileName .htaccess
#
# The following lines prevent .htaccess and .htpasswd files from being
# viewed by Web clients.
#
<files ~="" "^\.ht"="">Order allow,deny
Deny from all</files>
#
# DefaultType is the default MIME type the server will use for a document
# if it cannot otherwise determine one, such as from filename extensions.
# If your server contains mostly text or HTML documents, "text/plain" is
# a good value. If most of your content is binary, such as applications
# or images, you may want to use "application/octet-stream" instead to
# keep browsers from trying to display binary files as though they are
# text.
#
DefaultType text/plain
#
# HostnameLookups: Log the names of clients or just their IP addresses
# e.g., www.apache.org (on) or 204.62.129.132 (off).
# The default is off because it'd be overall better for the net if people
# had to knowingly turn this feature on, since enabling it means that
# each client request will result in AT LEAST one lookup request to the
# nameserver.
#
HostnameLookups Off
# ErrorLog: The location of the error log file.
# If you do not specify an ErrorLog directive within a <virtualhost># container, error messages relating to that virtual host will be
# logged here. If you *do* define an error logfile for a <virtualhost># container, that host's errors will be logged there and not here.
#
#ErrorLog /var/log/apache2/error.log
ErrorLog /dev/null
#
# LogLevel: Control the number of messages logged to the error_log.
# Possible values include: debug, info, notice, warn, error, crit,
# alert, emerg.
#
LogLevel warn
# Include module configuration:
Include /etc/apache2/mods-enabled/*.load
Include /etc/apache2/mods-enabled/*.conf
# Include all the user configurations:
Include /etc/apache2/httpd.conf
# Include ports listing
Include /etc/apache2/ports.conf
#
# The following directives define some format nicknames for use with
# a CustomLog directive (see below).
# If you are behind a reverse proxy, you might want to change %h into %{X-Forwarded-For}i
#
LogFormat "%v:%p %h %l %u %t "%r" %>s %b "%{Referer}i" "%{User-Agent}i"" vhost_combined
LogFormat "%h %l %u %t "%r" %>s %b "%{Referer}i" "%{User-Agent}i"" combined
LogFormat "%h %l %u %t "%r" %>s %b" common
LogFormat "%{Referer}i -> %U" referer
LogFormat "%{User-agent}i" agent
#
# Define an access log for VirtualHosts that don't define their own logfile
#CustomLog /var/log/apache2/other_vhosts_access.log vhost_combined
CustomLog /dev/null combined
#
# Customizable error responses come in three flavors:
# 1) plain text 2) local redirects 3) external redirects
#
# Some examples:
#ErrorDocument 500 "The server made a boo boo."
#ErrorDocument 404 /missing.html
#ErrorDocument 404 "/cgi-bin/missing_handler.pl"
