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From: Apache Wiki <wikidiffs@apache.org>
To: Apache Wiki <wikidiffs@apache.org>
Date: Tue, 16 Nov 2010 11:06:44 -0000
Message-ID: <20101116110644.51113.35565@eosnew.apache.org>
Subject: 
 =?utf-8?q?=5BHttpd_Wiki=5D_Update_of_=22PerformanceScalingUp=22_by_jmcg?=

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The "PerformanceScalingUp" page has been changed by jmcg.
http://wiki.apache.org/httpd/PerformanceScalingUp?action=3Ddiff&rev1=3D1&re=
v2=3D2

--------------------------------------------------

  =

  See also: http://wiki.apache.org/httpd/PerformanceScalingOut
  =

+ =3D 1     Introduction =3D
+ The Performance Tuning page in the Apache 1.3 documentation says:
+ =

+        =E2=80=9CApache is a general webserver, which is designed to be co=
rrect first,
+        and fast second. Even so, its performance is quite satisfactory. M=
ost
+        sites have less than 10Mbits of outgoing bandwidth, which Apache
+        can fill using only a low end Pentium-based webserver.=E2=80=9D
+ =

+  However, this sentence was written a few years ago, and in the meantime
+  several things have happened. On one hand, web server hardware has become
+  much faster. On the other hand, many sites now are allowed much more than
+  ten megabits per second of outgoing bandwidth. In addition, web applicat=
ions
+  have become more complex. The classic brochureware site is alive and wel=
l,
+  but the web has grown up substantially as a computing application platfo=
rm
+  and webmasters may find themselves running dynamic content in Perl, PHP =
or
+  Java, all of which take a toll on performance.
+ =

+  Therefore, in spite of strides forward in machine speed and bandwidth al-
+  lowances, web server performance and web application performance remain =
ar-
+  eas of concern. In this paper and the ApacheCon session it accompanies, =
several
+  aspects of web server performance will be discussed.
+ =

+ =3D=3D 1.1    What Will and Will Not Be Discussed =3D=3D
+ The session will focus on easily accessible configuration and tuning opti=
ons for
+  Apache 1.3 and 2 as well as monitoring tools. Monitoring tools will allo=
w you
+  to observe your web server to gather information about its performance, =
or
+  lack thereof. We=E2=80=99ll assume that you don=E2=80=99t have an unlimi=
ted budget for server
+  hardware, so the existing infrastructure will have to do the job. You ha=
ve
+  no desire to compile your own Apache, or to recompile the operating syst=
em
+  kernel. We do assume, though, that you have some familiarity with the Ap=
ache
+  configuration file.
+ =

+ =3D 2      Monitoring Your Server =3D
+ The first task when sizing or performance-tuning your server is to find o=
ut how
+  your system is currently performing. By monitoring your server under rea=
l-world
+  load, or artificially generated load, you can extrapolate its behavior u=
nder stress,
+  such as when your site is mentioned on Slashdot.
+ =

+ =3D=3D 2.1      Monitoring Tools =3D=3D
+ =3D=3D=3D 2.1.1     top =3D=3D=3D
+ The top tool ships with Linux and FreeBSD, and can be downloaded for So-
+  laris2 . It collects a number of statistics for the system and for each =
running
+  process, then displays them interactively on your terminal. The data dis=
played
+  is refreshed every second and varies by platform, but typically includes=
 system
+  load average, number of processes and their current states, the percent =
CPU(s)
+  time spent executing user and system code, and the state of the virtual =
mem-
+  ory system. The data displayed for each process is typically configurabl=
e and
+  includes its process name and ID, priority and nice values, memory footp=
rint,
+  and percentage CPU usage. An example top display is shown in Figure 1.
+ =

+ Top is a wonderful tool even though it=E2=80=99s slightly resource intens=
ive (when
+  running, its own process is usually in the top ten CPU gluttons). It is =
indis-
+  pensable in determining the size of a running process, which comes in ha=
ndy
+  when determining how many server processes you can run on your machine.
+  How to do this is described in Section 3.1.3. Top is, however, an intera=
ctive tool
+  and running it continuously has few if any advantages.
+ =

+ =3D=3D=3D 2.1.2     free =3D=3D=3D
+ This command is only available on Linux. It shows how much memory and swap
+  space is in use. Linux allocates unused memory as file system cache. The=
 free
+  command shows usage both with and without this cache. The free command
+  can be used to find out how much memory the operating system is using, as
+ =

+ described in the paragraph =E2=80=98Sizing MaxClients=E2=80=99 on page 10=
. The output of free
+  looks like this:
+ =

+ {{{
+ sctemme@brutus:~$ free
+ }}}
+ {{{
+               total       used     free   shared    buffers    cached
+ }}}
+ {{{
+ Mem:        4026028    3901892   124136         0    253144    841044
+ }}}
+ {{{
+ -/+ buffers/cache:     2807704  1218324
+ }}}
+ {{{
+ Swap:       3903784      12540  3891244
+ }}}
+=20

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