weighttp (pronounced weighty) is a lightweight and small benchmarking tool for webservers.
It was designed to be very fast and easy to use and only supports a tiny fraction of the HTTP protocol in order to be lean and simple.
weighttp supports multithreading to make good use of modern CPUs with multiple cores as well as asynchronous i/o
for concurrent requests within a single thread.
For event handling, weighty relies on libev which fits the design perfectly, being lightweight and fast itself.
Thanks to that, weighty supports all modern high-performance event interfaces like epoll or kqueue, that the major OSs provide.

Similar tools



Use git to fetch the latest source:

$ git clone git://

or download a .tar.gz from

Binary packages are available from for openSUSE and Debian based distributions:


Use waf (included, needs python) to build:

$ ./waf configure
$ ./waf build

(If you have libraries/includes in special paths, try something like this: LINKFLAGS=-L/opt/local/lib CFLAGS=-I/opt/local/include ./waf configure)

See ./waf --help for available configure options and other commands available.

Alternatively, you can just use gcc directly too (but you will have to (un)install it manually:

$ gcc -g2 -O2 src/*.c -o weighttp -lev -lpthread


Depending on your configure arguments, you might need root to (un)install.

$ ./waf install


$ ./waf uninstall


weighttp uses similar commandline arguments as apache bench (ab):

weighttp <options> <url>
  -n num   number of requests (mandatory)
  -t num   threadcount (default: 1)
  -c num   concurrent clients (default: 1)
  -k       keep alive (default: no)
  -h       show help and exit
  -v       show version and exit


Benchmarking a webserver can result in a lot of sockets being created, especially if you don't use the -k parameter to reuse existing connections.
This can cause your system to run out of TCP port numbers and you will see the following error:

error: connect() failed: Cannot assign requested address (99)

Linux has a hardcoded 60 seconds timeout before it reuses a previously in use port. You can mitigate the problem by tuning 2 kernel parameters:


This allows reusing of sockets which are in the TIME_WAIT state when it is safe from a protocol perspectiv.

echo 1 > /proc/sys/net/ipv4/tcp_tw_reuse

or add "net.ipv4.tcp_tw_reuse = 1" to your /etc/sysctl.conf to make the change permanent. You need to reload it via sysctl /etc/sysctl.conf


This allows fast recycling of sockets which are in the TIME_WAIT state even if it is not safe from a protocol perspective.
You should not use this in a production environment. It can cause issues with loadbalancers and other mayhem.

echo 1 > /proc/sys/net/ipv4/tcp_tw_recycle

or add "net.ipv4.tcp_tw_recycle = 1" to your /etc/sysctl.conf to make the change permanent (bad idea). You need to reload it via sysctl /etc/sysctl.conf