#ErrorDocument 402 http://www.example.com/subscription_info.html
#
#
# Putting this all together, we can internationalize error responses.
#
# We use Alias to redirect any /error/HTTP_<error>.html.var response to
# our collection of by-error message multi-language collections. We use
# includes to substitute the appropriate text.
#
# You can modify the messages' appearance without changing any of the
# default HTTP_<error>.html.var files by adding the line:
#
# Alias /error/include/ "/your/include/path/"
#
# which allows you to create your own set of files by starting with the
# /usr/share/apache2/error/include/ files and copying them to /your/include/path/,
# even on a per-VirtualHost basis. The default include files will display
# your Apache version number and your ServerAdmin email address regardless
# of the setting of ServerSignature.
#
# The internationalized error documents require mod_alias, mod_include
# and mod_negotiation. To activate them, uncomment the following 30 lines.
# Alias /error/ "/usr/share/apache2/error/"
#
# <directory "="" usr="" share="" apache2="" error"=""># AllowOverride None
# Options IncludesNoExec
# AddOutputFilter Includes html
# AddHandler type-map var
# Order allow,deny
# Allow from all
# LanguagePriority en cs de es fr it nl sv pt-br ro
# ForceLanguagePriority Prefer Fallback
#</directory>
#
# ErrorDocument 400 /error/HTTP_BAD_REQUEST.html.var
# ErrorDocument 401 /error/HTTP_UNAUTHORIZED.html.var
# ErrorDocument 403 /error/HTTP_FORBIDDEN.html.var
# ErrorDocument 404 /error/HTTP_NOT_FOUND.html.var
# ErrorDocument 405 /error/HTTP_METHOD_NOT_ALLOWED.html.var
# ErrorDocument 408 /error/HTTP_REQUEST_TIME_OUT.html.var
# ErrorDocument 410 /error/HTTP_GONE.html.var
# ErrorDocument 411 /error/HTTP_LENGTH_REQUIRED.html.var
# ErrorDocument 412 /error/HTTP_PRECONDITION_FAILED.html.var
# ErrorDocument 413 /error/HTTP_REQUEST_ENTITY_TOO_LARGE.html.var
# ErrorDocument 414 /error/HTTP_REQUEST_URI_TOO_LARGE.html.var
# ErrorDocument 415 /error/HTTP_UNSUPPORTED_MEDIA_TYPE.html.var
# ErrorDocument 500 /error/HTTP_INTERNAL_SERVER_ERROR.html.var
# ErrorDocument 501 /error/HTTP_NOT_IMPLEMENTED.html.var
# ErrorDocument 502 /error/HTTP_BAD_GATEWAY.html.var
# ErrorDocument 503 /error/HTTP_SERVICE_UNAVAILABLE.html.var
# ErrorDocument 506 /error/HTTP_VARIANT_ALSO_VARIES.html.var
# Include of directories ignores editors' and dpkg's backup files,
# see README.Debian for details.
# Include generic snippets of statements
Include /etc/apache2/conf.d/
# Include the virtual host configurations:
Include /etc/apache2/sites-enabled/
ServerName foo</error></error></virtualhost></virtualhost></url:http:>
@hybinet:
> Some of them are wordpress blogs without cache management
There's your #1 culprit. WordPress without caching is just a disaster waiting to happen.The guide you linked to recommends ServerLimit and MaxClients values of 64 each. If you're OOMing all the time, you should try reducing those values. Set them both to 25-30 and watch your memory consumption go down.
Thanks, I'll get a cache plugin installed and see how it goes.
I actually have set both of the values to 24 and OOM still happens.
@ichsie2036:
But do I have to modify my existing code of all the websites (PHP, .htaccess, etc) on a massive scale? Are Lighttpd and Apache fully compatible?
.htaccess only works with Apache, so you'll need to Google some server configurations that have the same effect as an .htaccess file. There are plenty of those for all major open-source apps.
From my experience, it's easier to replicate .htaccess rules with nginx, whereas it's easier to set up PHP with lighttpd. But recent versions of Ubuntu come with spawn-fcgi, so nginx+fastcgi is a breeze to set up.
On the PHP side, nothing needs to be changed unless you're using something very strange.
@ichsie2036:
I actually have set both of the values to 24 and OOM still happens.
Apache might not be the culprit. SSH into your box when you're almost out of memory, run top, and press Shift+M to sort by memory usage. Which programs are using the most RAM? Post the output if possible.
.htaccess type rules are easy enough to implement with lighttpd, there is plenty of documentation available.
Defiantly install caching, php's apc and wordpress' super cache work wonders.
Also what's your mysql memory usage like? In my experience mysql tends to chew more than apache.
I added mod_expire, added rules to expiration for static content and it made the trick for 2 weeks (CPU average = 10% and free memory = 300Kb) but now the issue is back again. My CPU average is up 30% and free memory is just 100Kb (900Kb used all the time). I have plenty of cache configurated for my software, I tested with webpagetest.org (It can help you!) and everything looks good however the problem persists.
I have the same quantity of unique visits than you. If I find anything else that helps me I will tell you.
@msolano:
I added mod_expire, added rules to expiration for static content and it made the trick for 2 weeks (CPU average = 10% and free memory = 300Kb) but now the issue is back again. My CPU average is up 30% and free memory is just 100Kb (900Kb used all the time). I have plenty of cache configurated for my software, I tested with webpagetest.org (It can help you!) and everything looks good however the problem persists.
Are you sure you're actually having memory problems and it's not caching?
@msolano:
My CPU average is up 30% and free memory is just 100Kb (900Kb used all the time).
Have you read
I tuned mysql and added noatime to fstab. Actually my CPU average is 18% and free memoy is 52%
Now I'm very happy. Thank you guys.
@msolano:
glg: I thought I had memory problems because top was showing few free memory but hybinet's link make me feel better, I didn't know about Linux memory management… ok, ok, I'm newbie
:oops:
We all do in the beginning
just remember:
free -m
will show you what's really being used by apps vs caching