Web Server Performance Tuning

Web Server Performance Tuning Notes, Nov 2001
(c) EarthLink, Inc. 2001

I want to thank EarthLink for giving me time to prepare the talk.
However as a sysadmin, I kept getting interrupts, but I was able
to put the below together, I hope it's of use to you.

Aleksey Tsalolikhin
1 Nov 2001
eesti@corp.earthlink.net

Web server performance tuning philosophy:

1. use dedicated server ( stability/performance )
Max out on mem, CPU.

2. Set httpd controls (for things like max simultaneous connections)
very high. Don't want to create an artificial bottleneck. This will
put the bottleneck somewhere in the system (Like not enough memory or
CPU, or some OS resource limitation.) When you hit some bottleneck,
tune your website and your httpd config, then your OS, then upgrade
server (or add more servers).

3. KNOW your performance characteristics. Track you server latency.
Make graphs, etc. Recognize when your numbers start drifting up.

Apache httpd.conf, example of things to tune:

StartServers should be pretty high, so you start lots of servers
when server is started.

MaxClients - crank it up to 256 (make sure you have the memory)
If you get lots of traffic, edit HARD_SERVER_LIMIT in src/include/httpd.h,
and raise it to 1024 or higher, and recompile.

MaxRequestsPerChild - set to 10000 to be safe from libraries leaking

FancyIndexing - off (disable the pretty icons in directory listings)

Timeout (timeout to get a TCP ACK or a complete GET request)
default 300 seconds is too long on modern networks - try 60
or 120.

StartServers default is 5, for a dedicated server, make higher
(on a dedicated server, just set to MaxClients, so the parent
doesn't have to tune it up as the requests come in; or half
of MaxClients or more - definitely more than 5 though.)

Links:
http://httpd.apache.org/docs/misc/perf-tuning.html
http://httpd.apache.org/docs/misc/perf.html
http://perl.apache.org/guide/performance.html

Other load-testing or perf measurement software:
httperf http://www.hpl.hp.com/personal/David_Mosberger/httperf.html
http_ping http://www.acme.com/software/http_ping/
torture http://stein.cshl.org/~lstein/torture/torture.html


ab (from Apache distribution, in the bin directory - Apache Bench(mark).)
==
Two ways to run it: conventional (with -c and -n) and
single-sample (ab -n 1 http://...).

Single-sample way is good for minding server latency on
production servers. (Can't load-test production servers.)

Get a lot of samples. This way unusual spikes or dips become
unweighted. Sample regularly - minutely.

Look at avg and mean. When starting tuning, they'll be far apart
(avg will be higher because of spikes). As you progress, and
get rid of/reduce the spikes, the avg and mean will drift closer
together.

run ab -n 1 on same network segment to get server latency
(otherwise you get server + network latency)

--------------------------------------------------------
"truss httpd -X"

runs httpd in single-process mode, so you can truss it easily.
hit it with your Web browser and see if there are any system
cools that look extra or unnecessary - config change can fix
it sometimes.

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

"ndd /dev/tcp \?" shows all TCP stack tunables
(same for /dev/ip and /dev/upd, BTW)

tcp_conn_req_max_q0 - incomplete connections queue (SYN received)
tcp_conn_req_max_q - complete connections queue (handshake done,
waiting to be accept()'ed)

the separation into two queues is a defense against SYN flood attacks.
q0 is usually much larger than q

defaults (in Solaris 8) are:
q0: 4096
q: 128

One can increase these:
example# ndd /dev/tcp tcp_conn_req_max_q0 131072
example# ndd /dev/tcp tcp_conn_req_max_q 1024
example#

use "ndd /dev/tcp tcp_listen_hash" right-most column to see
if you're hitting the queue max

Other things to tune for a busy web server might be

tcp_conn_hash_size (an /etc/system paramater - default is 512,
can change to 1024 or more)

rlim_fd_max (per-process file descriptor limit)


Links:
Solaris Tunable Parameters Manual -
http://docs.sun.com:80/ab2/coll.707.1/SOLTUNEPARAMREF/@Ab2TocView?Ab2Lang=C&Ab2Enc=iso-8859-1
http://www.sean.de/Solaris
http://www.sunperf.com/

Linux performance tuning links:
http://linuxperf.nl.linux.org/


When doing performance tuning, it's important to have
quantified measurement of performance. Use ab, don't fly blind.

---

What to aim for, with regard to web server response time? >200 ms is
potentially problematic, try and keep it under 100 ms, the lower the better.

---
Time::HiRes module for benchmarking - useful for monitoring
response latencies of back-end tiers. perlipc man page from
perl distribution has nice example of perl TCP/IP client you
can hack up and use with Time::HiRes to time TCP/IP client-server
sessions.

文章来自: 本站原创
标签: SERVER  Tuning performance Web